Explain how a slightly deleterious allele that should be eliminated by weak negative selection might actually increase in frequency in a population
What will be an ideal response?
Ans: If the population is small in size, genetic drift (the random fluctuation of allele frequencies) may have a greater effect than selection. By chance, a variant that is weakly selected against may actually become more common.
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Non-disjunction is the failure of homologous chromosomes to separate during meiosis I, or the failure of sister chromatids to separate during meiosis II or mitosis. As a result, both homologous chromosomes or both sister chromatids migrate to the same pole of the cell. This produces daughter cells with an imbalance of chromosomes. A cell biologist examines the final products of meiosis in an earthworm (2n=36) and finds 2 cells with 20 chromosomes, and 2 cells with 16 chromosomes. Most likely this was because
A. 2 pairs of sister chromatids failed to separate during meiosis II. B. 1 pair of sister chromatids failed to separate during meiosis II. C. 2 pairs of homologous chromosomes failed to separate during meiosis I. D. 1 pair of homologous chromosomes failed to separate during meiosis I. Clarify Question · What is the key concept addressed by the question? · What type of thinking is required? · What key words does the question contain and what do they mean? Gather Content · What do you know about non-disjunction? How does it relate to the question? Consider Possibilities · What other information is related to the question? Which information is most useful? Choose Answer · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer? Reflect on Process · Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
While mapping two genes in Drosophila, you observe 30 recombinants among 200 total offspring. What is the distance between these genes?
A. 30 map units B. 6.67 map units C. 200 map units D. 15 map units
Methanogens often grow in association with
A. nitrifying bacteria. B. lithotrophic bacteria. C. photosynthetic bacteria. D. fermentative bacteria.
Most human embryos that are aneuploid
A. result in Down's syndrome. B. result in sterility. C. are spontaneously aborted in the first trimester. D. can develop and survive to adulthood. E. are usually the result of increased nondisjunction in the gametes of older men.