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Genetic 342 A&B

Kenneth G Wilson

Professory of Botany

In the case of three genes it is just a simple extension of two genes.

Assume that you have three genes a, b, and c (a+, b+, c+) and the order of the genes are a-b-c ie b is the center gene.

The test cross is (a b c/a+ b+ c+) x (a b c / a b c)

Let f=0.2 (20 cm) which is the frequency of crossing over between a and b and

let g=0.1 (10 cm) which is the frequency of crossing over between b and c.

What are the expected ratios of progeny?

Description genotype P

f=.2
g=.1

 N=1000

Parental type one

 a+ b+ c+ (1-f-g)/2 0.35 350
Parental type two a b c (1-f-g)/2 0.35 350

Region I Recombinant

a+ b c

 f(1-g)/2 0.09 90
Region I Recombinant a b+ c+ f(1-g)/2 0.09 90
Region II Recombinant abc+ g(1-f)/2 0.04 40
Region II Recombinant a+b+c g(1-f)/2 0.04 40
Double C/O a+bc+ f*g/2 0.01 10
Double C/O ab+c f*g/2 0.01 10

 

oliver

This is our friend Oliver the parrotlet,

Oliver is a true parrot,

the smallest in the world.