CHAPTER OVERVIEW S o far in our investigation of genetics, we have been concerned with processes that take place in individ-ual organisms and cells. How does the cell copy DNA, and what causes mutations? How do the mechanisms of segregation and recombination affect the kinds and pro-portions of gametes produced by an individual organ-ism? How is the development of an organism affected by the interactions between its DNA, the cell machinery of protein synthesis, cellular metabolic processes, and the external environment? But organisms do not live only as isolated individuals. They interact with one an-other in groups, populations, and there are questions about the genetic composition of those populations that cannot be answered only from a knowledge of the basic individual-level genetic processes. Why are the alleles of the protein Factor VIII and Factor IX genes that cause a failure of normal blood clotting, hemophilia, so rare in all human populations, whereas the allele of the hemo-globin b gene that causes sickle-cell anemia is very com-mon in some parts of Africa? What changes in the fre-quency of sickle-anemia are to be expected in the descendants of Africans in North America as a conse-quence of the change in environment and of the inter-
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.