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In the last few decennium, the acquaintance between algebraic hyperstructures and fuzzy sets have been considered for its theoretical as well as applications in various fields. Fuzzy hyperstructures are fascinating research topic and substantial amount of researches have been undergoing as of now. As a consequence, fuzzy hyperlattice was introduced by Pengfei He, Xiaolong Xin. But the applications on fuzzy hyperlattice are not defined so far. By scrutinizing the fuzzy hyperlattice, our objective is to present some applications of fuzzy hyperlattice in Biological and Physical Sciences. We find the first and second applications in dihybrid cross of Drosophila melanogaster (housefly) and Pisum sativum (Peas), respectively. Third application is in particle Physics (Elementary particles interaction).

This experiment was conducted to assess the effect of chicken genotype on the growth performance, feed intake and feed efficiency of the progenies resulting from pure, straight and reciprocal cross of Giriraja (Gr) and Alpha chickens. Data obtained on body weight, body length, breast girth, keel length, feed intake and feed efficiency were analyzed using general linear models analysis of variance. Generally, all growth traits and feed consumption characteristics were significantly affected (P < 0.05) by chicken genotype. Growth traits and feed intake increased as birds advanced in age. Giriraja X Giriraja purebred chickens had the highest body weight, breast girth, feed intake and feed conversion efficiency through out the experimental period. However, the progenies resulting from the reciprocal crosses of Alpha X Gr had significant higher body weight and keel. Also, the feed conversion efficiency of the reciprocal crosses were better than the dihybrid cross progenies. The results therefore suggest that the superiority exhibited by the Giriraja could be utilized to improve the growth performance of the indigenous chicken thereby speed up desirable progress in the improvement of the indigenous broiler line. Key words: Chicken, Crossbred, Feed consumption, Genotype, Growth trait, Purebred

Rice can form not only white, but also red, brown and black kernels. In black rice pericarp contains anthocyanin pigment, which has antioxidant activity and is beneficial to human health. The article is devoted to the development of new rice lines with black pericarp on the basis of the hybrid ‘Svetly × Mavr’. The purpose of the work is to develop rice new lines with black seed vessel on the genetic background of the variety ‘Svetly’. There has been carried out a genetic analysis of varying quantitative traits that affect rice productivity. Cleavage by pericarp color occurred according to the dihybrid scheme according to the type of recessive epistasis in the ratio 9:3:4. The black color of the pericarp was formed with the presence of two dominant Pb and Pp genes in the genotype, the brown one was determined by the Pb gene, and the white one was determined by the other combinations of genes. Inheritance of plant height occurred according to the overdominance of large values of the trait. Parental forms differed in the allelic state of two pairs of genes. Along the panicle length, there has been determined partial negative dominance and monogenic differences of the hybridized varieties. According to ‘number of spikelets per panicle’, there has been identified an overdominance of a larger value of the trait and the interaction of two pairs of genes. According to ‘1000-kernel weight’, there has been established partial dominance of large values of the trait and monogenic differences of the initial parental forms. There have been selected the best recombinant forms combining a compact erect panicle and grains with a black seed vessel, and there has been developed starting material for practical breeding. The study was carried out on the fields of the Experimental Station “Proletarskaya” of the Rostov Region in 2018.

Long use of the methods of direct intraspecies hybridization in the selective breeding of varieties of Triticum aestivum L. has led to narrowing of their gene fund and close similarity of the genetic potential of their selective breeding traits. Using the method of experimental mutagenesis, one can induce systemic mutants with features of other hexaploid Triticum species which can freely cross-breed with other hybridization offspring, contributing to extension of genetic potential of cultivated wheat and creation of varieties with new levels of manifestation of economically beneficial traits. We studied the pattern of inheritance of morphological traits of the ear, length of the stem and the elements of productivity of speltoid chemomutant of T. aestivum. For the genetic analysis we used hybrids F1 and F2 of soft wheat obtained by cross-breeding speltoid macromutant (Smuhlianka speltoid), induced by the impact of aqueous solution of N-nitroso-N-methylurea (NMU) in the concentration of 0.025% on the seeds of Smuhlianka variety, with plants of Smuhlianka variety (Erythrospermum variety) and Podoloanka (Lutescens variety). To determine the pattern of inheritance the spike morphology, length of the stem and the elements of productivity in F1 hybrids, we calculated the extent of phenotype domination. In populations of F2, we examined plants with different combinations of phenotype manifestation of ear morphology. In F1 hybrids, the speltoid shape of the ear, absence of awns and red colour of the glumes indicated the dominant pattern of inheritance. The high level of phenotype domination of length of the stem and ear, number of spikelets in the main ear indicates the inheritance of the features according to intermediate, partly dominant and over-dominant types. Taking into account the segregation according to the features of spike morphology, awnedness and colour of glumes, the plants of F2 population were divided into phenotype classes, that is 12 and 6 in the combinations of respectively Smuhlianka speltoid × Smuhlianka and Smuhlianka speltoid × Podolianka. We determined that the obtained results are the consequences of dihybrid linkage which corresponds to the theoretical proportion of 12 : 3 : 1. Segregation into non-aristate and aristate plants corresponds to the proportion of monogene segregation of 3 : 1. Within separately distinguished phenotype classes, no independent inheritance of the shape of the ear and awnedness was observed. Dihybrid segregation of F2 plants into speltoid, squarehead and varieties Lutescence/Erythrospermum with quantitative superiority of speltoid plants suggests the control of the trait by two non-allele genes with epistatic interaction. The red colour of the glumes indicates the dominant monogenic pattern of inheritance. Absence of independent inheritance of the shape of the ear and awnedness indicates localization of genes which determine these features in one chromosome.

The character of inheritance of the morphological traits of spike and grain color and morphometric parameters of the grain in simple and backcross F1 and F2 hybrids of spelt and soft wheat has been investigated. The experiments confirmed that single homologous genes determine the trait of grain width in different species of wheat. Incomplete dominance of the gene that determines the trait of grain length has been revealed. The increase of the dosage of genes from one wheat species in a backcross hybrid has been shown to increase the deviation from the other species and to bring the values of the quantitative parameters of the grain closer to the values for the saturating species. Splitting of the spike color trait in the F2 offspring has been shown to follow the 15: 1 dihybrid cross scheme and to be controlled by two dominant homologous genes.

