You are investigating 4 recessive alleles in corn. They are whimpy ears (w), striped leaves (s), shriveled kernels (k), and red tassels (r). Their dominant counterparts are represented by the "+" symbol. A plant that is homozygous recessive for all four genes (ww ss kk rr) is crossed with a plant that is homozygous dominant for all four genes (++ ++ ++ ++). The F1 progeny (w+ s+ k+ r+) are then testcrossed with another plant. A total of 1000 F2 progeny were produced. The F2 progeny display the following phenotypes.
|
Phenotype
|
Observed # of Progeny
|
|
w s k r
|
198
|
|
+ + + +
|
202
|
|
w s k +
|
201
|
|
+ + + r
|
199
|
|
w + k +
|
49
|
|
+ s + r
|
51
|
|
w + k r
|
48
|
|
+ s + +
|
52
|
a. Calculate the recombination frequencies between each pair of genes. (HINT: you will calculate 6 recombination frequencies - determine where each pair of genes experienced a crossover to produce the observed offspring).
b. Draw a chromosome map for these genes if they are linked.