Question

How many different offspring genotypes are expected in a trihybrid cross between parents heterozygous for all three traits when the traits behave in a dominant and recessive pattern? How many phenotypes?
64 genotypes; 16 phenotypes
16 genotypes; 64 phenotypes
8 genotypes; 27 phenotypes
27 genotypes; 8 phenotypes

Answer 1

Answer:

27 genotypes and 8 phenotypes

Explanation:

Supposing that the genotypes of both of the parents are AaBbDd (A, B and D are dominant over a, b and d).  After completing the Punnett square, you can predict the following offspring:

I add an image where you can see all the 27 genotypes and frequencies.

Finally, all the 8 phenotypes with the following frequencies:

27/64 A-B-D-

9/64   A-B-dd

9/64   A-bbD-

9/64   aaB-D-

3/64   A-bbdd

3/64   aaB-dd

3/64   aabbD-

1/64    aabbdd

Total 64/64

Note: when a phenotype is A-, it means that it came from either genotype, AA or Aa. The same applies to B- (BB or Bb) and D- (DD or Dd)