If a base-pair change occurs in DNA, this a. is a mutation. b. would be a mutation only if it falls in a protein-coding part of a gene. c. would be a mutation only if it falls in a transcribed part of the genome. d. is not a mutation, because only one base pair has been altered.

Verified step by step guidance

1. Understand the definition of a mutation: A mutation is any change in the nucleotide sequence of DNA, regardless of where it occurs in the genome.
2. Recognize that a base-pair change in DNA qualifies as a mutation because it alters the genetic material, even if only one base pair is affected.
3. Clarify that mutations can occur anywhere in the genome, not just in protein-coding or transcribed regions. However, the impact of the mutation may vary depending on its location.
4. Evaluate the options provided in the question: Option (a) correctly identifies that a base-pair change is a mutation. Options (b), (c), and (d) incorrectly limit the definition of a mutation or dismiss the change entirely.
5. Conclude that the correct answer is (a), as a base-pair change in DNA is universally considered a mutation, regardless of its location or functional significance.

Key Concepts

Mutation

A mutation is a permanent alteration in the DNA sequence that makes up a gene. Mutations can occur due to various factors, including environmental influences or errors during DNA replication. They can affect a single base pair or larger segments of DNA, and their consequences can range from benign to significant, potentially leading to diseases or phenotypic changes.

Protein-Coding Genes

Protein-coding genes are segments of DNA that contain the instructions for synthesizing proteins. These genes are transcribed into messenger RNA (mRNA), which is then translated into a specific protein. Mutations in protein-coding regions can lead to changes in the amino acid sequence of proteins, potentially altering their function and impacting the organism's phenotype.

Transcription and Transcribed Regions

Transcription is the process by which the information in a gene's DNA is copied into mRNA. Transcribed regions include not only protein-coding sequences but also non-coding regions that may play regulatory roles. Mutations in these areas can influence gene expression and function, even if they do not directly alter the protein product.