Question

The ability to roll the tongue is caused by a dominant allele. A woman is a ""roller,"" but one of her parents is not. The woman is expecting a child with a man who is a nonroller. What is the probability that their first child will be a roller?

a. 1/4
b. 0
c. 3/4
d. 1/2
e. 1

Answer 1

The probability that the first child will be a roller is 1/2 or 50%.

Step-by-step explanation:

The ability to roll the tongue is determined by a dominant allele. In this case, the woman is a 'roller' but one of her parents is not. The woman's genotype is likely heterozygous (Rr), with the dominant allele for rolling (R) and the recessive allele for non-rolling (r). The man is a nonroller and his genotype is likely homozygous recessive (rr). When we cross these genotypes, the Punnett square predicts that there is a 50% chance (or 1/2 probability) of their first child being a roller with the genotype Rr.