The aim and tasks of the study . To establish patterns in the inheritance of grain hardness in collection bread winter wheat accessions. Results and discussion . The data demonstrate different nature of the grain hardness inheritance in F 1 , namely: intermediate inheritance, positive dominance and negative dominance (hp = from 1 to - 1). Of 24 F 1 hybrids, 13 had intermediate inheritance, 7 hybrid combinations had negative dominance, and positive dominance was observed in 4 combinations. Depending on the parent genotypes, the grain hardness segregation in F 2 was in accordance with the mono-, di- or three-hybrid scheme. Endosperm texture was mainly formed by additive polymeria. The grain hardness segregation in F 2 and the phenotype distribution occurred depending on the genotypic composition of parents. Conclusions . The nature of the grain hardness inheritance in F 1 hybrids was established; it occurred according to the following types: intermediate inheritance (54.2%), negative dominance (29.2%) and positive dominance (16.7): hp = 1 − -1. The female effect was also established for the endosperm texture formation in F 1 hybrid grain. Analyzing F 2 hybrid grain, we noticed the greatest number of combinations segregated by dihybrid scheme: 15: 1, 9: 7, 7: 9 (66.7%). Three-hybrid type of segregation was observed in 6 combinations (25%); monogenic - in 2 (8.3%)

Children with malformations of cortical development (MCD) are at risk for epilepsy, developmental delays, behavioral disorders, and intellectual disabilities. For a subset of these children, antiseizure medications or epilepsy surgery may result in seizure freedom. However, there are limited options for treating or curing the other conditions, and epilepsy surgery is not an option in all cases of pharmacoresistant epilepsy. Understanding the genetic and neurobiological mechanisms underlying MCD is a necessary step in elucidating novel therapeutic targets. The tish (telencephalic internal structural heterotopia) rat is a unique model of MCD with spontaneous seizures, but the underlying genetic mutation(s) have remained unknown. DNA and RNA-sequencing revealed that a deletion encompassing a previously unannotated first exon markedly diminished Eml1 transcript and protein abundance in the tish brain. Developmental electrographic characterization of the tish rat revealed early-onset of spontaneous spike-wave discharge (SWD) bursts beginning at postnatal day (P) 17. A dihybrid cross demonstrated that the mutant Eml1 allele segregates with the observed dysplastic cortex and the early-onset SWD bursts in monogenic autosomal recessive frequencies. Our data link the development of the bilateral, heterotopic dysplastic cortex of the tish rat to a deletion in Eml1.

Safflower is a minor oilseed crop. It has red, orange, yellow and white flowers which colouring agents used to be natural colour source. Nowadays there is no agreement between researchers about inheritance of corolla colour in safflower. Our aim was to find out interactions character of genes in generating corolla colour. The experiments were held in 2009–2015 with 13 samples of IOC NAAS collection. 2 monohybrid, 11 dihybrid and 2 trihybrid crosses were analysed. It was shown the genes coding corolla colour of safflower form interactions such as: 1) genes O and R interact complementarily forming new sign of orange corolla colour with individual manifestation of each of them of yellow and red colour accordingly; 2) gene C forms dominant epistatic interactions with genes O and R with individual manifestation of yellow corolla colour; 3) gene Y forms recessive epistatic interactions with genes O, R and C without individual manifestation. Recessive homozygote in it makes white corolla colour. Refs 17. Tables 3.

A grapevine hybrid progeny was generated to track the inheritance of the Ren1 and the Run1 powdery mildew resistance alleles and the segregation of the powdery mildew resistance phenotype. Genotypic analysis was carried out using flanking microsatellite markers; phenotypic evaluations were done under in vitro and greenhouse conditions. Pairing the phenotypic and genotypic data demonstrated that Ren1 and Run1 acted as single dominant loci and assorted independently without considerable distortion of segregation. Chromosomal recombination events were detected in the Ren1 but not in the Run1 region, corroborating earlier observations that crossover between homologous chromosomes was suppressed around the Run1 locus. Taken together, the results confirmed that microsatellite marker-assisted selection is a reliable and expeditious method to combine multiple alleles that confer resistance to a pathogen.

Capsicum annuum has been known for the amount of variability present in the genus for fruit traits and also for other morphological traits. The present study used F1 and F2 generations developed from diverse parental stocks to report the inheritance pattern for different fruits traits. Our results demonstrate that pepper fruit bearing habit, its colour at unripe stage and fruit apex are simply inherited traits with or without epistatic interactions while fruit length is a quantitative character. Fruit orientation(drooping or erect) and fruit habit (solitary or cluster)showed segregation ratio of 3: 1 indicating monogenic inheritance of the trait where drooping character was dominant in nature over erect type and solitary fruit type was dominant over cluster type, fruit bearing habit (single pendant, single erect, cluster pendant and cluster erect) exhibited typical dihybrid ratio of 9: 3: 3: 1, fruit colour at unripe stage (green, purple and mixture of green & purple) segregated in the ratio of 9: 3: 4 exhibiting recessive gene epistasis and fruit apex (acute or blunt) showed a ratio of 15: 1 indicating duplicate dominant gene epistasis. Fruit length exhibited quantitative inheritance with plants showing fruit length greater than the positive parent (parent showing higher fruit length among the two parents) and lesser than the negative parent (parent showing lesser fruit length among the two parents) from different crosses. These results provide new data to clarify and further add on to the information available on the inheritance of chilli pepper fruit attributes.

Two artificial pigmentation mutants of Porphyra yezoensis, the green mutant IBY-G1 and the red mutant IBY-R1, were genetically characterized based on the results of cross experiments. The cross between the green mutant and the wild-type HG-511 and the cross between the red mutant and the wild type respectively produced the wild-type heterozygous conchocelis. Zygotospores from the heterozygous conchocelis developed into sectored F1 gametophytic blades (chimeras) in high frequency composed of parental color sectors in both crosses. The segregation ratios of the wild-type sectors and the mutant (green or red) sectors were approximately 1:1. These results suggest that both the green mutant and the red mutant are controlled by a single recessive nuclear gene. The reciprocal cross between the green mutant and the red mutant also produced the wild-type heterozygous conchocelis that is considered to be a dihybrid resulting from complementation of the green mutant gene and the red mutant gene. Zygotospores from the heterozygous conchocelis also produced sectored F1 gametophytic blades in high frequency composed of parental color (green and red) sectors and non-parental color (wild-type and yellowish green) sectors. The segregation ratios of parental color sectors and non-parental color sectors were approximately 1:1. Therefore, it is inferred that the green mutant gene and the red mutant gene are on different chromosomes, and that the wild-type and the yellowish green color sectors are produced by chromosome recombination. These genetic analyses demonstrate that the two artificial mutants are useful as genetic markers for cross breeding of cultivated Porphyra.

