BIOLecture2 - Outline for todays lecture (Ch. 13) Sexual...

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Unformatted text preview: Outline for todays 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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BIOLecture2 - Outline for todays lecture (Ch. 13) Sexual...

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