Question

this passage describes the scale type trait in common carp: carp are large freshwater fish that are often raised for food. before a carp is cooked, its scales are usually removed. normally, carp are covered in small scales arranged in straight rows. but carp with mirror scales have large scales arranged in scattered patches. because mirror scales do not cover the fishs entire body, carp with mirror scales are easier to prepare for cooking. in a group of common carp, some individuals have normal scales and others have mirror scales. in this group, the gene for the scale type trait has two alleles. the allele for normal scales (a) is dominant over the allele for mirror scales (a). a certain common carp from this group has mirror scales. based on this common carps phenotype for the scale type trait, which of the following could be its genotype for the scale type gene? select all that apply. aa aa aa

Explanation:

Step1: Understand dominant and recessive alleles

In genetics, a dominant allele (A) masks the expression of a recessive allele (a). So, for a recessive phenotype (mirror scales in this case), the organism must have two recessive alleles.

Step2: Analyze each genotype

• For \(AA\): The dominant allele \(A\) is present. The phenotype would be normal scales (since \(A\) is dominant over \(a\)).
• For \(Aa\): The dominant allele \(A\) is present. The phenotype would be normal scales ( \(A\) masks \(a\)).
• For \(aa\): There are no dominant alleles. The recessive allele \(a\) is expressed, so the phenotype is mirror scales.

Answer:

aa