[ILLUSTRATION OMITTED] Chromosomal aneuploidy, a deviation from an exact multiple of an organism's haploid chromosome number, is a difficult concept for students to master. Aneuploidy arising from chromosomal non-disjunction (NDJ) is particularly problematic for students, since it arises in the context of meiosis, itself a challenging subject. Students learning NDJ are forced to actively apply their knowledge of normal meiosis, often revealing previously unapparent deficits in their understanding. Teaching NDJ is thus an important opportunity for students to review and apply their skills in modeling meiosis. Despite this opportunity, standard methods for teaching NDJ are passive. While experiments illustrating recombination mapping, sex-linkage, and other core genetics concepts are readily available for high school and undergraduate genetics courses, simple exercises demonstrating NDJ are not. This is regrettable, for non-disjunction is not only medically important but also historically significant as the original proof for the chromosomal theory of inheritance (Bridges, 1916). Presented here is a straightforward method to detect NDJ of the sex chromosomes in Drosophila in the context of laboratory exercises to examine recombination of sex-linked loci. The exercises presented here allow for detecting maternal and paternal NDJ events within a single cross, an advantage since the use of standard markers obscures paternal NDJ events (Bridges, 1916). An additional advantage of this method is that it easily allows for recombination mapping with recessive alleles in trans as well as in cis. This method allows students to simultaneously investigate recombination and aneuploidy with live organisms, and as such is complementary to theoretical methods of teaching recombination and NDJ. The exercises presented here are based on a Drosophila virginizing system that has recently been developed as a method to perform teaching crosses without the need for collecting virgins manually (Venema, 2006). This system employs a modified Y chromosome that harbors a conditional, dominant lethal mutation: a regulatory sequence that is activated in response to heat connected to a protein called head involution defective, or "hid" that activates programmed cell death. Since this modified Y chromosome (abbreviated as Y{hs-hid}) is present only in males, temporarily raising the temperature of a Y{hs-hid} Drosophila culture during larval stages will cause all males to undergo systemic apoptosis and die. Female larvae, however, survive the heat shock and remain virgin after hatching since there are no surviving males to mate with (Venema, 2006). The use of this system is of great advantage for educators in that large numbers of virgins can be obtained without scoring or segregating young female flies. This ability to use large numbers of flies in pedagogical crosses also facilitates finding the results of rare genetic events in the progeny. (1) Venema (2006) describes a scheme for recombination mapping between autosomal loci using this system; however, recombination mapping of sex-linked loci in Drosophila is more convenient for high school or introductory-level university courses. Additionally, examining recombination between sex-linked loci allows for the simultaneous detection of chromosomal NDJ events in the progeny, since some Drosophila sex chromosome aneuploids are viable (Table 1). Four possible exercises are presented: two versions of a dihybrid testcross and two versions of a three-point testcross. The dihybrid testcross exercises map sex-linked loci with the recessive mutant alleles either together as a parental genotype (i.e., recessive alleles in cis) or with recessive mutations inherited from both parents (recessive alleles in trans). Similarly, the options for the three-point testcross are mapping the three loci with mutant alleles all in cis, or with two in cis, and the third in trans. The dihybrid or three-point testcross options allow for instructors to choose the exercises of appropriate complexity for their particular grade level and learning objectives. …

The inheritance patterns of three mutants (light blue body color, dark [French] blue body color, and white eye color) of Procambarus clarkii were determined. All were initially discovered in specimens in nature which were subsequently inbred for six to eight generations in the laboratory to determine inheritance patterns. The light blue body color allele, in which specimens appear powder blue and have reduced numbers of chromatophores, was found to transmit as a simple recessive allele to normal body color. The allele for French blue body color is recessive to its normal allele also, but is known only in females. Homozygosity for the French blue allele is apparently lethal to males. Male carriers for the allele have normal pigmentation. The body color of both alleles is partially due to a carotenoid pigment conjugated with protein. The pigment is tentaively identified as crustacyanin which partially replaces the normal astaxanthin in the exoskeleton which retains its blue color when shed in molting. The white eye phenotype results from the absence of distal and retinular screening pigments. The accessory pigments around the bases of the rhabdoms are still present and appear white in reflected light and pinkish brown in transmitted light. The white eye allele is inherited as a simple recessive mutant allele. Specimens with this allele do not see well in bright light but function normally in dim light. Reciprocal dihybrid crosses of these three mutants showed no evidence of linkage. Field records of mutants and estimates of frequency (white eye color) in natural populations are discussed.

The interactive competence of a number of genes promoting lateral floret development in barley was studied with particular reference to the interaction in dihybrid and trihybrid F2 segregations after crossing involving the six-row locus hex-v and the three most frequently mutating recessive intermedium loci. int-a, int-c. and int-e. The former locus was represented by the mutation hex-v3 (derived from the two-row variety ‘Bonus’) and the allelic state hex-vA in the six-row commercial variety ‘Agneta’. The latter loci were each represented by three allcles (-a9, -a10 -a27; -c5 -c13 -c29; -e20-e23 -e65) derived from the two-row varieties ‘Bonus’ or ‘Foma’, whereas ‘Agneta’ contributed the int-c allele -cA. F2 data for lateral floret characters (awn length. fertility, seed size) were contrasted to standards considered to provide the phenotypic spectra corresponding to the different genotypic constituents of the F2 segregations. The analyses of observed data in relation to expectations on various hypotheses for interaction between hex-v and the recessive int genes led to the following main conclusions. In no case were there indications of total failure to enhance the phenotypic expression above the level of the corresponding standard categories. The degrees of phenotypic enhancement may differ among characters of lateral floret development, among int loci, and among allelic states of the latter, whereas differences between the two representatives of hex-v were not discernible.

