sex - Sex Determination and Sex Linkage Sex and Sex...

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• Sex and Sex Determination – Chromosomal – Single gene – environment • Sex Chromosomes – XY, XX and WW, WZ systems – Dosage compensation • Sex linkage • Chromosomal theory of inheritance • Imprinting Sex Determination and Sex Linkage Which sex are you? Dioecious species (two houses) separate sexes – How is sex determined? – Most (but not all) animals are dioecious – Many plants are also dioecious Monoecious species (hermaphrodites) – Many plants are monoecious (both seed and pollen producers) – Some animals are hermaphrodites • Example: One genus of Arizona lizards are exclusively female. How is sex determined? • Chromosome-based systems – Differentiated (morphologically-different) sex chromosomes -- mammals, many other animals – Undifferentiated sex chromosomes (many plants, a number of animals) • Single-gene based systems – Example: Yeast mating type – Common for unicellular species • Environment sex determination – Egg temperature in some turtles – Sex switching in reef fish Sex chromosomes vs. autosomes Autosomes : Each homologous pair consists of two morphologically-identical chromosomes Sex chromosomes : The chromosome types contributed by mom and dad are different (X from mom, Y from dad)
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Homogametic vs. Heterogametic sex • Homogametic sex Sex containing two like sex chromosomes Most animals: females ( XX ) Butterflies and Birds, snakes, others: males ( ZZ ) • Heterogametic sex Sex containing two unlike sex chromosomes Most animals: males ( XY ) Some insects have XO males (only one sex chromosome) Butterflies and Birds, etc: : females ( ZW ) Mammalian X and Y • The X chromosome is gene-rich • Very few genes on the Y • Pseudoautosomal regions on Y – Contain same genes as in X – Hence, appear as if autosomal – Important in X:Y pairing in male meiosis Humans A few plants also have differentiated X/Y sex chromosomes
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Systems of sex determination
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This note was uploaded on 09/17/2009 for the course ECOL 320 taught by Professor Weinert during the Spring '07 term at University of Arizona- Tucson.

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sex - Sex Determination and Sex Linkage Sex and Sex...

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