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Unformatted text preview: 107 Summary When Mendels principles were found to be widespread in application, scientists set out to discover what struc- tures within cells correspond to Mendels hypothetical units of heredity, which we now call genes. Recognizing that the behavior of chromosomes during meiosis paral- lels the behavior of genes, Sutton and Boveri suggested that genes were located in or on the chromosomes. Morgans evidence from sex-linked inheritance strength- ened the hypothesis. Proof that genes are on chromo- somes came from Bridgess use of aberrant chromosome behavior to explain inheritance anomalies. Chromosomes are distinguished by a number of topological features such as centromere and nucleolar position, size, and banding pattern. The stuff that chro- mosomes are made of is chromatin, composed of DNA and protein. Each chromosome is one DNA molecule wrapped around octamers of histone proteins. Between cell divisions, the chromosomes are in a relatively ex- tended state, although still associated with histones. Attended state, although still associated with histones....
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- Spring '08