3. In junior high students a bad attitude (B) is dominant to a good attitude (b). Two
parents, a father with a bad attitude in junior high and a mother with a good attitude in
junior high, produce 10 children. Half have a good attitude in their junior high school
years and half have a bad attitude in their junior high school years. What is the
genotype of their parents?

The parents genotypes are as follows:

Father: Bb

Mother: bb

Explanation: From the information given above, bad attitude (B) is dominant to good attitude (b). An individual who is heterozygous for bad attitude will have Bb genotype and will manifest phenotypically as bad attitude. Good attitude is recessive, therefore a woman with good attitude has a genotype bb.

When Bb crosses with Bb, the possible genotypes of the offsprings are 2Bb and 2bb. This means that Bb x bb = Bb, Bb, bb and bb.

Half of the offsprings are Bb (bad attitude) while half of the offsprings are bb (good attitude).

Therefore, if a man with genotype Bb and a woman with genotype bb have 10 children, half of the offsprings will have bad attitude with genotype Bb while the other half will have good attitude with genotype bb.