Answer:
a) 25%; b) 50%; c) 45%; d) 38%
Explanation:
<h3 /><h3>a) Unlinked genes</h3>
A/A B/B X a/a b/b
F1: A/a B/b
Testcross A/a B/b X a/a b/b
The homozygous recessive individual only produces <em>ab</em><em> </em>gametes.
The F1 produces four types of gametes (each of them with a frequency of 1/4): <em>AB</em>, <em>Ab</em>, <em>aB </em>and <em>ab</em>.
25% of the progeny will be a/a b/b.
<h3>b) Completely linked genes</h3>
AB/AB X ab/ab
F1: AB/ab
Testcross AB/ab X ab/ab
The F1 produces only two types of gametes, the parentals (each of them with a frequency of 1/2): <em>AB</em> and <em>ab</em>.
50% of the progeny will be ab/ab.
<h3>c) 10 m.u. apart</h3>
AB/AB X ab/ab
F1: AB/ab
Testcross AB/ab X ab/ab
The F1 produces four types of gametes, the parentals <em>AB</em> and <em>ab </em>and the recombinants <em>Ab</em> and <em>aB</em>.
Since the genes are 10mu apart, 10% of the produced gametes will be recombinant and 90% will be parentals. Since there are two types of parental gametes, each of them has a frequency of 45%.
45% of the progeny will be ab/ab.
<h3>d) 24 m.u. apart</h3>
This is very similar to c).
Since the genes are 24mu apart, 24% of the produced gametes will be recombinant and 76% will be parentals. Since there are two types of parental gametes, each of them has a frequency of 38%.
38% of the progeny will be ab/ab.
