Lecture 6 - TA Andrew Nguyen office hours Change to 10-11am on Monday in the lobby of Price Center Theater Professor Zhang will have an office

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1 TA Andrew Nguyen office hours: Change to 10-11am on Monday in the lobby of Price Center Theater Professor Zhang will have an office hour (5:30-6:30 PM) tomorrow (April 16) in Rm 2250 of Cancer Center building (on the right side of the elevator on the second floor)
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2 Nondisjunction and Uniparental Disomy • Nondisjunction – failure of paired chromosomes to separate in anaphase of meiosis I, or failure of sister chromatids to disjoin at meiosis II. • Nondisjuction in meiosis produces gametes with 22 or 24 chromosomes. After fertilization by a normal gamate, form a trisomic or monosomic zygote, which are generally lethal and the embryo will be aborted. • Occasionally, one of the trisomy chromosomes is lost during the initial stage of embryo cell proliferation and development proceeds normally - trisomy rescue . • When the two rescued chromosomes are from the same parent, it is called uniparental disomy (UPD). • UPD is either heterodisomy (non-identical chromosome) or isodisomy (identical chromosome).
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3 Nondisjuction at meiosis I Nondisjuction at meiosis II A1 Trisomy
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4 Nondisjuction at meiosis I Nondisjuction at meiosis II lost A1A3 (lost another A1) A1A3 (lost A2) A2A3 (lost A1) Trisomy Rescue – UniParental Disomy (UPD) lost
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5 Nondisjuction at meiosis I Nondisjuction at meiosis II A1 lost heterodisomy isodisomy
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6 Uniparental Disomy (UPD) and Genomic Imprinting • If UPD chromosomes carry silenced imprinted genes, then, no functional gene product is made – developmental disorder. • If both UPD chromosomes carry active imprinted genes (the genes should be silenced from one parent of origin), the over production of these gene product may interfere normal development. • Therefore UPD can be a very serious problem and lead to abnormal development and cancer.
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7 Prader-Willi Syndrome 70% patients have a 3-5 Mb deletion at paternal 15q11-13 25% patients have maternal uniparental disomy of chromosome 15 Small deletions of 15q11-13 lead to silence of gene expression
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8 Molecular Basis of Human Disease BIMM 110 Spring 2010 Lecture 6 Germ cells, fertilization, and embryo development
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9
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10 Y chromosome absent Y chromosome present Paramesonephric duct Mesonephric duct (bipotential)
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11 Testis determining factor (TDF) is encoded by sex-determining region of the Y chromosome ( SRY )
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12 Genes involved in sex differentiation. Dysfunction of various genes can lead to abnormal gender differentiation.
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13
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Synthesis of androgens and estrogens. Enzyme mutations lead to a deficiency of androgens and estrogens. Deficiency of 17 -hydroxylase diverts precursors into the aldosterone pathway. Deficiency of 17 - hydroxysteroid dehydrogenase will change precursors to estrogens primarily as will a deficiency of  reductase. Female hormone
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This note was uploaded on 04/19/2010 for the course BIOLOGY BIMM110 taught by Professor Mcginnis during the Spring '10 term at UCSD.

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Lecture 6 - TA Andrew Nguyen office hours Change to 10-11am on Monday in the lobby of Price Center Theater Professor Zhang will have an office

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