Question

In the following tetrahybrid cross AaBbCcDd x AaBbCcDd what proportion of the F2 offspring would be expected to be genotypically AABBCCdd?

A. 3/4
B. 1/2
C. 1/256
D. 81/256
E. 9/256

Answer 1

C. 1/256

Step-by-step explanation:

In the tetrahybrid cross, we have different four groups. Let name them Part (A, B, C & D).

Let Part A be Aa and Aa... If both traits crosses; we have

A a

A AA Aa

a Aa aa

Hence, there is a total of 4 combinations

Let Part B be Bb and Bb... If both traits crosses; we have

B b

B BB Bb

b Bb bb

Hence, there is a total of 4 combinations

Let C be Cc and Cc ... If both traits crossses; we have

C c

C CC Cc

c Cc cc

Hence, there is a total of 4 combinations

Let D be Dd and Dd... If both traits crosses; we have

D d

D DD Dd

d Dd dd

Hence, there is a total of 4 combinations

A genotype has the 4 groups together. Therefore the possible number of ways of forming the genotype = 4 x 4 x 4 x 4= 256

Now, Probability that the F2 offspring would be expected to be genotypically AABBCCdd =
`(number of genotype AABBCCdd)/(Total number of genotype in the offsprings)`

=
`(1)/(256)`