Question

what is a point mutation?
○ a nucleotide is substituted in a gene sequence, which alters the associated codon.
○ an amino acid is inserted in a protein chain, which alters all subsequent amino acids.
○ an amino acid is inserted in a protein chain, which may alter protein function.
○ a codon is deleted from a gene sequence, which alters all subsequent nucleotides.
○ a codon is inserted in an mrna strand, which alters all subsequent codons.

Explanation:

A point mutation is a type of genetic mutation where a single nucleotide base in the DNA sequence (gene sequence) is changed (substituted). This substitution can lead to a change in the corresponding codon (a triplet of nucleotides in mRNA that codes for an amino acid).

• Option B and C are incorrect as point mutations occur at the nucleotide level in the gene, not at the amino - acid level in the protein chain.
• Option D and E are incorrect as they describe frameshift mutations (insertion or deletion of a nucleotide or codon that shifts the reading frame and affects all subsequent nucleotides/codons), not point mutations.

Answer:

A. A nucleotide is substituted in a gene sequence, which alters the associated codon.