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MEIOSIS

S x. MEIOSIS. Cell Reproduction. Meiosis. The form of cell division by which gametes (Sex cells), with half the number of chromosomes, are produced. Diploid (2n)  haploid (n) Meiosis is used for sexual reproduction.

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MEIOSIS

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  1. S x MEIOSIS Cell Reproduction

  2. Meiosis • The form of cell divisionby which gametes (Sex cells), with half the number of chromosomes,are produced. • Diploid (2n)  haploid (n) • Meiosis is used for sexual reproduction. • Two divisions (meiosis I and meiosis II) 4 cells are produced at the end of meiosis. 100 % of original DNA 50 % of original DNA

  3. n=23 human sex cell sperm n=23 n=23 2n=46 haploid (n) n=23 n=23 diploid (2n) n=23 meiosis I meiosis II

  4. sperm n=23 n=23 egg 2n=46 zygote Fertilization • The fusion of a sperm and egg to form a zygote. • A zygote is a fertilized egg

  5. Homologous Chromosomes • Pair of chromosomes (mother’s and father’s) that are similar in shape and size. • Homologous pairs carry genes controlling the same inherited traits (eye color, hair color, nose shape, etc.) • Humans have 23 pairs of homologous chromosomes (46 total chromosomes) a. 22 pairs of autosomes (body structures) b. 1 pair of sex chromosomes (Determine gender)

  6. eye color eye color hair color hair color Paternal Maternal Homologous Chromosomes

  7. Humans have 23 Sets of Homologous ChromosomesEach Homologous set is made up of 2 Homologues. Homologue Homologue

  8. Sex Chromosomes In Humans the “Sex Chromosomes” are the 23rd set XX chromosome - female XY chromosome - male

  9. Crossing Over • Crossing over (variation) may occur between chromosomes. • Crossing over: pieces of nonsisterchromatids break and reattach to the other chromatid.

  10. Tetrad nonsister chromatids chiasmata: site of crossing over Crossing Over = variation variation

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