Exhibits, Shows and Displays

If an individual exhibits a recessive trait, which of the following statements must be correct?

A. Any siblings of this individual will have the same phenotype for this trait. B. This individual's genotype is different from an individual with the dominant trait. C. Both parents of this individual had the same genotype for this trait. D. Any children this individual has will always exhibit the trait, regardless of the genotype of the other parent. E. This individual is heterozygous

Public Comments

1. b. This individual's genotype is different from an individual with the dominant trait. For example, in order to have blue eyes, a person must have the genotype bb. If they are BB or Bb, they would have brown eyes. Just remember that in order to show a recessive trait, an individual must be homozygous for that trait. It can't be a, because if the parents were both heterozygous (Bb), different children may have different genotypes (for example, my children have different color eyes - one blue, one brown). The parents would have a 75% chance of having a child with brown eyes, and a 25% chance of having a child with blue eyes. It can't be c, because the parents could be Bb and bb (different genotypes), and they would have a 50% chance of having a child with blue eyes (bb) It can't be d, because if this individual marries a person with brown eyes, their children could have brown eyes. It can't be e because, as mentioned above, a person must be homozygous for the recessive trait in order to exhibit it.
2. That would be "C"
3. A. Incorrect. If either parent has a dominant allele, the siblings might have received it. B. Correct. C. Incorrect. They could both be heterozygous or one or both could be recessive homozygous. D. Incorrect. If the other parent possesses and passes on a dominant allele, their child will have dominant phenotype. E. Incorrect. Exhibiting a recessive trait means you're recessive homozygous by definition.
4. If an individual is exhibiting a recessive trait, then this individual is homozygous recessive (rr). The answer is B. This is because the individual with dominant trait would either be homozygous dominant (RR) or heterozygous (Rr). Thus this person would have different genotype than recessive trait individual. Rest of the options are not true.