Lecture 21 Bio325 Fall 07

Lecture 21 Bio325 Fall 07 - 1 Changes in chromosome number:...

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Unformatted text preview: 1 Changes in chromosome number: rare events that occur during abnormal meiotic or mitotic segregation Table 14.1 Aneuploidy: loss or gain of one or more chromosomes such that the chromosome number is not an exact multiple of the haploid number Aneuploidy usually occurs because of nondisjunction- a failure to segregate chromosomes correctly during either meiosis I or meiosis II: Fig. 14.32 2 Example: An organism with the genotype AaBb undergoes meiosis and generates a rare gamete with the genotype aBb. This probably occurred by nondisjunction in which phase of meiosis? A. meiosis I B. meiosis II C. could have been either meiosis I or meiosis II D. could not have occurred in either meiosis I or meiosis II Nondisjunction involving the X chromosome in Drosophila: Fig. 4.21 Table 4.1 3 A Klinefelter male has the genotype XXY What nondisjunction events (in either meiosis I or II, and in either the mother or the father of the Klinefelter male) could give rise to this genotype? If you know that the Klinefelter male has 2 copies of the same X chromosome, which non-disjunction must have been responsible?...
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This note was uploaded on 06/19/2008 for the course BIO 325 taught by Professor Saxena during the Fall '08 term at University of Texas at Austin.

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Lecture 21 Bio325 Fall 07 - 1 Changes in chromosome number:...

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