The table lists the hair color and genotype of six individuals where black hair is dominant over blond. Use the table to answer any questions that follow.
HAIR COLOR
Name Hair color Alleles
Mr. Johnson black homozygous
Mrs. Johnson blond homozygous
Mr. Valdez blond heterozygous
Mrs. Valdez black heterozygous
Mr. Ellwood black heterozygous
Mrs. Ellwood blond homozygous
If Mr. and Mrs. Johnson had four children together, what color of hair would the children likely have?
a
All 4 of the children would have black hair.
b
Only 3 of the children would have black hair, and 1 child would have blond hair.
c
All 4 of the children would have blond hair.
d
Only 2 of the children would have black hair, and 2 of the children would have blond hair.
The correct answer is b) Only 3 of the children would have black hair, and 1 child would have blond hair.
This is because Mr. Johnson has black hair and is homozygous for the black hair allele, while Mrs. Johnson has blond hair and is homozygous for the blond hair allele. Since black hair is dominant over blond hair, all of the children would receive one allele for black hair from Mr. Johnson. However, since Mrs. Johnson is homozygous for the blond hair allele, all of the children would receive one allele for blond hair from her as well. Therefore, 3 of the children would have black hair (heterozygous) and 1 child would have blond hair (homozygous).