Transcript Meiosis Powerpoint

Why do some scientist feel that
diarrhea is hereditary?
It runs in our
“genes”/jeans
Cell Cycle including Meiosis
(known as Gametogenesis)
Purpose:
To create germ cells, gametes or sex cells.
- cells with ½ the number of chromosomes
- known as 1N cells
-two types of germ cells
-sperm
-egg / ova
-in humans 1N/monoploid # =23
-contains 1 chromosome from each of the
23 pairs.
Two types of gametes
Spermatogenesis:
-meiosis that takes place in the testicles
-produces sperm
-made starting at puberty and ends at
death
-occurs everyday at a rate of 120 to
200 million/day
Male Reproduction
Oogenesis:
-meiosis that takes place in the ovaries
-produces ova/eggs
-occurs:
-during 2nd month of fetal development
-ova stored and released once a month
during menstrual cycle -starting at
puberty and ending with menopause
-each ovary contain approximately 300,000
eggs.
Female Reproductive
Gametogenesis
1 parent cell divides twice creating four
cells with ½ the number of chromosomes.
Parent cell is either a testicle or an ovary
cells each starting with 46 chromosomes.
Meiosis I
Meiosis II
Interphase I
Occurs in testicle or ovary cell, 2N cells
DNA replicates
Prophase I
1.
2.
3.
4.
Chromatin supercoils into chromatid
Centrioles split and form spindle fibers
Nucleus and nucleolus disassemble
Homologous pairs of chromosomes pair up
Homologous Chromosomes
Chromosomes
that carry the
same set of
genes.
One is from
your mom and
one from your
dad.
Metaphase I
1. Homologous pairs of chromosomes move
to the middle of the cells, each pair lines
up on one spindle fiber.
2. Chromosomes line up randomly
Anaphase I
1. Homologous pairs of chromosomes split
apart and move away to opposite sides of
the cell.
2. Asters push against cell membrane
causing the cell to elongate.
Telophase I with cytokinesis
1. Nucleus and nucleolus reform
2. Cell divides into two/cytokinesis
3. End result is now 2 cells each with 23
replicated chromosomes each.
Interphase II
DNA does not replicate
The rest of meiosis II is identical to
mitosis.
End result is four cells each with ½ the number
of chromosomes.
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