Several amino acid substitutions in the α and β chains of human hemoglobin are shown in the following table.

Using the code table, determine how many of them can occur as a result of a single-nucleotide change.

Verified step by step guidance

1. Step 1: Identify the codons for the normal and substituted amino acids using the standard genetic code table. Each amino acid is encoded by one or more codons (triplets of nucleotides).
2. Step 2: For each hemoglobin variant, write down the codon(s) that could encode the normal amino acid and the codon(s) that could encode the substituted amino acid.
3. Step 3: Compare the codons for the normal and substituted amino acids to determine if the substitution can be caused by a single-nucleotide change. This means checking if changing one nucleotide in the normal codon can produce a codon for the substituted amino acid.
4. Step 4: Count how many of the amino acid substitutions in the table can be explained by a single-nucleotide change in the codon.
5. Step 5: Summarize your findings by stating the total number of substitutions that can occur due to a single-nucleotide change, based on your codon comparisons.

Key Concepts

Genetic Code and Codon Table

The genetic code consists of nucleotide triplets called codons, each specifying an amino acid. Understanding the codon table is essential to determine how a single-nucleotide change (point mutation) can alter a codon to code for a different amino acid, leading to amino acid substitutions in proteins.

Missense Mutations and Single-Nucleotide Changes

Missense mutations are point mutations where a single nucleotide change results in a codon that codes for a different amino acid. Identifying whether an amino acid substitution can arise from a single-nucleotide change requires comparing codons of the original and substituted amino acids.

Hemoglobin Structure and Variants

Hemoglobin is composed of α and β chains, each with specific amino acid sequences. Variants arise from amino acid substitutions in these chains, which can affect function. Understanding the location and nature of these substitutions helps relate genetic mutations to protein changes.