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Meiosis & Genetics

Meiosis & Genetics. Sexual Cell Reproduction Ch. 10.2. Genetics. The Study of Inherited Characteristics. Chromosome. DNA Code for traits. X. Genes on chromosomes :. Hair Color. Segments of DNA on a chromosome Code for a trait. X. Eye Color. Gene Segment For Hair color.

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Meiosis & Genetics

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  1. Meiosis & Genetics Sexual Cell Reproduction Ch. 10.2

  2. Genetics The Study of Inherited Characteristics

  3. Chromosome DNA Code for traits X

  4. Genes on chromosomes: Hair Color • Segments of DNA on a chromosome • Code for a trait X Eye Color

  5. Gene Segment For Hair color

  6. Trait • Characteristic • Feature • Variations in a population

  7. Chromosome Number Homologous Chromosomes are the sets of each pair • Different # for different species • Full set = 2N=Diploid • N= • # pairs • 1 pair from mother • 1 pair from father • Humans= 23 pairs or • 46 total

  8. Autosomes & Sex Chromosomes Autosomes = # 1-22 for all traits except sex Sex chromosomes= Pair # 23 XX(female) or XY(male)

  9. Why do cells divide by Meiosis? Sperm • To reduce chromosome number • In sex cells • Or in single celled organisms: • Under changing conditions for • Chromosome Variety N egg N 2N baby

  10. Gonads make gametes! Testes make sperm

  11. Gonads make gametes! Ovaries make eggs

  12. Gamete develoment • Imature egg or sperm cell = full set of chromosome (2N) • Undergoes meiosis with 2 cell divisions • Develops into a mature egg or sperm (1N) 2N 1N

  13. Meiosis in the Gonads Sperm Meiotic cell division Egg

  14. Interphase Prophase I Metaphase I Anaphase I Telophase I Prophase II Metaphase II Anaphase II Final Telophase Full set of chromosomes (2N) DNA has doubled (4N) 1st cell division (2N) DNA does not double 2nd division Sperm & Egg (1N) 2nd division (1N) Stages in Meiosis:

  15. Meiotic Cells…….. Immature Egg or sperm 2N • Divide twice to • 1/2 Chromosome number • “Haploid” • Sperm or eggs 4N 2N 2N 1N 1N 1N 1N

  16. Genetic Recombination • Variety in chromosomes from • Crossing over = • Exchange of parts • Of Homologous chromosomes B A X X B A

  17. Trisomy=gamete with 3 of one type Monosomy=gamete with 1 of one type Tripoidy= zygote with three of one type 2N Nondysjunction = chromosomes fail to “dis-join” or separate: 2N Eggs forming 2nd division 2N empty 1N 1N + 2N egg 3N = 1N sperm

  18. Down Syndrome= 3 of #21

  19. Klinefelter’s = XXY

  20. Turner’s Syndrome • XO sex chromosome • Instead of XX female • Or XY for male: XO X + Empty sperm =

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