Totally 13 intermedium mutants belonging to the more or less pronouncedly dominant locus Int-d of barley have been crossed to mutant representatives of 8 recessive int loci, and the dihybrid F2 classification patterns were analysed for deviations from ratios expected for gene combinations where previous analyses have excluded linkage as a disturbing factor. Among the present 98 combinations between lnt-d alleles and the 8 int loci, 40 indicated, with statistical significance, an enhancement of lateral floret development in double heterozygotes, leading to their being classed as intermedium D. The three Int-d alleles ranking in the top in this respect, d40, d36, and d50, are those showing the most pronounced degrees of dominance, which could indicate that the stronger the basic effect produced by the heterozygote Int-d gene, the more efficiently will a recessive int gene in heterozygote state be able to exert a reinforcement of the phenotypic expression. In the constellation of a heterozygote lnt-d allele and a homozygote recessive gene, tendencies to epistatic interaction (leading to the intermedium D phenotype), or, less frequently, to complementary interaction (leading to the double mutant phenotype) were observed, with a fairly even distribution to the 13 lnt-d alleles. Among the recessive int loci, int-c turned out to be the most efficient, both as enhancer in double heterozygote constellations with Int-d, and in the complementary interaction in the Dd cc gene constellation.

Classification des dihybrides F2 pour la deviation des taux attendus dans les combinaisons de gene en absence de linkage etudie par croisement entre 56 mutants intermedium appartenant a 8 loci int

Studies have reported a wide range of inflammatory responses in the nerve, skin and plasma of leprosy patients. The expression levels of each biomolecule was individualistic, however could be categorized as high and low based on their statistical mean level. Here we report for the first time, expression of a set of biomolecules relating with each other in a defined proportion. The hypothesis of this paper is that the segregation of high and low combinations of a set of biomolecules follows either classical Mendelian dihybrid ratio or epistatic ratios. This hypothesis was tested for 17 molecules in three tissues; nerve, skin and plasma and were confirmed to interact in 9:7, 9:3:4, 12:3:1, 13:3, 15:1 epistatic proportions. These findings suggest that there could be a significant role of networking of molecules in defined epistatic proportions and could be important in pathophysiology of peripheral nerve.

Xenopus tropicalis offers the potential for genetic analysis in an amphibian. In order to take advantage of this potential, we have been inbreeding strains of frogs for future mutagenesis. While inbreeding a population of Nigerian frogs, we identified three mutations in the genetic background of this strain. These mutations are all recessive embryonic lethals. We show that multigenerational mutant analysis is feasible and demonstrate that mutations can be identified, propagated, and readily characterized using hybrid, dihybrid, and even trihybrid crosses. In addition, we are optimizing conditions to raise frogs rapidly and present our protocols for X. tropicalis husbandry. We find that males mature faster than females (currently 4 versus 6 months to sexual maturity). Here we document our progress in developing X. tropicalis as a genetic model organism and demonstrate the utility of the frog to study the genetics of early vertebrate development.

Two new body color mutations are described in both a wild-type, usually green (GG), and a red strain (gg) of Canthon cyanellus cyanellus LeConte, a scarab from the tropical forest in Los Tuxtlas, Veracruz, Mexico. One mutation changed the testaceous (TT) color of mouthparts, antennae, palpi, and tarsi in the red and wild-type strains to a piceous (tt) color, retaining the red and green body color, respectively. Specimens with this mutation were reared in laboratory to determine whether the genetic behavior of the character was controlled by a single autosomal recessive allele. Specimens of the new strain, recessive homozygous (gg/tt), were crossed with wild-type beetles. The phenotype of F2 offspring from these crosses segregated in a ratio of 9:3:3:1 according to a dihybrid cross. Specimens of the GG/TT genotype were intercrossed, and in F1 a second mutation changed the brown (BB) eye color to nonmelanin (bb), retaining the green body color. Crosses were made between beetles with this character ...

Grain number per unit area is an effective component of grain yield in bread wheat. Water-stress induced apical sterility (tip sterility) reduces the number of grains and, consequently, the grain yield in semi-arid regions with a shortage of available water during the pre-anthesis period. Crosses between apical sterile and apical fertile varieties and selection lines were made and F1, BC1, and F2 populations were subjected to moderate water-stress to study the inheritance of this character. The F2 and BC1 plants were qualitatively categorised into two phenotypes and tested for monohybrid and dihybrid segregation hypotheses. All the spikes of F1 plants obtained from crosses between apical fertile and apical sterile varieties were fully fertile indicating apical fertility is dominant to apical sterility. The F2 segregation Results from crosses between apical fertile lines and Y82187 suggested two complementary dominant genes segregating independently were involved in tolerance to water-stress induced apical sterility. In other words, two dominant genes determine apical fertility in these crosses and if one of these loci is homozygous, recessive waterstress will induce apical sterility. One F2 population segregated for both apical sterility and vernalisation response. Semi-winter plants had more sterile spikelets and the result of chi-square test confirmed monhybrid segregation for vernalisation response.

With 1 table ABSTRACT: In this study, single crosses involving four CMS lines and three known fertility restorers were studied to determine the genetics of fertility restoration in pigeonpea (Cajanus cajan L. Millsp.). The F1 plants of all the four hybrids were selfed to produce F2 seed and simultaneously crossed to their corresponding A lines to produce BC1F1 seeds during 2007. The parents, F1, F2 and BC1F1 populations were planted in 2008 rainy season at the Marathwada Krishi Vidyapeeth, Parbhani, India. The interaction of dominant nuclear genes of ICP 2766 with ICPA 2092 produced 100% fertile F1 plant and showed complete dominance for fertility restoration. The restorer ICP 2766 when crossed with ICPA 2092 showed monogenic inheritance (3 : 1), while ICP 2766 crossed with ICPA 2043 revealed digenic inheritance (15 : 1) of fertility restoration. In a cross between ICP 2766 and ICPA 2043, dominant gene of fertility restoration at either of two loci masked the expression of male‐sterile recessive alleles at two loci in such a way that it modified normal dihybrid ratio into 15 : 1 ratio and produced duplicate gene interaction.

VARIATIONS in the color of corn kernels (Zea mays L.) have attracted geneticists since the early 1900s when studies on the inheritance patterns of kernel color helped validate classical genetics. Even now, research scientists investigate the molecular genetics of these characteristics, and students in introductory biology and genetics courses learn more about monohybrid and dihybrid crosses by studying the inheritance of kernel colors. The reasons for introducing corn genetics in the classroom are obvious—a single ear holds a large number of progeny and a variety of ears are available that represent basic inheritance patterns, such as the monohybrid cross (3:1), the dihybrid cross (9:3:3:1), and more complex genetic patterns illustrating gene interactions (12:3:1; 9:3:4, 13:3; 9:7, etc.). In addition, these ears are obtained readily from several biological supply houses and are relatively inexpensive, especially since students can use them for several years. Students usually confirm different phenotypic ratios of the F2 generation by first counting kernels, then performing chi-square analyses to test their data. However, their experience can be enriched by introducing explanations about the nature of each gene and its mutations, the related metabolic pathways, and their locations within the kernel. I have included information in this review that would be appropriate at different levels—from high school biology to introductory genetics at the college level. The purpose is the same. By exploring these areas, students more fully understand how these simple phenotypic ratios and variations are derived.

