Wk 4 Lec 20

Wk 4 Lec 20 - Whatwerewetalkingabout? Homologouschromosomes

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What were we talking about? Homologous chromosomes Sexual reproduction Meiosis Meiosis I Meiosis II Sources of variation
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Mistakes in Meiosis
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Preparing a Karyotype A karyotype is a photographic inventory of an individual’s  chromosomes. Blood samples are cultured for several days under  conditions that promote cell division of white  blood cells. NOTE: Red blood cells lack nuclei and do not divide. The culture is treated with a chemical that stops cell  division at metaphase. White blood cells are separated, stained, and squashed in an effort to spread out the  chromosomes.
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Preparing a Karyotype The individual chromosomes in a photograph are cut out and rearranged  by number.  The ordered display of chromosomes is called a karyotype From this the genetic sex of an individual can be determined and  abnormalities in chromosomal structure and number can be detected.
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Connection: An extra copy of chromosome 21 causes Down syndrome. In most cases, human offspring that  develop from zygotes with an incorrect  number of chromosomes abort  spontaneously. Trisomy 21 is the most common 
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Wk 4 Lec 20 - Whatwerewetalkingabout? Homologouschromosomes

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