Question

some people have freckles, and some people do not have freckles. if a child has freckles, at least one parent has freckles. however, the child may have a sibling that does not have freckles. which statement best describes the presence of freckles?

freckles are not determined by dna.
there are two alleles for freckles.
there is no dominant allele for freckles.
freckles are determined by two genes instead of by one.

Explanation:

• Freckles are genetic traits, so they are determined by DNA. This rules out the first option.
• If a child has freckles and a sibling does not, and at least one parent has freckles, it suggests a simple Mendelian inheritance pattern. In Mendelian genetics, for a trait like this, there are usually two alleles (e.g., dominant and recessive).
• The fact that a child can have freckles while a sibling does not (when at least one parent has freckles) implies there is a dominant allele (since if a parent has the dominant allele, they can pass it on. If both parents are heterozygous - having one dominant and one recessive allele - they can produce offspring with or without the trait). So the third option is incorrect.
• There is no indication from the given information that two genes are involved. Simple single - gene (two - allele) inheritance can explain the described pattern.

Answer:

There are two alleles for freckles.