Exam 4: Extensions of Mendelian Genetics

Penetrance specifically refers to the expression of lethal genes in heterozygotes.

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

One result of X-linkage is a crisscross pattern of inheritance in which sons express recessive genes of their fathers and daughters express recessive genes of their mothers.

Provide an example of sex-influenced inheritance.

Typically,when one wishes to represent a gene,the symbol used is _________.

The white-eye gene in Drosophila is recessive and sex-linked.Assume that a white-eyed female is mated to a wild-type male.What would be the phenotypes of the offspring?

In the mouse,gene A allows pigmentation to be deposited in the individual coat hairs; its allele a prevents such deposition of pigment,resulting in an albino.Gene B gives agouti (wild-type fur); its allele b gives black fur. a) Diagram the cross between a doubly heterozygous agouti mouse mated with a doubly homozygous recessive white mouse. b) What would be the expected phenotypic ratio in the progeny?

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

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

Sex-limited inheritance is the same as sex-linked inheritance.

Hemizygosity is the term one uses to describe the state of a gene that has no allele on the opposing chromosome.

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

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. a) If 200 offspring from this cross were obtained,present the expected number,sex,genotype,and phenotype in each class of the F₁. b) If the F₁ offspring were crossed to produce 800 flies of an F₂ generation,present the expected number,sex,and phenotype in each class.Assume no crossing over.

Genomic imprinting occurs when one allele converts another.

Which types of ratios are likely to occur in crosses (F₂)when one is dealing with two interacting,epistatic gene pairs?

Comb shape in chickens represents one of the classic examples of gene interaction.Two gene pairs interact to influence the shape of the comb.The genes for rose comb (R)and pea comb (P)together produce walnut comb.The fully homozygous recessive condition (rrpp)produces the single comb.Assume that a rose-comb chicken is crossed with a walnut-comb chicken and the following offspring are produced: 17 walnut,16 rose,7 pea,6 single. a) What are the probable genotypes of the parents? b) Give the genotypes of each of the offspring classes.

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 typical epistatic ratio is 9:3:4.

A situation in which there are more than two alternative forms of a given gene would be called ________.

Pattern baldness is determined by a single autosomal gene pair.When females are homozygous for this gene pair,can they show pattern baldness?