Question
A high number of alleles (80% ) present in thoroughbred race horses can be traced back to a small number of horses from the 1700's. Therefore, we would expect __ ? a. Abnormally low rates of mutation b. Little varitaion for selection in the present day c. High amounts of random mating d. No evolution over that time period
Solution
4
(314 Votes)
Nigel
Master ยท Tutor for 5 years
Answer
The correct answer is **b. Little variation for selection in the present day.**Here's why:* **Genetic Bottleneck:** The fact that 80% of alleles trace back to a small number of horses indicates a genetic bottleneck. A bottleneck drastically reduces the genetic diversity of a population. Even as the population grows again, much of the original variation is lost.* **Selection and Variation:** Natural selection acts upon existing variation. With limited variation, there is less opportunity for selection to differentiate between individuals and drive evolutionary change. This doesn't mean evolution *stops*, but it does mean the *rate* of evolution likely slows down considerably, especially for traits linked to those alleles.Let's look at why the other options are incorrect:* **a. Abnormally low rates of mutation:** Mutation rates are generally constant for a given species. While a bottleneck can *indirectly* influence which mutations become fixed in a population, it doesn't directly change the underlying mutation rate.* **c. High amounts of random mating:** The passage doesn't provide information about mating patterns. While random mating can *maintain* existing variation, it doesn't create new variation. Given the bottleneck, even with random mating, the overall variation would still be low.* **d. No evolution over that time period:** Evolution is an ongoing process. Even with reduced variation, some evolution will still occur through mutation, genetic drift, and any selection that can act on the remaining variation. However, the *rate* of evolution is likely to be slower.