Selective breeding of Long-Evans rats for good and poor avoidance learning in a two-way shuttle box resulted in the Syracuse strains that differ markedly in the selected phenotypes. These phenotypes have many associated traits, five of which are studied here: emotionality (open-field defecation), Pavlovian fear conditioning (CER suppression), passive avoidance training (punishment), size (weight) of the adrenal glands and adrenal concentration of corticosterone. Specifically, animals of the low-avoidance strain are more emotional, show greater fear conditioning, exhibit faster passive avoidance learning, and have larger adrenal glands in which adrenal corticosterone levels are lower than those of the high-avoidance strain. A reciprocal dihybrid cross of the two strains produced F1 hybrids, which were used to produce the segregating second filial and high and low backcross generations from which animals displaying the extreme high- and low-avoidance phenotypes were selected for study of the associated traits. Measurement of the five traits in these high and low phenotypic animals indicated that all five remain significantly associated with the avoidance phenotypes, in the expected direction, and comparably in all three segregating generations. The results indicate that the hypothesis of a major gene controlling avoidance learning must be rejected and that the few (2-3) genetic units thought to be involved may be closely linked to those that mediate these five associated characters, or express all five pleiotropically.

Typical dihybrid Mendelian phenotypic ratios are 9:3:3:1 for AaBb X Aabb crosses. If the genes involved interact in their effects on the phenotype, altered phenotypic ratios such as 9:3:4, 9:7, 12:3:1 and others may result as a consequence of gene interactions called epistasis. The colors of onions found in grocery stores are a relevant example. When red onions (AABB) are crossed with white onions (aabb), the dihybrid offspring are red (AaBb), and the offspring of a mating between dihybrids (AaBb x AaBb) are 9 red: 3 yellow: 4 white onions. Students learning genetics often have difficulty grasping the concept of gene interaction well enough for them to be comfortable predicting the outcomes of crosses or interpreting the genetic bases of such outcomes. A method I use successfully to teach gene interaction is to give examples where the genes involved affect various steps in biochemical pathways. A biochemical (metabolic) pathway is a sequential series of chemical reactions by which substrates are altered step-by-step to produce the desired end product. Once students grasp the notion that genes can interact because they control different steps within biochemical pathways, the reason why phenotypic ratios appear to be non-Mendelian becomes more obvious and comprehensible.

Drosophila melanogaster is a commonly utilized organism for testing hypotheses about inheritance of traits. There is a wide variety of mutants of Drosophila that demonstrate effectively both dominant and recessive traits, as well as autosomal and X-linked inheritance (Flagg, 2005; Winchester & Wejksnora, 1996). Students in both high school and university labs study the genetics of inheritance by analyzing offspring of appropriate Drosophila crosses to determine inheritance patterns, including gene linkage. However, most genetics investigations with Drosophila analyze offspring patterns of the F2 generation of dihybrid crosses to determine that genes are linked but do not calculate the map units between the linked genes (College Board, 2001; Mertens & Hammersmith, 2007; Scott, 2001). Calculating map units between linked genes is most straightforward when testcross data is used (Brooker, 2005; Russell, 2006). However, setting up a testcross is not trivial. Constructing a testcross in Drosophila requires obtaining an F1 virgin female fly to mate with a homozygous recessive male fly in order to produce the subsequent generation for analysis of traits. In a teaching lab setting in which there are severe constraints on lab time, students have great difficulty in obtaining virgin F1 females to set up the testcross to generate data for mapping. This article describes how to use F2 data generated from an F1 sibmate cross to determine map distances in linked genes. Lab Method & Data Analysis Drosophila crosses with virgin parentals are either set up by the instructor (Flagg, 2005) or are ordered from a commercial supplier (Carolina Biological Supply, Burlington, NC or Ward's Natural Science, Rochester, NY). These crosses can be set up either as a coupling cross or as a repulsion cross. The coupling cross is performed by crossing a wild-type fly to one that has both mutant phenotypes in the homozygous form. An example would be crossing a wild type fly to one with sepia eyes and ebony body. The repulsion cross is performed by crossing one homozygous mutant with another. An example of this would be crossing a fly with sepia eyes to one with an ebony body. After one week, the parentals are removed and the larvae are allowed to hatch into the F1 generation. Students analyze the F1 generation of the appropriate Drosophila cross to determine which traits are dominant and which are recessive. The F1 generation of this Drosophila cross is then allowed to sibmate in a new vial of Drosophila media. After one week, the F1 generation is removed from the vial and the larvae are allowed to remain. After an additional week, the F2 generation is removed, anesthetized or immobilized, and sorted according to sex and phenotype (College Board, 2001; Flagg, 2005; Mertens & Hammersmith, 2007; Scott, 2001; Winchester & Wejksnora, 1996). Once data are obtained, students use chi-square analysis (College Board, 2001; Brooker, 2005; Russell, 2006) to determine if the genes are linked or independently assorting. They hypothesize that the F2 generation should produce a 9:3:3:1 ratio and use chi-square analysis to determine if the offspring fit the hypothesized ratio (College Board, 2001; Brooker, 2005; Russell, 2006). To make this exercise more investigative, students can develop hypotheses based upon their knowledge about the chromosomal theory of inheritance, gene linkage, and crossing over (Brooker, 2005) before they count the F2 generation. Once students understand coupling and repulsion crosses, they can predict the outcomes of the F2 generations in the coupling and repulsion crosses for linked genes, if no crossing over has occurred. Students should be able to determine that in a coupling cross, the F2 should produce no offspring demonstrating a single recessive trait unless crossing over occurred. Further investigation should allow the students to hypothesize that in the repulsion cross, the double recessive offspring should not be seen in the F2 unless recombination has occurred. …

Genes act independently to influence organismal traits. Although Gregor Mendel studied some “dihybrid” crosses (those involving two genes) in his experiments on pea plants, the particular loci that he monitored proved to be independent in their effects on various of the plants’ phenotypes. Thus, the only genetic interactions that he observed involved intra-locus effects, as for example when one allele was dominant or recessive to its counterpart at the same diploid gene.

