Lect 17 - 1 Chromosomal Basis of Disease Bio Sci 97 Lecture...

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©2003 C. Brachmann 1 Chromosomal Basis of Disease Bio Sci 97 Lecture 17 Dr. Carrie Brachmann Department of Developmental and Cell Biology cbrachma@uci.edu Reading, lect 18 and 19:  HJ: Ch4.1, 4.2, 4.3  Gist: Ch9 D and E, good review: Gist Ch 4
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©2003 C. Brachmann 2 Lecture 16 Answers T/F All of the gametes produced by an individual are genetically identical to somatic cells of that individual. False
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©2003 C. Brachmann 3 = dense, compact Label the stained metaphase chromosome below: 4pt In which region are most genes found? telomere centromere heterochromatin euchromatin euchromatin
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©2003 C. Brachmann 4 Outline Dosage compensation Polyploidy Polysomy Nondisjunction Aneuploidy
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©2003 C. Brachmann 5 So, females have two X chromosomes and  males have only one. Does this give females an advantage? No, in fact, too much of a good thing is  BAD…
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©2003 C. Brachmann 6 X-inactivation and dosage compensation Dosage compensation adjusts the activity of X-linked genes in females to equal that in males In females, one X chrm is inactivated in each SOMATIC cell The inactive X chrm becomes highly heterochromatic and is called a Barr body (see H&J, section 5.1 for more info)
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©2003 C. Brachmann 7 Fig. 5.7 H&J An X chrm that is  inactivated in a  particular somatic cell  remains so in all  descendants
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©2003 C. Brachmann Females are genetic  mosaics for X-linked genes The X chrm that is active differs from one cell to the next==> genetic mosaic (contains cells of two or more different genotypes) Examples: calico cat (female het for org and black) sweat glands (female het for sweat glands) ocular albinism (female het for retinal melanin) QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. 6
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©2003 C. Brachmann 9 Review of human chromosome complement Somatic cells are diploid 46 chromosomes 22 pairs of autosomes 1 pair of sex chrms (XX or XY) Gametes are haploid 23 chromosomes 22 autosomes 1 sex chromosome (X or Y)
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©2003 C. Brachmann 10 A human  karyotype : blood cells arrested in metaphase are  stained with Giemsa and photographed with a microscope
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©2003 C. Brachmann 11 Abnormal numbers of chromosomes Diploid Tetraploid 4n Decaploid 10n Polyploid Euploid an exact multiple of the monoploid # "balanced" Trisomy
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This note was uploaded on 04/15/2008 for the course BIO SCI 98 taught by Professor Goulding during the Spring '08 term at UC Irvine.

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Lect 17 - 1 Chromosomal Basis of Disease Bio Sci 97 Lecture...

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