Blonde hair (bb) is a recessive trait and brown hair (Bb) is dominant. If both parents have brown hair, what must be true if one of their children have blonde hair?
A. Both parents must be hybrid with regard to hair color (Bb)
B. Both parents have two brown hair genes (BB)
C. One parent must have two blonde hair genes (bb) whole the other has two brown hair genes (BB)
D. One parent must have two genes for blonde hair (bb) and the other must be hybrid for hair color (Bb)
!Missing this part of my book please help!
To determine the answer, let's first understand the concept of hair color inheritance. In this scenario, blonde hair (bb) is a recessive trait, while brown hair (Bb) is dominant.
If both parents have brown hair (Bb), it means that they each have one gene for brown hair and one gene for blonde hair. Since brown hair is dominant, only one copy of the brown hair gene is needed for it to be expressed. Blonde hair, being recessive, needs both copies of the gene to be present for it to be expressed.
Now, if one of their children has blonde hair, it means that the child must have received a blonde hair gene from both parents. This can only occur if both parents are hybrid or heterozygous for hair color (Bb) and carry the recessive blonde hair gene.
Therefore, the correct answer is:
A. Both parents must be hybrid with regard to hair color (Bb).
Based on the information given, if both parents have brown hair but one of their children has blonde hair, the most likely scenario is that both parents are heterozygous or hybrid for hair color (Bb).
This means that one parent has one dominant brown hair gene (B) and one recessive blonde hair gene (b), while the other parent also has one dominant brown hair gene (B) and one recessive blonde hair gene (b).
Therefore, the correct answer is A. Both parents must be hybrid with regard to hair color (Bb).
http://www.khanacademy.org/science/biology
Scroll down to the sections on genetics and read everything carefully.