Gregor Mendel used his knowledge of plant varieties and statistics to solve the problem of how traits seemed to disappear in a hybrid generation. He deduced that genetic information is transmitted in units that separate at each generation. His two ‘laws’ are applicable to genes carried on different chromosomes. His laws are still important today in predicting inheritance of DNA sequences.

Phosphorus deficiency (PD) is a limiting factor in rice farming and hence PD tolerant varieties are essential. The PD tolerant quantitative trait loci (QTL) have been identified using the rice landraces Kasalath and Nipponbare. However, PD tolerant Sri Lankan rice landraces or varieties have not been used for QTL mapping. It is important to study the genetics of the PD tolerance associated traits of the locally grown rice genotypes before mapping QTL. Thus, aim of this study was to unravel the genetics of PD tolerant associated traits in segregating progenies generated by crossing PD tolerant and sensitive rice genotypes. Four F 2 progenies (H-4 × Bg 352, Suduheenati × Bg 352, Mas × Bg 352 and Suduheenati × Bg 357) had been created by crossing PD sensitive genotype Bg 352 with PD tolerant genotypes H-4, Suduheenati and Mas and PD sensitive genotype Bg 357 with PD tolerant genotype Suduheenati, respectively. The F 2 seeds from each cross along with the parents were grown in a greenhouse using a P deficient soil. The growth and quantitative colour parameters were measured at flowering stage. The normality, broad sense heritability and heterosis were calculated for each trait. Goodness of fit tests were conducted for colour metrics considering the common epistatic dihybrid ratios. The growth parameters were normally distributed with higher heritability indicating a potential basis for QTL mapping. The colour metrics were not normally distributed and fitting into the epistatic ratios 9:3:4, 9:6:1, 10:3:3 or 12:3:1 implying that they should be controlled by major genes. All the studied traits showed higher heritability estimates. According to this information, it would be logical to map QTL for growth parameters and colour variation occurred due to PD.

Successful application of genetic transformation technique, especially in developing rice variety resistant to brown plant hopper and stem borer, will depend on transgene being expressed and the gene inherited in a stable and predictable manner. This study aimed to analyse transgene segregation pattern of the progenies and the crosses of transgenic rice cv. Rojolele harboring cry1Ab and gna genes. The third generation (T2) of fivetransgenic Rojolele events containing gna and/or cry1Ab were evaluated for two generations to identify the homozygous lines and to study their inheritance. The homozygous lines were selected based on the result of PCR technique. The segregation patterns of gna and cry1Ab were studied in eight F2 populations derived from Rojolele x transgenic Rojolele homozygous for cry1Ab and or gna and their reciprocal crosses. Data resulted from PCR of F2 population were analysed using a Chi Square test. The study obtained six homozygous lines for gna, namely A22- 1-32, A22-1-37, C72-1-9, F11-1-48, K21-1-39, K21-1-48, and two homozygous lines for cry1Ab, namely K21-1-39 and K21- 1-48. Both cry1Ab and gna transgenes had been inherited through selfing and crossing with their wild type as indicated from the F1 containing gna and cry1Ab as many as 48.4% and 47.4%, respectively. In six of the eight crosses, gna was inherited in a 3:1 ratio consistent with Mendelian inheritance of a single dominant locus, while in the remaining two crosses, gna was segregated in a 1:1 ratio. The presence of cry1Ab in F2 populations also showed a 3:1 segregation ratio in all crosses. In the F2 population derived from F1 plant containing cry1Ab and gna, both transgenes segregated in a 9:3:3:1 dihybrid segregation ratio. This study will add to the diversity of genetic sources for insect resistance and allow further use of these transgenic lines for pyramiding resistance to brown plant hopper and stem borer or separately in rice breeding programs whenever the efficacy tests and biosafety requirements have been completed.

The physical differences between major non-African ethnic, groups can be explained as admixture of migrating African modernHomo sapiens with existing archaicHomo populations. Evidence from mitochondrial DNA claiming no admixture is dismissed as there is no confidence in claimed phylogenies. Racial characteristics can be explained by linking present day non-African humans with sympatric archaic populations. Neanderthals are linked with Caucasians, the Solo population with Australian Aborigines and ‘Peking Man’ with modern Mongoloids. Fossil, geographic and anthropometric evidence for dihybrid origins are considered. As a result, Asiatic Negritos are hypothesized to be remnant groups of ‘morphologically pure’ migrating modern Africans. It is suggested that paleoanthropologists attempting to reconstruct human origins should consider the dihybrid theory as a plausible alternative to the irreconcilable ‘complete replacement’ and ‘multiregional’ theories.

Many of the same features of the yeast Saccharomyces cerevisiae that have made it so useful as a genetics and molecular biology research organism make it equally useful as a teaching organism. Furthermore, the fact that it is a modern research organism makes it all the more exciting to students and teachers. The unique characteristic of yeast as a unicellular, eukaryotic organism with a complete sexual life cycle is ideal for teaching. A simple monohybrid cross to explore dominance and recessiveness, a dihybrid cross to demonstrate independent assortment, pigmented adenine auxotrophs for investigating the fundamentals of gene action, and easily measured responses to ultraviolet radiation provide an array of appropriate laboratory tools that put real science in the hands of students and teachers. Direct collaborations between scientists and science teachers bring together complementing knowledge and experience, providing an effective and efficient way to adapt and simplify techniques and procedures to accommodate time and money constraints. Collaborations quickly identify technical and theoretical problems that must be solved for implementation in classrooms. They also provide a continuing stimulus to teachers and students to participate in the research process.

