Jan. 25 - A bit of basic biology What is a gene? Where are...

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1 A bit of basic biology • What is a gene? • Where are genes carried? • Where are chromosomes found? Chromosomes are found in the nucleus of the cell – Nucleus – ―cell‖ within a cell that holds the genetic material • Every cell in the body (with a nucleus) has complete set of chromosomes Command Central Diploid – Every cell has a pair—two copies—of gene • One from your mother • One from your father – The genes from the two copies interact to produce YOU • Humans have 23 pairs of chromosomes – 22 pairs of autosomal chromosomes – 1 pair of sex chromosomes Your blueprint(s)
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2 Human karyotype Half as much is just as good • The gametes (reproductive cells) are haploid – they have just one copy of the individual’s genome – Why? • One complete set of autosomes and one of the sex chromosomes—either X or Y • Human females are XX – So every egg has the X • Human males are XY – Sperm could be X or Y Back to the Bug Diploid, Haploid • Many insects have sexual reproduction, and all offspring are diploid • Many insects have same pattern – XX = female – XY = male • Many Lepidoptera have reverse pattern – XX = male – XY = female
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3 Haplodiploidy : • Females come from fertilized eggs: – XX • Males come from unfertilized eggs: – X0 • Seen in Hymenoptera – Honey bees – Parasitic wasps Bee careful • When a queen honey bee lays an egg, she senses the size of the cell as she backs into it • Small cells, she fertilizes – These larvae will be haploid or diploid? – Gender? • Large cells, she doesn’t fertilize – These larvae will be haploid or diploid? – Gender? Sex vs. no sex Parthenogenesis • Asexual reproduction – eggs develop without fertilization (no sperm) – Aphids – mostly female • Female XX – diploid • Male XO – diploid but one sex chromosome lost – Some black flies – Some weevils – Honey bees – all female • Male XO - haploid
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Jan. 25 - A bit of basic biology What is a gene? Where are...

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