Question

Attached earlobes are a recessive trait in humans. In the tree below, people with attached earlobes are shaded in. Which best describes the person labeled X in the tree?

C. A male with one recessive allele.
D. A male with no recessive alleles.

Answer 1

Without additional information or a clearer family tree, the genotype of person X, presumed to be a male regarding attached earlobes, cannot be determined with certainty. It can only be said that X has free-hanging earlobes, which is a dominant trait, so X has at least one dominant allele.

Step-by-step explanation:

The question pertains to the inheritance pattern of attached earlobes, which is a recessive trait. Given that attached earlobes are recessive and person X in the family tree does not have attached earlobes, we can infer that person X at the very least carries one dominant allele since they do not exhibit the recessive phenotype. Without further genetic information or a clearer depiction of the family tree, it's impossible to conclude whether person X carries a recessive allele. However, since option C suggests that person X is a male with one recessive allele, this cannot be determined from the information given. The presence of a dominant allele is enough to display the dominant phenotype of free-hanging earlobes. Therefore, option D, which states that person X is a male with no recessive alleles, cannot be determined without assuming that person X is homozygous dominant, which is again not specified in the family tree. To correctly determine the genotype of X, one would need more information about X's parents or offspring. In general, free-hanging earlobes are an autosomal dominant trait, and the presence of the dominant allele (F) is enough for the trait to be displayed.

Answer 2

The answer is a C. The offsprings from this generation are from a cross between parents who are heterozygous (one parent) and homozygous recessive. This means that all the offsprings of the filial 1 (one) generation will carry a recessive allele. However, those with an equivalent dominant allele will not exhibit the attached earlobe trait. This is shown by the Punnet square below;