R A Emerson crossed two different purebreeding lines of corn

R. A. Emerson crossed two different pure-breeding lines of corn and obtained a phenotypically wild-type F1 that was heterozygous for three alleles that determine recessive phenotypes: an determines anther; br is brachytic; and f is fine. He testcrossed the F1 with a tester that was homozygous recessive for the three genes and obtained these progeny phenotypes: 355 anthers: 339 brachytic, fine; 88 completely wild type; 55 anthers, brachytic. fine; 21 fine; 17 anthers, brachytic; 2 brachytic; 2 anthers, fine. Note that if a phenotype Is not mentioned then it is assumed to be WT. Draw a linkage map for the three genes (include map distances). Calculate the interference value. What were the genotypes of the parental lines? Draw them in chromosome format.

Solution

Total genotypes = 879

Total parental types = 88+55 =143

Total recombinants = 879-143 = 736

Recombination frequency = (total recombinants / total)*100 = 736/879 = 83.73% is the recombination frequency.

These genes are not linked.

For linkage to happen parental types should be greater than the number of recombinants.

Brachytic is in middle

Anther----------------brachytic----------------fine (Answer \'a\')