QUIZ 3

Question 1

A man whose grandfather on this mother’s side had favism (a rare X-linked recessive sensitivity to broad beans) marries a woman whose uncle on her mother’s side also had favism. What is the probability (as a percentage) that their 1st child will have favism? Put a number in the box. Hint: Draw the pedigree

Answer 1

6.25

Question 2

Let’s brush up on mapping. For Qs 2-8, pure-breeding P0 animals were mated to generate F1 animals heterozygous at the B and W genes. The heterozygous F1 animals were test-crossed and yielded progeny with the phenotypes below. Recessive mutations in the B gene cause a “no bristles” phenotype. Recessive mutations in the W gene cause a “no wings” phenotype.

38% no bristles, normal wings
38% normal bristles, no wings
12% no bristles, no wings
12% normal bristles, normal wings

The numbers above suggest that the B and W genes are linked. What ratio of progeny would you have expected to see if B and W were on different chromosomes?

Answer 2

25% normal bristles, normal wings; 25% no bristles, no wings; 25% no bristles, normal wings; 25% normal bristles, no wings

Question 3

What were the genotypes (correctly written) of the pure-breeding P0 animals?

Answer 3

Bw/Bw and bW/bW

Question 4

Now continue working with the F2 progeny presented in Q2. Which of the progeny categories are “parental’?

Answer 4

no bristles, normal wings and normal bristles, no wings

Question 5

In the heterozygous F1 animals, are the alleles in the cis or trans configuration?

Answer 5

trans

Question 6

In the heterozygous F1 animals, in what % of meiotic events was there a cross-over in the B-W interval (ex: btwn the B and W genes)? Put a number in the box.

Answer 6

48

Question 7

What is the distance (in m.u.) btwn the B and W genes? Put a number in the box.

Answer 7

24

Question 8

If heterozygous F1 animals had been crossed with each other, what % of their progeny would you expect to have no bristles and no wings? You can assume that crossing over can occur in both parents. Put a number in the box.

Answer 8

1.44

Question 9

A 3-point cross btwn a heterozygous mother (Mabel) and a tester male gave the offspring below, where b, f, g are recessive and B, F, and G are the wild-type alleles. What is Mabel’s genotype, showing the correct order of genes?

B F G - lots
b f g - lots
b F G - some
B f g - some
b F g - some
B f G - some
b f G - very few
B F g - very few

Answer 9

B G F / b g f