Question

Punnett squares can help us predict the probability of certain traits being passed down family lines. Suppose your maternal grandparents had a phenotype of brown hair with genotypes of Bb and BB. Your paternal grandfather has brown hair (Bb,) and your paternal grandmother has blonde hair (bb.) What is the probability that you will have brown hair?

Answer 1

The chance for you to have brown hair would be 75% based on your parent's genotypes. This is calculated using Punnett squares and applying simple Mendelian genetics, where brown hair is considered the dominant trait.

Step-by-step explanation:

In this case, the Punnett squares would help to determine the potential hair color. The mother's possible gene contributions are BB (brown hair) from her BB genotype grandparents and Bb (brown hair) from her Bb genotype grandparents. This results in her always contributing a B allele (brown). The father's possible gene contributions are B (brown) from the Bb grandfather or b (blonde) from the bb grandmother. The resulting Punnett squares would be BB, Bb, Bb, and bb. However, because brown hair is dominant over blonde, bb is the only genotype that would express blonde hair. Therefore, the chances for you to have brown hair would be 75% (BB, Bb, and Bb) and a 25% chance of having blonde hair (bb).

Learn more about Punnett squares