Question

An individual that is heterozygous for type B blood and little finger shape mates with an individual that is heterozygous for type A blood and homozygous dominant for a bent little finger. What is the predicted genotypic ratio for this cross?
A. 9:3:3:1
B. 1:2:1
C. 1:1:1:1:1:1:1:1
D. 2:1:2:1:4:1:2:1
E. 1:1:1:1

Answer 1

Answer:

The correct option is E) 1:1:1:1

Explanation:

A punnet square in which only a single trait is being studied is a monohybrid cross. A cross in which two traits are being studied in a dihybrid cross.

As two traits are being studied in the question, hence a dihybrid cross will be made as follows:

          A-F     A-F     OF         OF

Bf     ABFf    ABFf      BOFf      BOFf

Bf    ABFf     ABFf      BOFf      BOFf

Of    AOFf    AOFf      OOFf     OOFf

Of    AOFf    AOFf      OOFf     OOFf

The results of the punnet square show that there are

• 4/16 chances for the offspring to have the genotype ABFf

• 4/16 chances for the offspring to have the genotype BOFf

• 4/16 chances for the offspring have the genotype AOFf

• 4/16 chances for the offspring to have the genotype OOFf

Hence, there will be an equal ratio of 1:1:1:1 for each of the genotype.

Answer 2

Answer: the correct answer is E