Question a (2 pts) A red, round, true-breeding tomato is bred with a yellow, ova

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Question a (2 pts) A red, round, true-breeding tomato is bred with a yellow, oval, true-breeding tomato, and the F1s are testcrossed to a homozygous-recessive tester. This results in the offspring below.

            yellow oval        11

            red round           14

            yellow round        7

            red oval               8     

a) Calculate the chi-squared value to test the likelihood of linkage.

b) What is your conclusion?

Question b (2 pts) An F1 guinea pig with the genotype CACBDWDO is mated to a CBCBDODO guinea pig. The resulting progeny are evaluated and the following classes produced in these numbers:

CACBDODO        326  

CBCBDWDO       420

CACBDWDO        73  

CBCBDODO          84

a. What were the genotypes of the parental true breeding guinea pigs that produced the F1?

b. What is the distance between the genes in cM?

Explanation / Answer

Red - RR and Yellow - rr

Round - WW and oval - ww.

The genotype of red and round true-breeding tomato - RRWW.

The genotype of yellow and oval true-breeding tomato - rrww.

Cross between them RRWW X rrww

Gametes formed RW rw

F1 Generation RrWw.

Test cross RrWw X rrww

Gametes formed RW, rW, Rw and rw rw.

Next generation - RrWw , rrWw, Rrww and rrww

Genes are not linked and follow test cross ratio 1:1:1:1.

X2= (11-10)2/10+(14-10)2/10+(7-10)2/10+(8-10) 2/10

=0.1+1.6+0.9+0.4

= 3.0

Degree of freedom = 4-1 =3

At P = 0.05,df=3

Our value is less(7.6 is table value) and if the calculated chi-square value is less than the 0 .05 value, we accept the hypothesis.

Observed Expected yellow oval 11 10 red round 14 10 yellow round 7 10 red oval 8 10 total 40 40

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