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B. (10 pts) Taking data from the U.S. population in 1980, a newborn female had 9

ID: 61227 • Letter: B

Question

B. (10 pts) Taking data from the U.S. population in 1980, a newborn female had 98.7% chance of still being alive 5 years later, and a 60 year-old female had a 94.4% chance of surviving 5 years. Imagine a hypothetical population with these survival rates, and suppose that two different mutations appeared in the population that altered 5-year survival rates in different ways:

                                                5-year survival probability:

                                                age 0-5            age 60-65

original population                  0.987                  0.944

mutant A                                  0.993                  0.894

mutant B                                  0.990                  0.974

Assume that these mutations have no effect on health or fitness at any other ages. What will be the long-term outcome of natural selection on these mutations?

Explanation / Answer

* With mutation A, there is an increase in the survival rate after 5 years, but the survival after 60 years has reduced, the number of females that survive 5 years after 60 y age will be reduced. The decrease is 5%.

* With mutation B, the survival of 60 y age group for 5 more years increased by 3%.

* Overall, the surviaval chances of 60 y age group for 5 more years decreased by 2%, whereas the survival rate newborn is not much affected.

* Mutation A will be fixed by the natural selection.