Question

Genetics: Please explain your work. Will give a thumbs up. Thank you.

1. If the observed percentage of recombination between 2 loci is converted to cM.

A. the cM value will always be smaller than the % recombination

B. the cM value can be converted to the number of base pairs of DNA and this value will be equal for all chromosomes regions

C. The cM value can be greater than the % recombination at vlaues of 10% recombinantion and greater

D. the cM value can never be greater than 50

E. all of the above

2. Consider 2 genes in peas-gene controlling seed color-yellow Vs green; gene controlling seed texture-smooth Vs wrinkled. Assume the two genes are very tightly linked. A true breeding smooth green plant is crossed to a true breeding wrinkled yellow. All the F1 progeny were smooth yellow. The F1 generation were self-fertilized. In the F2 what is the expected ratio of the phenotypes- smooth and yellow and green: wrinkled and yellow; wrinkled and green.

a. 9:3:3:1

b. 1:0:1:0

c. 2:1:1:0

d. 0:1:1:0

e. 1:1:1:1

Answer 1

1. Option D is the correct answer. 1 cM indicates 1% recombination and frequency of recombination can never be greater than 50 because maximum possible rate of recombination for any gene sequence is 50%.

2. Option b is the correct answer. Here all the f2 progeny are smooth yellow. It means the genotype for F1 progeny will be either (SSyy or Ssyy). Either of the two possible genotype will not produce green colour upon self fertilization because yellow color is recessive and only expresses in homozygous recessive condition and thus, there is no chance of green colour in F2 progeny.