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Page 1: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check
Page 2: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount

Why would you want to reduce chromosomes to half? (check with

your neighbor)

Page 3: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check
Page 4: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Egg = 23

Sperm = 23

Egg + Sperm = 46 in them.

If meiosis reduces the chromosome number

in half, how many chromosomes are in

human sex cells?

Page 5: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Haploid (n)– a half set of chromosomes

Diploid (2n) – a full set of chromosomes

Somatic Cells = ALL body cells (blood, skin, etc) except gametes

Page 6: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Gamete

Skin Cell

Egg

Somatic Cell

Sperm

Sex Cell

Haploid or Diploid?

Page 7: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Homologous Chromosomes – chromosomes that have the same

informationEx. Father/Paternal #11 chromosome

Mother/Maternal #11 chromosome

“Partner” up in Prophase 1

Page 8: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Crossing Over is the exchange of genetic material between homologous chromosomes

Crossing Over acts as a source of

genetic variation within a species

Page 9: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check
Page 10: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Stages of Meiosis•Interphase—1 time ONLY

– Growth and replication of DNA

• PMATC—2 times

– Prophase, Metaphase, Anaphase, Telophase, Cytokinesis

Page 11: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Diploid Cell—2 copies of each chromosome that replicated during

Interphase

Page 12: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Crossing Over occurred during Prophase 1

Page 13: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Anaphase AWAY

Page 14: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Telophase I/Cytokinesis results in 2 Haploid Cells

Page 15: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Prophase II looks similar to Telophase I, but nuclear envelope is

disappearing again

Page 16: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check
Page 17: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Anaphase Away—part II

Page 18: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Telophase II and Cytokineses results in 4 HAPLOID sex cells….or gametes….or egg….or

sperm!

Page 19: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check
Page 20: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check
Page 21: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

What’s different?

Page 22: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Egg (Ovum) is created in the Ovary

Page 23: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Sperm is created in the Testis

Page 24: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Diploid Numbers in other OrganismsName of Organism Diploid Number Image

Adders-tongueOphioglossum reticulatum

1440This fern has the highest known chromosome number of any life form

Field HorsetailEquisetum arvense 216

Red viscacha ratTympanoctomys barrerae

102 Highest number known in mammals, a tetraploid[3].

Hedgehog

90

Page 25: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Diploid Numbers in other OrganismsName of Organism Diploid Number Image

Turkey

80Dogs, Coyotes, Dingos, and Wolves 78

MuleHorse/Donkey Cross 63 *Infertile

Platypus 5210 Sex Chromosomes

Jack Jumper Ant 2 for females, 1 for males

Page 26: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Karyotype – a “map” of chromosomes

2 Main Uses:•Determine sex of the baby

•Screen for Chromosomal Abnormalities

Ex. Down Syndrome

Page 27: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

22 pair of Autosomes + 1 pair of sex chromosomes =23 Total pairs

XX = Female

XY = Male

Page 28: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check
Page 29: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check
Page 30: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Questions about Meiosis????

Page 31: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Quiz

• What are sex chromosomes called?

• How many chromosomes does a diploid cell have? Haploid?

• What is a karyotype used for?

Page 32: Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check

Quiz

• What is the purpose of crossing over?

• What does meiosis in male gametes create??

• What does meiosis female gametes create?


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