Prior to the 1960s most evolutionary biologists did not expect natural populatio
ID: 35743 • Letter: P
Question
Prior to the 1960s most evolutionary biologists did not expect natural populations to harbor much genetic variation, because they assumed genetic variation would be removed from a population by natural selection. However, molecular work that began in the late 1960s showed that most natural populations harbor a substantial amount of genetic variation. (i) Describe two hypotheses or theories that have been proposed to account for this observation. (ii) What predictions does each hypothesis or theory make? (iii) Describe an experiment that could be used to evaluate the relative support for these two hypothesis or theories in a specific species or population. (iv) Use a table or graph to summarize results that would be consistent with one these hypotheses but not the other. Make sure to indicate which hypothesis your hypothetical results support. (13 points)Explanation / Answer
In the mid-1960s laboratory techniques such as electrophoresis and selective assay of enzymes came into the picture and became available for the rapid and inexpensive study of differences among enzymes and other proteins. The application of these techniques to certain evolutionary problems prevailing at that time made possible the pursuit of issues that earlier could not be investigated at all.For example, exploring the extent of genetic variation occuring in natural populations which seemed to sets bounds on their evolutionary potential and determining the amount of genetic change that occurs during the formation of still newer species.
Comparisons of the amino acid sequences of corresponding proteins in and among different species provided quantitatively a precise measure of the divergence noticed among species evolved that from common ancestors, a considerable improvement over this typically qualitative evaluation was obtained by comparative the anatomy and other evolutionary subdisciplines.
scientists proposed the neutrality theory of molecular evolution, which assumes that, at the basic level of the sequences of nucleotides in DNA and of amino acids in proteins, many changes in general are adaptively neutral. That is, they have little or no effect on the molecule
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