Title: MEIOSIS
1MEIOSIS
2Review
- Homologous Chromosomes
- matching pair of chromosomes, one inherited from
each parent
3Review
- Somatic body cells, non sex cells, they are
diploid - Diploid or 2N having two sets of chromosomes
- Haploid or N having one set of chromosomes
4Diploid vs. Haploid Exercises
- Drosophilia have a diploid number of 8. What is
the haploid? - Onions have a haploid number of 8. What is the
2N? - A horses 2N is 64. What is the 1N?
- A body cell of an alligator has 32 chromosomes.
Is this the diploid or haploid number?
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16
32
Diploid
5II. Meiosis
- Definition
- cell division to produce egg (ovule) or sperm
(pollen)
6Karyotypes
- Display of chromosomes lined up in homologous
pairs - Half inherited from male Half from female
- Used for viewing , size, shape, and banding
- patterns of chromosomes
7- Autosomes 1-22
- Chromosomes that are not sex chromosomes
- Sex chromosomes 23
- Mammal females XX
- Mammal males Xy
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Moms Egg 23 chromosomes
Dads Sperm 23 chromosomes
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9- Fertilization
- when haploid sperm and egg
- meet, combining N chromosomes
- with N chromosomes
- 2N zygote
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- Zygote fertilized egg, 2N
10General Process of Meiosis
- MEIOSIS I (PMAT I C)
- - Prophase I homologous chromosomes meet up
- and form tetrads. Crossing over occurs.
11Process of Meiosis Con.t
- - Metaphase I homologous chromosomes line
up - along the equator the assortment among
- homologs is random
- - Anaphase I and Telophase I occur as usual
- - Cytokinesis splits cell in half.
- - Begins with one 2N gametocyte
- - Ends with two 1N cells
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20INDEPENDENT ASSORTMENT
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22CELL THEN GOES THROUGH INTERKINESIS- NO MORE
DOUBLING OF CHROMOSOMES!!
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24General Process of Meiosis
- MEIOSIS II (PMAT II C)
- - Starts with 2 haploid cells
- - Prophase, Metaphase, Anaphase, Telophase II
- and Cytokinesis serve to separate the
sister - chromatids
- - Ending Cells 4 cells, each with haploid
- chromosomes
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29Another Animation of Overall Meiosis
30Oogenesis Production of Egg
- Female meiosis in the ovaries
- Resulting cells
- 1 egg, 3 polar bodies
- Haploid
31SpermatogenesisProduction of Sperm
- Male meiosis in testes
- Resulting cells
- 4 haploid sperm cells
32Comparison between Spermatogenesis and Oogenesis
33What if Meiosis Did Not Use Haploid Cells?
- Every generation would inherit twice as many
- chromosomes
- Sperm (23) Egg (23) 46 chromosomes
- Sperm (46) Egg (46) 92 chromosomes
- Sperm (92) Egg (92) 184 chromosomes
34Why Meiosis increases Genetic Variation
- Assortment of Chromosomes
- Genetic Recombination (Crossing Over)
35Assortment of Chromosomes
36Crossing Over
Crossing Over can produce a single chromosome
that contains a NEQW Combination of genetic
information from different parents --- this is
GENETIC RECOMBINATION.
37- Mitosis
- Cell division
- 46 chromo?2 cells,
- 46 chromo. Each
- Keeps chromo. same
- Found in body cells
- Most common
- No genetic variation
- Meiosis
- Cell division
- 46 chromo? 4 cells,
- 23 chromo each
- Chromo. cut in half
- Found in sex/germ cells ONLY
- Least common
- Most genetic variation
ANIMATION OF COMPARISON
ANIMATION 2 OF COMPARISON