Some recessive mutations can be exceedingly debilitating or lethal when expressed in homozygotes. If their effects are so severe, why doesn't natural selection simply purge such alleles from the population completely?
What will be an ideal response?
Natural selection does act on these alleles when they are expressed, but for the most part, when alleles are rare they occur in heterozygotes and are thus masked. Another reason selection cannot eliminate such alleles completely is that they arise continually by mutation. Finally, any recessive alleles that are expressed late in life will be shielded from natural selection, since they will not affect an individual's chances of producing viable offspring.
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Which of the following is not a eukaryotic retrotransposon?
A. gypsy B. Ty elements C. LINEs D. SINEs E. Tc1/mariner
You are working in a research lab on the organism Drosophila melanogaster and you have been given the job of
determining the relative positions of three linked genes for your undergraduate research project. A graduate student in the lab tells you that gene a is 5.0 centimorgans from gene b, and that gene c is 2.7 centimorgans from gene b. What should you do to finish mapping these three genes? What are the likely results that may occur, and how would you interpret such results?
What will be an ideal response?Compare and contrast the structure and functions of three of the following four intercellular junctions:desmosomes
, gap junctions, tight junctions, and plasmodesmata. What will be an ideal response?
Genetics is defined as the study of:
A. cells B. DNA C. heredity D. traits E. chromosome behavior