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Unformatted text preview: 482 Chapter 15 Large-Scale Chromosomal Changes CHAPTER OVERVIEW A young couple is planning to have children. The hus- band knows that his grandmother had a child with Down syndrome by a second marriage. Down syndrome is a set of physical and mental disorders caused by the presence of an extra chromosome 21 (Figure 15-1). No records of the birth, which occurred early in the twenti- eth century, are available, but the couple knows of no other cases of Down syndrome in their families. The couple has heard that Down syndrome results from a rare chance mistake in egg production and there- fore decide that they stand only a low chance of having such a child. They decide to have children. Their first child is unaffected, but the next conception aborts spon- taneously (a miscarriage), and their second child is born with Down syndrome. Was this a coincidence, or is it possible that there is a connection between the genetic makeup of the man and that of his grandmother that led to their both having Down syndrome children? Was theto their both having Down syndrome children?...
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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.
- Spring '08