Which statement or factor is a criterion for autosomal-recessive transmission of single-gene traits?
A)About 25% of the members of a large kindred with an autosomal-recessive trait will express the trait.
B)There is no carrier status; if the allele for the trait is present, it is expressed, although the degree of expression can be variable.
C)Individuals who are heterozygous for an autosomal-recessive trait have minimal risk for transmitting the allele to their offspring.
D)The degree of expression of an autosomal-recessive trait or disorder in a homozygous individual is directly related to the penetrance of the trait.

Question

Quizplus · Accepted Answer

Because autosomal-recessive traits or disorders are only expressed in the homozygous state, expression of the trait or disorder within a large kindred remains at a relatively constant level of no greater than about 25%. The heterozygous individual is a carrier who has a 50% chance with each pregnancy of transmitting the allele to his or her offspring. There is no evidence to support the presence of the concept of "penetrance" in autosomal-recessive traits and disorders. This issue appears to be associated only with dominant traits and disorders.

Which Statement or Factor Is a Criterion for Autosomal-Recessive Transmission