A recessive allele that causes semidwarf stature in the sweet pea, Lathyrus odoratus L., was identified and designated lb. The recessive allele for dwarf habit, l, is epistatic to the Lb-lb pair of alleles in the sense that a clear dihybrid F 2 segregation ratio of 9 tall (L-Lb-): 3 semidwarf (L-lblb): 4 dwarf (ll−) was obtained

Mendel's second law of heredity, also known as the law of independent assortment, states, (1) that during meiosis genes located on nonhomologous chromosomes assort independently of one another, or (2) that during meiosis the two homologs of one pair segregate independently of all other homologous pairs (Raven & Johnson 1996). It has been my experience as a college professor that independent assortment is one of the most difficult concepts for students to comprehend. In part, this difficulty arises because in high school, independent assortment is usually introduced during a discussion involving dihybrid crosses (e.g. Definition 1). However, because genes are located on chromosomes, it makes more sense to introduce the concept of independent assortment during a discussion of meiosis (e.g. Definition 2); if students can understand the movement of chromosomes, then they should more easily understand the movement of genes. The concept of independent assortment has been addressed in several recent issues of The American Biology Teacher (Atkins & Roderick 1991; Burns 1996; Levy & Benner 1995). Students' understanding of a difficult concept is greatly enhanced if the concept is presented concretely, and if they are left with a pleasurable reminder of the demonstration (Arnheim 1991, 1993; Rakes 1996; Relan 1991; Roth 1993; Szabo et al. 1981). Presented here is a quick, inexpensive method to demonstrate independent assortment concretely. It is intended to enhance concept attainment, not as a laboratory exercise. The procedure can be used to illustrate independent assortment either during meiosis or during a dihybrid cross.

Glume cultures of monogenic recessive mutants PGTSLS1 (Plant Genetics triticale selection large spike 1) and PGTSLG2 (Plant Genetics triticale selection long grain 2) were employed along with their parent PGTS control (Plant Genetics triticale selection control) and their F1 and F2 progenies, to determine the genetic basis of plant regeneration in hexaploid triticale. The mutant PGTSLS1 exhibited greater efficiency of plant regeneration (22.4%) followed by PGTS control (7.6%) and PGTSLG2 did not exhibit any regeneration. All the three F1's exhibited plant regeneration frequency on par with that of control (6.9–7.3%), suggesting dominant nature of control genotype over the isogenic mutants. The F2 results suggested that genetic control over the high frequency regeneration of PGTSLS1 was monogenic recessive in nature, and genetic control over the recalcitrant nature of PGTSLG2 also was monogenic recessive. The F2 of the cross PGTSLS1 × PGTSLG2 segregated into four classes. Of the 114 F2 plants, 19 showed no regeneration, 70 of them exhibited 6–8% regeneration, 20 of them 19–24% regeneration, and 5 of them exhibited highest frequency regeneration (57–60%). These observations suggest dihybrid segregation for regeneration. The highest frequency of plant regeneration (57–60%) exhibited by 5 F2 plants may be due to the interaction of non-allelic genes in recessive condition. These results clearly demonstrate the association of at least two genes with plant regeneration in hexaploid triticale.

Six transgenic tobacco lines, each homozygous for the β-glucuronidase (GUS) gene at a different locus, and wild type were selfed and intercrossed to evaluate GUS activity in all possible hemizygous, homozygous and dihybrid combinations of GUS alleles. The transgenic lines are characterized by their GUS activity (two low, three intermediate, one high), T-DNA complexity (four single-copy, two more complex single-locus) and the presence of the chicken lysozyme matrix-associated region (MAR) around the full T-DNA (two lines). Gene action and interaction was analyzed by weighted linear regression with parameters for additivity, dominance and epistasis. The analysis showed that each of the four single-copy lines acted fully additively. In contrast, the two complex single-locus lines showed classical single-locus overdominance and were epistatic dominant over all other GUS alleles. The latter is manifested in severe suppression of GUS activity in dihybrid lines, irrespective of the presence of MAR elements around the GUS gene. Such elements apparently do not protect against epistatic dominance. The quantitative data suggested that the epistatic dominance and overdominance are based on the same molecular mechanism. Our approach of a genetic analysis of quantitative variation in well-characterized transgenic lines provides a powerful tool to gain insight into complex plant traits.

Population genetics is a branch of biology which studies about the gene composition from population and the change of the gene composition is effect from some factors. One of them is lethal gene factor. The change of gene composition will influence the genotype probabilities in the population. In this paper discussed about determining the genotype for the probability of the n-th offspring genotypes in dihybrid mating by observing linkage between the two loci. The mating occurred randomly and without concern ethics in mating. This research was done by making mathematics model to determine allele pair, using difference equation, then from this model will be determined genotypes probability. The result show that the mating happened normally had the same genotype probability of each generation, meanwhile in abnormal mating, the genotype probability whose had lethal gene would decrease and the genotype probability whose did not have lethal gene would increase in each generation.Keywords : Difference equation, dihybrid mating, lethal gene, population genetics, probability

Mating of two parental varieties always leads to the production of genotypic admixture of both the parental traits in F1 and on selfing the progeny exhibits the phenotypic segregation in a definite proportion in F2. Mendel described it as “Law of Independent Assortment”. It is general belief that coffee varieties do not follow the Mendel’s ratios of segregation. Keeping in view the above findings and beliefs, a study was undertaken during 2008-2011 to observe the segregation pattern in the F2 population of C. arabica cv. ‘Cauvery’ x (C. congensis x C. canephora var. robusta) established at Coffee Research Sub Station, Chettalli, Kodagu District, Karnataka, India in the year 2002. The results of the study revealed that coffee cultivars of commercial importance possessed two types of genetic traits known as dependent and independent characters. The dependent characters showed assortment of characters along with closely related characters and expressed varying degrees of expression. Therefore, the frequency of the occurrence of such phenotypic traits did not considerably match with the expected frequency of the same traits at high probability level and it matched at low probability. The genetic behavior of independent traits exhibited genetic segregation in accordance with the Mendel’s law of independent assortment showing goodness of fit to the dihybrid ratio of 9:3:3:1 with high level of statistical confidence (P≥0.50 up to 0.95). It was observed that the genes regulating the dwarfing effect for coffee bush, thin stem and primary girth, low number of primary branches and reduced length of primary branches were dominant over tall type bush, thick main stem and primary shoot as well as higher number and length of primary shoots.

Mendel, the father of genetics took the first steps in defining "contrasting characters, genotypes in F1 and F2… and setting different laws". The genotypes of F2 is dependent on the type of its parents genotype and it follows certain roles. Purpose of this paper is to analyze the second generation genotypes of monohybrid and a dihybrid with a mathematical structure. We use the concept of Hv-semigroup structure in the F2-genotypes with cross operation and prove that this is an Hv-semigroup. We determine the kinds of number of the Hv-subsemigroups of F2-genotypes.

