The following graph shows a molecular clock for several pairs of organisms. The

Question

The following graph shows a molecular clock for several pairs of organisms. The

asterisks (*) represent the data for these pairs. The time of divergence of to humans based on fossil evidence is on the X axis and the sequence divergence (in number of base pair differences for a particular gene) compared to humans is on the Y axis.

Answer the following two questions.

4.4 There is an important species without fossil information and you want to know how long ago it diverged. You sequence the gene and find that it has 4 differences when compared to human. Using this rough molecular clock based on this gene

a. The species diverged 0.6 million years ago

b. The species diverged 1.6 million years ago

c. The species diverged 2.2 million years ago

d. The species diverged 2.4 million years ago

e. There is not enough information to answer the question.

4.5 A colleague hears that you have calibrated a molecular clock and she calls you telling you that she would like to use it to calibrate a divergence time using your molecular clock for a species she is interested in. She tell you that she has sequenced the species for the clock gene and the divergence of the sequence from human is 15 changes. You advise her against using your clock. Why?

a. Her species didn

Explanation / Answer

4.4 Answer: (e) There is not enough information to answer the question

The graphs shows that the sequence of divergence started < 2.8 millions to 0.8 million years ago. So, there is information or option provided to answer this question.

4.5 Answer: (d) The sequence divergence is too small to work with your clock

The given data is very small to work up on.

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