The two DNA and polypeptide sequences shown are for alleles at a hypothetical locus that produce different polypeptides, both five amino acids long. In each case, the lower DNA strand is the template strand: allele A₁ 5′. . . ATGCATGTAAGTGCATGA. . . 3′ 3′. . . TACGTACATTCACGTACT. . . 5′ A₁ polypeptide N–Met–His–Val–Ser–Ala–C allele A₂ 5′. . . ATGCAAGTAAGTGCATGA . . . 3′ 3′. . . TACGTTCATTCACGTACT . . . 5′ A₂ polypeptide. N–Met–Gln–Val–Ser–Ala–C Based on DNA and polypeptide sequences alone, is there any way to determine which allele is dominant and which is recessive? Why or why not?

Key Concepts

Alleles and Dominance

Alleles are different versions of a gene that arise by mutation and are found at the same place on a chromosome. Dominance refers to the relationship between alleles, where one allele can mask the expression of another. In genetics, a dominant allele will express its trait even in the presence of a recessive allele, while a recessive allele only expresses its trait when paired with another recessive allele.

Transcription and Translation

Transcription is the process by which the DNA sequence of a gene is copied into messenger RNA (mRNA), which then undergoes translation to synthesize polypeptides (proteins). The sequence of nucleotides in DNA determines the sequence of amino acids in a polypeptide, which ultimately influences the protein's function. Understanding these processes is crucial for analyzing how genetic information is expressed.

Phenotypic Expression

Phenotypic expression refers to the observable traits or characteristics of an organism, which result from the interaction of its genotype (the genetic makeup) with the environment. In the context of alleles, the phenotype can be influenced by whether an allele is dominant or recessive. However, without additional information about the functional effects of the polypeptides produced by the alleles, it is not possible to determine dominance solely from the sequences provided.