Question

which statements about alleles are correct? select all that apply.
if someone refers to \the gene for red hair,\ they really mean \the allele for red hair.\ the gene is for hair color; different alleles are associated with different colors of hair.
alleles differ in their structural sequences only—not their regulatory sequences. thus, each allele of a gene codes for an rna or protein product that has a different primary sequence.
alleles that only differ in the base sequence of regulatory elements can be associated with different phenotypes.
an allele can be defined by any difference—even a tiny one—in either the structural or regulatory segments of a gene.

Explanation:

• First statement: A gene is a general unit, and alleles are specific variants. So, when someone says "the gene for red hair," they actually mean the allele (a specific form of the gene) for red hair as the gene is for hair - color in general. This statement is correct.
• Second statement: Alleles can differ in both structural (coding) and regulatory sequences. Regulatory sequence differences can affect when and how much of a protein is made, not just the primary sequence of the protein. So, this statement is incorrect.
• Third statement: Alleles that differ in regulatory elements can lead to different phenotypes. For example, a regulatory - sequence change might cause a gene to be expressed more in one tissue than another, leading to a phenotypic difference. This statement is correct.
• Fourth statement: An allele is defined as any variant (even a single - base difference) in either the structural (coding) or regulatory parts of a gene. This statement is correct.

Answer:

• The first statement: If someone refers to "the gene for red hair," they really mean "the allele for red hair." The gene is for hair color; different alleles are associated with different colors of hair.
• The third statement: Alleles that only differ in the base sequence of regulatory elements can be associated with different phenotypes.
• The fourth statement: An allele can be defined by any difference—even a tiny one—in either the structural or regulatory segments of a gene.