Exam 4: Extensions of Mendelian Genetics

A cross was made between homozygous wild- type female Drosophila and yellow- bodied male Drosophila.All of the resulting offspring were phenotypically wild type.Offspring of the F₂ generation had the following phenotypes: Based on this information,how is the yellow allele inherited?

In a mating between individuals with the genotypes I^Ai × ii,what percentage of the offspring are expected to have the O blood type?

Assume that a dihybrid F₂ ratio,resulting from epistasis,was 15:1.If a double heterozygote was crossed with the fully recessive type,what phenotypic ratio is expected among the offspring?

A particular cross gives a modified dihybrid ratio of 9:7.What phenotypic ratio would you expect in a testcross of the fully heterozygous F₁ crossed with the fully recessive type?

The trait for medium- sized leaves in iris is determined by the genetic condition PP'.Plants with large leaves are PP,whereas plants with small leaves are P'P'.The trait for red flowers is controlled by the genes RR,pink by RR ',and white by R'R'.A cross is made between two plants each with medium- sized leaves and pink flowers.If they produce 320 seedlings,what would be the expected phenotypes,and in what numbers would they be expected? Assume no linkage.

Achondroplasia is a form of human dwarfism.If two individuals with achondroplasia have children with the following ratio,2 dwarf to 1 wild type,what is the means of inheritance of this phenotype?

Because of the mechanism of sex determination,males of many species can be neither homozygous nor heterozygous.Such males are said to be ________ .

In mice,there is a set of multiple alleles of a gene for coat color.Four of those alleles are as follows: C = full color wild type C^ch = chinchilla C^d = dilution C = albino Given that the gene locus is not sex- linked and that each allele is dominant to those lower in the list,give the ph ratios expected from the following cross. Chinchilla heterozygous for albino)× albino

The genes for zeste eyes and forked bristles are located on the X chromosome in Drosophila melanogaster.Both genes are recessive.A cross is made between a zeste- eyed female and a forked- bristled male.If 200 offspring from this cross were obtained,what is the expected offspring's phenotype and sex?

Two forms of hemophilia are determined by genes on the X chromosome in humans.Assume that a phenotypically normal woman whose father had hemophilia is married to a normal man.What is the probability that their first son will have hemophilia?

What is the blood type of individuals who cannot add the terminal sugar to the H substance?

What would be a typical phenotypic monohybrid ratio in which a lethal allele is involved?

Many of the color varieties of summer squash are determined by several interacting loci: AA or Aa gives white,aaBB or aaBb gives yellow,and aabb produces green.Crosses among heterozygotes give a 12:3:1 ratio.What type of gene interaction would account for these results?

Assume that a dihybrid cross is made in which the genes' loci are autosomal,independently assorting,and incompletely dominant.How many different phenotypes are expected in the offspring?

The trait of medium- sized leaves in iris is determined by the genetic condition PP'.Plants with large leaves are PP,whereas plants with small leaves are P'P'.A cross is made between two plants each with medium- sized leaves.If they produce 80 seedlings,what would be the expected phenotypes,and in what numbers would they be expected?

Which of the following is true?

In a mating between individuals with the genotypes I^AI^B × ii,what percentage of the offspring are expected to have the O blood type?

What term is used to express the idea that several genes exert influence over the same characteristic?

Assume that a mutation occurs in the gene responsible for the production of hexosaminidase A,such that only about 50% of the enzyme activity is found in the heterozygote compared with a homozygous normal individual.If heterozygotes are phenotypically normal,we would say that the mutant allele is ________to its normal allele.

Which mutations are generally dominant since one copy in a diploid organism is sufficient to alter the normal phenotype?