Exam 9: Inheritance

When two genes are linked, most of the phenotypes of the parental traits will be inherited together. For example, eye colour and bristle form in the vinegar fly, Drosophila, are linked. The alleles for white eyes and crooked bristles occur on one chromosome in a fly while the alleles for red eyes and straight bristles occur together on another chromosome. Gametes produced by the fly that contain a chromosome with both the white-eye allele and the straight-bristle allele are referred to as

The principle of independent segregation results in

The frequency of recombination was used to determine the map order of 4 genes, A-D. The distance from A-B was 4 cM; A-C was 30 cM; A-D was 20 cM; B-C was 26 cM; C-D was 40. What is the correct order of the genes?

In tomato plants, a gene controlling fruit shape has 2 alleles: O (round) and o (oval). A gene controlling inflorescence (position of the flowers) has two alleles: S (simple) and s (compound). The map distance between the two genes is 22 cM. A pure-breeding plant with oval fruit and compound inflorescence is crossed with a pure-breeding plant with round fruit and simple inflorescence. The F₁ have round fruit and simple inflorescence. The F₁ are then crossed to plants with oval fruit and compound inflorescence and 100 offspring are produced. How many of the offspring would you expect to have oval fruit and simple inflorescence?

The colour of wheat seeds is controlled by two genes. The alleles (R₁ and r₁) of one gene assort independently to the alleles (R₂ and r₂) of the other gene. R₁ and R₂ produce a red pigment while r₁ and r₂ do not produce any pigment. The effect of the alleles is additive so that R₁/R₁; R₂/R₂ give dark red colour while r₁/r₁; r₂/r₂ produces white. A plant with R₁/r₁; R₂/r₂ has intermediate red colour. If the following cross was set up: R₁/r₁; R₂/r₂ x R₁/R₁; R₂/R₂

The colour of wheat seeds is controlled by two genes. The alleles (R₁ and r₁) of one gene assort independently to the alleles (R₂ and r₂) of the other gene. R₁ and R₂ produce a red pigment while r₁ and r₂ do not produce any pigment. The effect of the alleles is additive so that R₁/R₁; R₂/R₂ give dark red colour while r₁/r₁; r₂/r₂ produces white. A plant with R₁/r₁; R₂/r₂ has intermediate red colour. A plant heterozygous at both gene loci was allowed to self-fertilise. What proportion of offspring would be expected to have a colour similar to the parent?

A farmer has a new plant that has not been previously domesticated and wants to start breeding it to produce larger fruit. As fruit size is a polygenic trait, what approach should the farmer take in attempting to quickly and efficiently increase the fruit size?

One of the main reasons that genes assort independently of each other is

In a organism heterozgyous for a particular allele

An Honours student is working on a project to determine the distance between two loci. She performs fifty crosses and observes 8 recombination events between the two loci. What is the distance between the two loci?

Which of the following crosses is a BACKCROSS?

A gene controlling flower colour also controls the colour of the stem and seed coat. This phenomenon is known as

Peas are an appropriate choice for studies of genetic inheritance because

Two alleles control a trait for pathogenicity in a species of bacteria. Those homozygous for allele A cause a virulent disease upon infection of a host, whereas those homozygous for allele B cause no symptoms whatsoever. Bacteria carrying both alleles cause a mild disease upon infection of a host. No other differences in phenotype were observed. If allele A produces a dose-responsive toxin and allele B produces no toxin, what kind of trait would this be?

Autosomes are

Stem length, seed shape and flower colour in pea plants are determined by three independently assorting genes. Each trait has a dominant and a recessive phenotype. If a plant that is heterozygous for the three traits is allowed to self-fertilise, you would expect 3/8 of the offspring to be

A male patient of Mediterranean origin is rushed into the trauma centre of a major hospital and requires an immediate blood transfusion. The patient's medical history is unknown and there is insufficient time to perform a blood typing analysis. Which blood type should the patient be given and why?

Variation in phenotypic expression involves both expressivity and penetrance. Penetrance is

The presence or absence of hair on the mid-digital region of a finger is determined by a single autosomal gene. The presence of hair is dominant to the absence of hair. In the pedigree below, shading represents the presence of mid-digital hair. If the parents have a 5th child, what is the probability that it will be female and have mid-digital hair?

Which of the following statements about sex-linked traits in humans is true?