Question

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 C^AC^BD^WD^O is mated to a C^BC^BD^OD^O guinea pig. The resulting progeny are evaluated and the following classes produced in these numbers:

C^AC^BD^OD^O        326  

C^BC^BD^WD^O       420

C^AC^BD^WD^O        73  

C^BC^BD^OD^O          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?

Answer 1

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.

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

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.