Reduction-Division Genetic Recombination 1

cell division GAMETES, HALF CHROMOSOMES,  The form of cell division by which GAMETES, with HALF the number of CHROMOSOMES, are produced.  DIPLOID (2n)  HAPLOID (n)  MeiosisSEXUAL reproduction.  Meiosis is SEXUAL reproduction.  TWO divisionsMEIOSIS I MEIOSIS II  TWO divisions (MEIOSIS I and MEIOSIS II). 2

GAMETES(sperm or egg)  Sex cells divide to produce GAMETES (sperm or egg). HALF  Gametes have HALF the # of chromosomes. 3

2n=46 human sex cell diploid (2n) 2n=46 Meiosis I n=23 sperm haploid (n) Meiosis II 4

mitosis  Similar to mitosis interphase.  CHROMOSOMES (DNA)  CHROMOSOMES (DNA) replicate chromosometwo identical SISTER CHROMATIDS CENTROMERES  Each duplicated chromosome consist of two identical SISTER CHROMATIDS attached at their CENTROMERES.  ONLY  ONLY occurs during meiosis I 5

 Cell division chromosome number one- half.  Cell division that reduces the chromosome number by one- half.  Cell division  Cell division in which chromosomes go though same stages as mitosis.  Four phases  Four phases: a.Prophase I b.Metaphase I c.Anaphase I d.Telophase I 6 Prophase I

Homologous pairs of chromosomes separate 7 Meiosis I Chromosome #3 (two copies)

Sister Chromatids Separate 8 Meiosis II

 No Interphase II  No DNA Replication  Four phases to divide sister chromatids. 9

 Remember: FOUR HAPLOID DAUGHTER cells are produced.  Called GAMETES (eggs and sperm) 10 1n Sperm cell fertilizes 1n egg to form 2n zygote

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