In the following cross, the genes are inherited independently except for C and D

Question

In the following cross, the genes are inherited independently except for C and D, which are tightly linked and show zero recombination: A/A ; b/b ; c/c ; D/D ; e/e ; F/F × a/a ; B/B ; C/C ; d/d ; E/E ; f/f. In the F2, what proportion of individuals will be:

a) pure breeding?

b) heterozygous for all loci?

c) homozygous recessive for all loci?

d) A/a;B/B;c/c;D/D;E/e;f/f?

e) phenotypically like either parent?

f) phenotypically unlike either parent?

g) genotypically like either parent?

h) genotypically unlike either parent?

Explanation / Answer

The F1is of the following constitution: A/a; b/B; c D/Cd; e/E; F/f. The C and D loci behave like one locus.

a) ½x½x½x½x½= 1/32

b) ½x½x½x½x½= 1/32

c) zero because of the trans arrangement of c and d

d) ½x¼x¼x½x¼ = 1/256

e) (¾x¼x¼x¼x¾) + (¼x¾x¼x¾x¼) = 18/1024

f) subtract answer of“e)” from 1; answer = 1006/1024

g) (¼x¼x¼x¼x¼) + (¼x¼x¼x¼x¼) = 2/1024 = 1/512

h) subtract answer of “g)” from 1; answer = 511/512

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