Question

After learning in biological anthropology class that a cleft chin is recessive and that dimples, a free-hanging earlobe, and tongue rolling are dominant, your friend tells you over dinner that she is certain she is adopted. What could have caused her to arrive at this conclusion?

Answer 1

Both of her parents have a cleft chin but she doesn't

Step-by-step explanation:

Alleles

C - NOT a cleft chin (dominant gene)

c - a cleft Chin (recessive gene)

Possibilities of Genotype

CC - NOT a Cleft chin

Cc - NOT a Cleft chin (since C is dominant )

cc - a Cleft chin

Now, we both know that her parents have Cleft chin, which means that both of them could only have cc as their genotype.

This mean, if they have children ,both the father and the mother could only give c alleles. This make the possibilities of their child having a cleft chin become 100%.

If the girl does not have a cleft chin, we can say that she is 100% not the biological child of the parents.