Question

The molecular clock model assumes that mutation rates are:

• A. equal for all genes.
• B. constant for a gene.
• C. variable across geographical regions.
• D. variable across geological time.

Hint:

To understand the molecular clock model:
1. Recognize that it assumes a constant mutation rate for specific genes.
2. Remember that different genes can evolve at different rates depending on their function and selective pressures.
3. Use this model to estimate divergence times between species by comparing genetic sequences.

Answer 1

The Correct Option is B

Step 1: Understand the molecular clock model. The molecular clock hypothesis is based on the assumption that mutations in DNA or protein sequences occur at a relatively constant rate for a specific gene. This regularity allows scientists to estimate the time of divergence between two species or lineages by comparing genetic differences. Step 2: Evaluate the options. Option (A): Mutation rates being equal for all genes is incorrect because different genes can evolve at different rates due to varying selective pressures and functions. Option (B): Mutation rates being constant for a specific gene is correct. This is the fundamental assumption of the molecular clock model, enabling time estimation based on genetic variation. Option (C): Mutation rates being variable across geographical regions is unrelated to the molecular clock model, as it focuses on genetic sequences rather than geographical factors. Option (D): Mutation rates being variable across geological time contradicts the assumption of a constant mutation rate for a gene.