Suppose gene A is on the X chromosome, and genes B, C, and D are on three differ
ID: 12646 • Letter: S
Question
Suppose gene A is on the X chromosome, and genes B, C, and D are on three different autosomes. Thus, A_ signifies the dominant phenotype in the male or female. An equivalent situation hold for B_, C_, and D_. The cross AA BB CC DD female x aY bb cc dd male is made.a. what is the probability of obtaining an A_ individual in the F1 progeny?
b. What is the probability of obtaining an a male in the F1 progeny?
c. What is the probability of obtaining an A_B_C_D_ female in the F1 progeny?
d. How many different F1 genotypes will there be?
e. what proportion of F2 individuals will be heterozygous for the four genes?
f. determine the probabilities of obtaining each of the following types in the F2 individuals (1) A_bbCCdd (female) (2) aYBBCcDd (male) (3) AYbbCCdd (male) (4) aabbCcDd (female)
Explanation / Answer
a. 1, the female is AA, so regardless what the male has, it will have one A and will be designated A_.
b. 1/2, the male is aY, so there's one in 2 chances that the Y is given instead of the a (which would result in a male).
c. If chances of getting a male is 1/2, chances of getting a female is 1/2. Similarly to (a), the female is BB, CC, and DD, so regardless what the male has, the offspring will be designated B_, C_, and D_. So, (1/2)(1)(1)(1)=1/2.
d. 2, the female one and the male one
e. F1 female (AaBbCcDd) x F1 male (AYBbCcDd)
for A: offspring AA: Aa: AY: aY=1:1:1:1, so probability of Aa: 1/4
for B: offspring BB: Bb: bb=1:2:1, so probability of Bb: 2/4=1/2
similar to B, probability of Cc: 1/2 and probability of Dd: 1/2
So, (1/4)(1/2)(1/2)(1/2)=1/32
f. Looking at the offspring possible in (e),
(1) probability of A_ female: 2/4=1/2, probability of bb: 1/4, probability of CC: 1/4, probability of dd: 1/4 (1/2)(1/4)(1/4)(1/4)=1/128
(2) probability of aY: 1/4, BB: 1/4, Cc: 1/2, Dd: 1/2 (1/4)(1/4)(1/2)(1/2)=1/64
(3) probability of AY: 1/4, bb: 1/4, CC: 1/4, dd: 1/4 (1/4)(1/4)(1/4)(1/4)=1/256
(4) probability of aa: not possible, so 0