Question

A molecule that can be used as a molecular clock has a neutral mutation rate of one mutation per 5 million years. How many years ago did two species share a common ancestor if the molecules found in these two species differ by a total of eight mutations?
Answer







1.5 million years








10 million years








20 million years








40 million years

Answer 1

how would i solve this

Answer 2

40?

Answer 3

why a ?

Answer 4

The question is saying that a molecule starts out the same in two species that have just split. It says the molecule mutates (changes in some small way) once every 5 million years.
So, after 5 million years, you expect to see one change in the molecule. After 10 million years, you expect to see 2 changes. So, how long do you have to wait to see 8 changes?

Answer 5

5-1
10-2
15-3
20-4
25-5
30-6
35-7
40-8

Answer 6

The answer is 20 million years. I took this test 3 times and every time the answer was 20 million years! :)