Having Unattached Earlobes, is a dominant allele Attached earlobe shape is recessive. A parent with attached earlobes has a child with a parent with unattached earlobes: Which of the following correctly identifies the phenotype of the parent with the attached earlobe shape? heterozygous homozygous recessive attached earlobes ee
The Correct Answer and Explanation is:
The parent with attached earlobes must be homozygous recessive. Here’s an explanation of why:
Earlobe attachment is determined by a simple Mendelian inheritance pattern, where the allele for unattached earlobes (let’s use “A”) is dominant and the allele for attached earlobes (let’s use “a”) is recessive. So, individuals with unattached earlobes can either be homozygous dominant (AA) or heterozygous (Aa), while individuals with attached earlobes must be homozygous recessive (aa) because the recessive allele will only be expressed when two copies are present.
Now, let’s look at the parental scenario.
- The parent with attached earlobes has the phenotype attached earlobes, and since the attached trait is recessive, this parent must have two recessive alleles, making them homozygous recessive (aa).
- The parent with unattached earlobes has at least one dominant allele, so they could either be heterozygous (Aa) or homozygous dominant (AA).
When these parents have a child, the child will inherit one allele from each parent. The parent with attached earlobes (homozygous recessive) can only pass on the a allele, while the parent with unattached earlobes will pass on either an A or an a allele, depending on whether they are heterozygous or homozygous.
Thus, for the parent with attached earlobes, their genotype is homozygous recessive (aa), and this is the correct way to identify their phenotype.
