BIOLecture2 - Outline for today’s lecture(Ch 13 •...

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Unformatted text preview: Outline for today’s lecture (Ch. 13) • Sexual and asexual life cycles • Meiosis • Origins of Genetic Variation – Independent assortment – Crossing over (“recombination”) Heredity • Transmission of traits between generations • Molecular basis of heredity is DNA replication • Gene is a specific segment of DNA • Physical location on the chromosome is called a genetic LOCUS (plural = “loci”) – e.g., the “eye-color locus”, Adh locus Asexual Life Cycles • Single (diploid) individual is the parent • Parent passes copies of ALL its genes to its offspring (reproduces “clonally”) • Various mechanisms – Mitotic cell division in unicellular Eukaryotes – Vegetative reproduction, e.g., plant cuttings, hydra budding – Parthenogenesis Sexual Life Cycles • Two (diploid) parents give rise to offspring • Offspring differ genetically from their parents and their siblings • GAMETES are haploid reproductive cells that transmit genes across generations Sexual Life Cycles • Key Point: Sexual reproduction → Genetic variation • MOST eukaryotes reproduce sexually at least sometimes • Most prokaryotes (e.g., bacteria) exchange genes at least occasionally Sexual Life Cycles – Human Example • 46 Chromosomes • 22 Homologous pairs, called “autosomes” – Same length – Same centromere position – Same sequence (+/-) – SAME GENES!! Sexual Life Cycles – Human Example • One pair of “sex chromosomes” – i.e., “sex-determining gene(s)” reside on these chromosomes • Females are XX • Males are XY • Only small region of homology (= same genes) between X, Y X Y Schematic drawing of a chromosome Diploid cell, n=3 BEFORE DNA replication • 3 Homologous Pairs...
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This note was uploaded on 07/03/2008 for the course BSC 2010 taught by Professor Bowes during the Spring '08 term at University of Florida.

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BIOLecture2 - Outline for today’s lecture(Ch 13 •...

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