The wild-type allele of a gene has an A–T base pair at a particular location in its sequence, and a mutant allele of the same gene has a G–C base pair at the same location. Otherwise, the sequences of the two alleles are identical. Does this information tell you anything about the dominance relationship of the alleles? Explain why or why not.

Verified step by step guidance

1. Understand that dominance relationships between alleles refer to how the phenotype of heterozygotes compares to the phenotypes of homozygotes for each allele.
2. Recognize that the information given describes a single nucleotide difference (A–T in wild-type vs. G–C in mutant) but does not provide any data about the phenotypic effects of these alleles when present in heterozygous individuals.
3. Recall that dominance is determined by the functional effect of the alleles on the gene product and the resulting phenotype, not simply by the nucleotide sequence difference.
4. Note that without experimental data on the phenotype of heterozygotes or information about gene expression or protein function, the nucleotide difference alone cannot predict dominance.
5. Conclude that knowing only the base pair difference at a specific site does not provide enough information to determine the dominance relationship between the wild-type and mutant alleles.

Key Concepts

Alleles and Genetic Variation

Alleles are different versions of the same gene that arise due to variations in the DNA sequence. These variations, such as a single base pair change, can affect gene function or expression, but the presence of a mutation alone does not determine how alleles interact in terms of dominance.

Dominance Relationships

Dominance describes how one allele's trait masks or overrides the effect of another allele in a heterozygote. Whether an allele is dominant or recessive depends on the functional consequences of the genetic variation, not just the sequence difference itself.

Genotype-Phenotype Correlation

Understanding dominance requires linking genotype (DNA sequence) to phenotype (observable traits). A single base pair change may or may not alter the protein or its function, so without phenotypic data, the dominance relationship cannot be inferred solely from sequence differences.