Blonde hair (b) is recessive and black hair (B) is dominant. A woman with black hair marries a man with blonde hair who is homozygous recessive for blonde hair. Predict the outcome of their children when the woman is homozygous for black hair.

1) How many of the offspring would you expect to have blonde hair ?

(2)How many of the offspring would you expect to have black hair?

Thanks in advance.

Question

Blonde hair (b) is recessive and black hair (B) is dominant. A woman with black hair marries a man with blonde hair who is homozygous recessive for blonde  hair. Predict the outcome of their children when the woman is homozygous for black hair.

1)	How many of the offspring would you expect to have blonde hair ?

(2)How many of the offspring would you expect to have black hair?

Thanks in advance.

micahmglomski · Answer

1. Using the alelles "H" for straight hair and "h" for curly hair, the mother has the genotype hh while the father has the genotype HH. The only possible genotype outcome for any potential children would be Hh - 100% heterozygous dominant for straight hair. 

genotype ratio - 4:0 Hh 
phenotype ratio - 4:0 straight hair 

2. Black hair = BB, brown hair = Bb, blonde hair = bb 

Since both parents have brown hair (which is heterozygous), each of them has the genotype Bb. Using a Punnett Square, you get the four following possible genotypes - BB, Bb, Bb, and bb. The children have a 25% chance of having either black hair, 25% chance for blonde hair, and 50% chance for brown hair. 

genotype ratio - 1:2:1 (BB: Bb: bb) 
phenotype ratio - 1:2:1 (black, brown, blonde)
Source(s):
These are the most basic Punnett Square scenarios. If you actually read the textbook, it should be pretty clear how to calculate these problems.

anonymous · Answer

Very precise. Thank you so much.