Mexican Americans are a numerous and fast growing ethnic population in the United States. Yet little is known about their genetic structure. Since they are a hybrid, it is of interest to identify their parental populations and to estimate the relative contributions of these groups. This information is relevant to historical, biomedical, and evolutionary concerns. New genetic typings on 730 Arizona Mexican Americans for the HLA-A, HLA-B, ABO, Rh, MNSs, Duffy, Kidd, and Kell loci are presented here and they are used to estimate ancestral contributions. We considered both a dihybrid model with Amerindians and Spaniards as proposed ancestors, and a trihybrid model with Amerindians, Spaniards, and Africans as proposed ancestors. A modified weighted least squares method that allows for linkage disequilibrium was used to estimate ancestral contributions for each model. The following admixture estimates were obtained: Amerindian, 0.29 +/- 0.04; Spaniard, 0.68 +/- 0.05; and African, 0.03 +/- 0.02. The interpretation of these results with respect to Amerindian and Spanish ancestry is straightforward. African ancestry is strongly supported by the presence of a marker of African descent, Fy, despite the fact that the standard error of the estimate is as large as the estimated admixture proportion. An evaluation of the sensitivity of these results to a number of variables is presented: 1) our choices of ancestral allele frequencies, 2) the possibility of selection at HLA and the blood groups, and 3) genetic drift in Mexican Americans.

Complementation tests revealed that albinism in four laboratory strains of Physa (Physella) heterostropha pomilia resulted from two recessive, nonallelic genes. F2 dihybrid progeny displayed the 9:7 ratio classically associated with reciprocal recessive epistasis between unlinked loci. This offers a contrast to the situation in the better known planorbid snails and provides a valuable tool for the study of reproductive biology in these facultatively self-fertilizing hermaphrodites.

Ten clones ofSolanum stoloniferum Schlechted (2n — 4x — 48) were selected from seedling populations that were produced by self-pollinating five introductions from the Commonwealth Potato Collection. These clones were used to produce S1, F1, F2, and testcross populations. Clones and their progeny were scored for anthocyanins and flavonol glycosides in their corollas, stems, and leaves. Thin-layer chromatography (TLC) was used to separate and identify polyphenol compounds. No segregation for eight traits was observed within S1 and F1 families. Segregation was observed in F2 and testcross populations for anthocyanins (derivatives of delphinidin and cyanidin, inhibited when the geneF is homozygous recessive); and flavonol glycosides (Q4 = quercetin 3-glucosyl-rhamnosylglucoside, controlled by the geneG1; and L1 = luteolin 7-glucoside, controlled by the geneL1) extracted from corollas. Observed ratios fitted ratios expected for disomic inheritance, differed from expected tetrasomic ratios, and provided additional evidence that the parental clones are homozygous. GenesF, G1, andL1 were genetically independent in dihybrid and trihybrid F2 crosses.

A greenish-yellow mutant was obtained after treatment of seeds of Nicotiana tabacum L. var. Xanthi n.c. with ethyl methanesulfonate (EMS). Two genetically independent mutations ( a 1 and a 2 ) were isolated. The first mutation ( a 1 ) antagonizes the function of its partially dominant a 1 + allele. The second mutation ( a 2 ) is amorphous but strongly interacts with a 1 . Among the nine possible genotypes at the two loci, five varied in somatic cells. The heterozygous state a 1 + / a 1 strongly increased the frequency of both spontaneous and induced variations. However, two homozygotes also showed variations. Variants were isolated from induced and spontaneous non-reciprocal and reciprocal variations within paliside tissues by bud induction in vitro . They were genetically tested. In this first paper, only non-reciprocal variations are reported. Green variants from the greenish-yellow ( J 1 ) dihybrid a 1 + / a 1 a 2 + / a 2 clone had two genotypes: the first was due to true reversions of a 1 to a 1 + , whereas the second was due to amorphous a 1 0 mutations from a 1 . These a 1 0 mutations may well be deletions. The lightest yellow variants from J 1 were due to mutations either from a 1 + into a 1 or from a 2 + into a 2 . Deletions at the a 1 + − a 1 locus led to either yellow variations when a 1 + was lost, or to false reversions when the antagonistic allele a 1 was lost. Amorphous alleles at the a 1 + − a 1 locus were also isolated from tissues other than J + . They gave zygotic lethality ( s ) that probably varied with the size of the deletions. Thus, true reversions and deletions at the a 1 + − a 1 locus could be distinguished from one another by progeny tests. Other variants showed higher frequencies of spontaneous variations (instability). Somatic changes observed in these unstable systems were due to modifications at the marker loci. The genetic nature of this instability is not yet known. There is strong evidence that the genetic events involved in these non-reciprocal variations were deletions, conversions and point mutations. True reversions from a 1 into a 1 + and new mutations from a 1 + into a 1 were obtained only from a 1 + / a 1 . It was therefore supposed that the changes observed took place only in heterozygotes, and the conversion hypothesis was made. Attempts are being made to prove that conversions do exist in higher plants, and to find out if this process, as deletions, is induced by radiation.

The pattern of inheritance of isozyme alleles was examined in the F2 progeny of a sexual cross between two different physiologic races of the wheat stem rust pathogen, Puccinia graminis Pers. f. sp. tritici Eriks. &Henn. Segregation occurred at five isozyme loci (Got, Lap, Nadhd, Pgi-2 and Pgm-1). In all of these, the observed number of F2 progeny of each of the three possible isozyme phenotypes did not differ significantly from a simple 1:2:1 ratio. Joint dihybrid segregation indicated that three of the loci formed a single linkage group: Lap–Nadhd–Pgi-2.Key words: linkage, segregation.

A genetics problem practice program and tutor on microcomputer was used by 135 undergraduate education majors enrolled in an introductory biology course at Purdue University. The program presented four genetics problems, two monohybrid and two dihybrid, and required the users to predict the number and type of each class of offspring. Student responses were recorded on diskette and analyzed for evidence of misconceptions and difficulties in the genetics problem-solving process. Three main areas of difficulty were identified: difficulties with computational skills, difficulties in the determination of gametes, and inappropriate application of previous learning to new problem situations.

A model is presented which allows estimation of linkage from dihybrid F2 populations with distorted single gene segregation by applying the maximum-likelihood method. For different selection processes operating on one locus at either the gametic or the zygotic level, it can be demonstrated that, if the deficit is previously taken into account, testing for free recombination can be carried out without prior knowledge of the causes of this deficit. In the presence of linkage, the expected frequencies of two phenotypic classes depend on whether gametic or zygotic selection is operating. The remaining two classes can be utilized for the estimation of linkage as their frequency ratio is independent of these selection types. The application of this procedure to situations with coupling, incomplete penetrance, gametic and zygotic selection is discussed.