Question

Suppose that every human gamete contains approximately 40,000 genes.

a. If the forward mutation rate is 1 × 10‐5 new mutations per gene per
generation, what is the average number of new mutations per gamete per
generation? Show your work.

b. What is the average number of new mutations per gamete per generation if
the forward mutation rate is 1×10‐4? Show your work.

Answer 1

A. If the rate of mutation is $10^{-5}$ per gene, it means that mutation occurs once in every 100 000 genes. There are approximately 40,000 genes in every human gamete. We can write the number of genes as a ratio:

```

40 000 : 100 000

2 : 5

```

It means that 5 gametes would be contain 2 new mutations. In other words, 2 out of 5 gametes would be contain a newly arisen mutation.

B. If the rate of mutation is $10^{-4}$ per gene, it means that mutation occurs once in every 10 000 genes. The ratio is:

```

40 000 : 10 000

4 : 1

```

It means that each gamete would be contain at least 4 new mutations.