Ch 15 cont and 16

Ch 15 cont and 16 - Chromosomal Alterations Two basic kinds...

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2/11/11 Chromosomal Alterations Two basic kinds a) Alterations of chromosome number b) Alterations of chromosome structure
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2/11/11 Change in Chromosome Number Aneuploidy = abnormal number of chromosomes per cell Caused by nondisjunction Homologous chromosomes (or sister chromatids) do not separate during meiosis One gamete receives both pairs, and another gamete receives none Picture 3 Picture 17 gametes from non-disj. meiosis gametes from normal meiosis Monosomic For Chr. 2 (1 copy) X X X Trisomic For Chr. 2 (3 copies) Diploi d Upon fertilization: Nondisjunction may occur frequently, but most aneuploid zygotes are spontaneously aborted
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2/11/11 Some human disorders are due to aneuploidy (If less upsetting to the genetic balance, embryos can survive) Picture 7 Nondisjunction of sex chromosomes Klinefelter syndrome : XXY; extra X in a male offspring 1/2000 Male sex organs, feminine body contours Normal intelligence Turner syndrome (Monosomy X): X0 only known monosomy in humans Rare (1/10,000) Phenotypically female Sterile, normal intelligence Triple-X: XXX not considered a disorder usually undiagnosed 5-10 tri-X girls born per day in US
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2/11/11 Change in chromosome structure Four types: 1. Deletion: Fragment of chromosome is missing Homozygous deletions usually lethal Ex. Cri-du-chat” Syndrome (Heterozygous deletion on chromosome 5) small head, unusual cry, mental retardation, usually die in infancy/childhood 1. Inversion : Fragment breaks off, reattaches to same place but backwards 1. Duplication: Fragment of one homolog breaks off and becomes attached to OTHER homolog. The sequence is 2x in one gamete. 1. Translocation: A segment is moved from one chromosome to another (not the same homologous pair)
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Click to edit Master subtitle style 2/11/11 Chapter 16 The Molecular Basis of Inheritance -DNA
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2/11/11 The Search for the Genetic Genetic (heritable) material was located on chromosomes Chromosomes made of DNA and protein, so either could be the heritable material Most thought protein, because DNA too “simple” Two lines of evidence suggested it was DNA: 1. Transformation experiments 2. Bacteriophage experiments
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This note was uploaded on 02/10/2011 for the course BIOL 101 taught by Professor Chattergee during the Fall '06 term at South Carolina.

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Ch 15 cont and 16 - Chromosomal Alterations Two basic kinds...

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