Richard Merrill

when comparing recombination rates, we always observe:

a) uniform recombination rates across different chromosomes

b) higher recombination rates in femals compared to males

c) A direct relationship between physical and genetic map length

Thomas Hunt Morgan and colleagues spent many years crossing wildtype and mutant fruit flies. If Morgan crossed a female fruit fly homozygous recessive at two linked loci controlling color and wing length (i.e. bb / vgvg), to a male fly heterozygous at both these loci (i.e. +b / +vg), what distribution of offspring genotypes is possible?

In the figure the star represents a recent mutation at a gene locus. The letters represent other loci. Which other locus is most likely to be in linkage disequilibrium with the mutation (all else being equal; assume a sexually reproducing organism)?

Which of the following statements about quantitative traits is not correct?

• Quantitave traits vary continuously

• Quantitative traits are normally determined by multiple alleles at multiple loci

• Qunatitative traits are not affected by the environment

• Quantiative traits can be affected by drift

• Quatitative traits can be affected by natural selection

Why are permutation tests commonly employed in QTL mapping studies? Choose the best answer

• To estimate effect size of identified QTLs accuretly

• To determine the staistical significance of QTLs as it allows us to correct for multiple testing

• To identify candidate genes associated with QTLs

• To directly manipulate the phenotypes of individuals in the mapping population

• to improve the resolution of QTL mapping by introducing additional genetic variation

Dobzhansky-Muller incompabilities (DMIs) …

What mechanisms may contribute to maintaining associations between traits involved in prezygotic isolation and those under divergent selection? Choose the best answer

• Random mating and genetic drift

• Physical linking, inversions, or pleitropy

• Hardy-Weinberg eqilibrium

• Homologous recombination

• Phenotypic plasticity

A very determined student is interested in two discrete traits, fore-wing color (black vs white) and hind-wing color (also black vs white), that vary across populations in a species of moth (where there is no recombination during egg production). Previously she studied these two traits independently, and has determined that: • Fore-wing color is controlled by a single locus (with two alleles), and that the black fore-wing allele is dominant over the white fore-wing allele, and • Hind-wing color is also controlled by a single locus (with two alleles), and that the black hind-wing allele is dominant over the white hind-wing allele. She now wants to consider these two traits together. F1 Generation all black fore and hind wings F2 200 offspring, 97 black black, 103 white white.' What is the conclusion?

a) that hind and forewing colour are pleiotropic effects of the same allele

b) that hind and forewing color are controlled by loci on the same chromosome

c) that hind an forewing color are controlled by loci on the Z (sex) chromosome

d) that hind and forewing colour are controlled by loci 48.5 cM apart

A very determined student is interested in two discrete traits, fore-wing color (black vs white) and hind-wing color (also black vs white), that vary across populations in a species of moth (where there is no recombination during egg production). Previously she studied these two traits independently, and has determined that: • Fore-wing color is controlled by a single locus (with two alleles), and that the black fore-wing allele is dominant over the white fore-wing allele, and • Hind-wing color is also controlled by a single locus (with two alleles), and that the black hind-wing allele is dominant over the white hind-wing allele.

F1: Ff Bb

Pop A: FF BB

Pop B: ff bb

second experiment:

In a second experiment she decides to additionally look at a third trait: Host plant

preference. Females from population A lay their eggs on the leaves of apple trees,

where as females from population B lay their eggs on the leaves of orange trees.

A literature search tells her that differences in host plant preference in this species are

genetically determined and are controlled by a single locus with two alleles, which are

co-dominant. In other words, heterozygote females have no preference.

She confirms this by assaying host preference in female offspring from her F1 cross

and finds that each of these hybrid females lays roughly equal numbers of eggs on

orange and apple leaves.

To look further at the genetics of host preference she mates a male from her F1 generation

to a female from population B. She assays a large number of female offspring from this

cross:

• 465 females with white fore-wings only lay eggs on orange leaves

• 585 females with black fore-wings lay on both apple and orange leaves

• 102 females with white fore-wings lay eggs on both apple and orange leaves

• 98 females with black fore-wings only lay eggs on orange leaves

Based on these data what is the genetic distance between the locus controlling fore-wing

colour and host preference?

Question 3

Your Uncle is a chicken enthusiast. He has recently acquired a small group of rare

Andalusian chickens. The Andalusian breed is unusual in that some individuals display a

distinctive slateblue plumage. This blue plumage of the Andalusian is caused by a

‘dilution gene’, which, in combination with a gene for black plumage, produces partial

dilution of the melanin, which normally gives the black colour. However, not all

Andalusians are blue:

• birds with two copies of the dilution allele (AA) have near total dilution à white

• birds with no copies of the dilution allele (aa) have no dilution, and are black

• birds with one copy of the dilution allele (Aa) have partial dilution, and are blue

Tending to his new flock, your uncle notices that one of his Andalusian females (which has

black plumage) is laying beautiful blue eggs. After a little reading, he suspects that the

blue eggs are the result of a mutation normally found in the Chilean chicken breed, the

Araucana. Egg colour is determined by maternal genotype

• Blue eggs are caused by a recessive allele b

à bb females produce blue coloured eggs

• Bb or BB females produce normal white eggs

i) Your uncle decides to mate a blue (plumage) male with this black (plumage) female

which lays blue eggs. He raises the first 20 eggs and finds among the offspring four

types of female phenotype combinations exist:

• Blue plumage and lay white eggs

• blue plumage and lay blue eggs

• black plumage and lay white eggs

• black plumage and lay blue eggs

From this information we can determine that the genotype of the father is:

A) AABB

B) Aabb

C) AaBb

D) aabb

Plumage colour is just one aspect of plumage. Assuming there are 6 diallelic loci

that influence plumage (size, shape, colour etc), how many possible 2n gamete

combinations (haplotypes) can be formed?

A) 12

B) 36

C) 64

D) 2080

in what measure is recombination rate measured ? And what does it determine?

In a linear regression plot, how can the h2 (narrow sense heritability) be derived?