2320 Lecture 5 Sex Determination and Patterns of Inheritance NOTES.pptx

2320 Lecture 5 Sex Determination and Patterns of Inheritance NOTES.pptx

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χ 2 , Sex Determination and Sex-linked inheritance
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Outline Sex determination Sex chromosomes Sex-linked inheritance Abnormalities Dosage compensation Pedigrees
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commons.wikimedia.org engineerpal.com
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Sex determination – the mechanism (usually genetic) which determines the gender of an individual. In most animals, and many plants, sex is determined by number and type of sex chromosomes. In humans, females have two X chromosomes and males have one X and one Y chromosome . Females can only produce gametes with X chromosome – homogametic . Males produce ½ gametes with X, and ½ with Y chromosomes – heterogametic . Sex determination - chromosomes
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The X and Y chromosomes have only a few homologous regions (pseudoautosomal regions), most regions are different The Y chromosome contains only a few dozen genes. The SRY gene (sex determining region on Y) within the non- homologous region of the Y chromosome determines “maleness” – codes for the “testis determining factor” (TDF) . Genes located in the non-homologous regions show sex linked inheritance patterns – either X-linked or Y-linked . Sex determination - chromosomes
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Sex determination - chromosomes Fig 2-15 Homologous pseudoautosomal regions allow X-Y pairing during meiosis I 
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There are many different chromosome-based sex determining mechanisms: Sex determination - chromosomes Humans, Drosophila Many insects, C. elegans Birds Bees, Wasps
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Like humans, male Drosophila have XY and females have XX.
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  • Spring '12
  • TBA
  • Genetics, Sex linkage, X chromosome, Y chromosome, Turner syndrome

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