Lecture Notes 20

Lecture Notes 20 - Lecture 20 3/27/2008 Biosc 0350 Genetics...

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Lecture 20 3/27/2008 1 Biosc 0350 Genetics Lecture 20 - Prokaryotic chromosomes and genetic analysis Chromsomal mutations Changes in chromosome number - aneuploidy Introduction to bacteria How do we observe bacteria What are common bacterial phenotypes Genetic transfer in bacteria Conjugation vs transduction F factor and Hfr strains Gene mapping - time of entry (low resolution) - recombination frequency (high resolution) 3/27/08 Martens. Biosc 0350, University of Pittsburgh 2 Changes in chromosome number } Polyploidy
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Lecture 20 3/27/2008 2 3/27/08 Martens. Biosc 0350, University of Pittsburgh 3 Nondisjunction during meiosis Note: only the chromosome displaying abnormal behaviour is shown Disjunction : normal segregation of homologous chromosomes or chromatids Nondisjunction is more likely to occur in Meiosis I Why? Hartwell et al., 3rd ed. Figure 14.32 3/27/08 Martens. Biosc 0350, University of Pittsburgh 4 Monosomics Monosomics of any human autosome is lethal in utero XO is viable - Turner syndrome
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Lecture 20 3/27/2008 3 3/27/08 Martens. Biosc 0350, University of Pittsburgh 5 Trisomics In humans, most trisomics are lethal in utero except: XXY (Klinefelter syndrome) XYY (phenotypically normal) XXX (phenotypically normal) Trisomy 21 (Down syndrome) - mean life expectancy 17 years Trisomy 18 (Edwards syndrome) - mean life expectancy ~ weeks Trisomy 13 (Patau syndrom) - mean life expectancy 4 months Consequences of trisomic chromosomes = 3/27/08 Martens. Biosc 0350, University of Pittsburgh 6 In class problem#2 2) A couple has a phenotypically normal son who, upon inspection of his sex chromosomes, is found to be XYY. In what parent, and in what meiotic division, could the nondisjunction causing this constitution have happened? Male - the nondisjunction yielding a zygote with two Y chromosomes could only come from a YY sperm. X Y First division Second division Second meiotic division. Nondisjunction at the first division will yield disomic sperm. They will be XY, not YY.
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Lecture 20 3/27/2008 4 3/27/08 Martens. Biosc 0350, University of Pittsburgh 7 http://www.cdc.gov/ncidod/eid/vol8no5/01-0385-G1.htm part of one cell of intestinal brush border epithelium, thin section, electron micrograph cross-section of the middle of an E. coli bacterium (arrowhead points to one edge). length of the bacterium
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This note was uploaded on 04/07/2008 for the course BIOSC 0350 taught by Professor Josephmartens during the Spring '08 term at Pittsburgh.

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Lecture Notes 20 - Lecture 20 3/27/2008 Biosc 0350 Genetics...

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