Question

What fraction of offsprings of the cross $AaBbDdEEFf\times AaBBDdEeFf$ are homozygous for all the genes, assuming that they are on different chromosomes?

• A. $1/32$
• B. $1/64$
• C. $1/8$
• D. $1/4$

Answer 1

Answer: (B)

$1/64$

In the given problem, the one parent has genotype AaBbDdEEFf and the other parent has genotype AaBBDdEeFf.

For gene A, there will be cross of Aa X Aa. The probability of having a homozygous phenotype, that is either AA or aa is 2/4 = 1/2.

For gene B, there will be cross of Bb X BB. The probability of having a homozygous phenotype, that is BB is 1/4.

For gene D, there will be cross of Dd X Dd The probability of having a homozygous phenotype, that is either DD or dd is 2/4 = 1/2.

For gene E, there will be cross of EE X Ee. The probability of having a homozygous phenotype, that is EE is 1/4.

For gene F, there will be cross of Ff X Ff. The probability of having a homozygous phenotype, that is FF or ff is 2/4 = 1/2.

Hence, the probability of offsprings having all the homozygous genes (either dominant or recessive) will be 2 X (1/2 X 1/4 X 1/2 X 1/4 X 1/2) = 2/128 = 1/64.

Thus, the correct answer is option B.