Question

in the pedigree, myron’s parents are represented by a circle and square in the top row. the three sons of the parents are represented by squares in the second row. the shaded square represents the son who expresses the trait that myron is studying. the pedigree provides the strongest evidence for which of these conclusions? what can be concluded about the trait? a. the trait is harmful, and may be a genetic disorder. b. the allele for the trait is dominant. c. the allele for the trait is recessive. d. only males may express the trait.

Explanation:

1. Analyze Option A: The pedigree shows only one son with the trait, but we can't conclude it's harmful or a disorder just from this. Harmfulness isn't determined by pedigree structure alone.
2. Analyze Option B: If the allele were dominant, at least one parent should show the trait (since dominant traits are expressed if present). Here, parents (top - row square and circle) don't show the trait, so dominant is unlikely.
3. Analyze Option C: Since parents don't show the trait (unshaded) but a son does (shaded), this fits a recessive allele pattern. Recessive alleles can be carried by parents (heterozygous, so not expressing the trait) and expressed in offspring when homozygous.
4. Analyze Option D: The pedigree has only male offspring shown, but we can't conclude only males express it (there could be female offspring not shown, or the trait could be autosomal recessive with this male being the one to inherit two recessive alleles).

Answer:

C. The allele for the trait is recessive.