Meosis

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  • Topic: Stem cell, Developmental biology, Cellular differentiation
  • Pages : 3 (639 words )
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  • Published : February 4, 2013
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MEIOSIS
We study Gametes through a Karyotype
Each pair is called a homologous pair
Diploid= 23 pairs of chromosomes and 46 total chromosomes (2n) Haploid= 23 individual pairs
Mitosis- makes body cells, or asexual reproduction like cloning Meiosis- makes sex cells
Crossing Over- Occurs in Prohpase I
- each group of 4 chromatids are called a tetrad.
Individual chromatids may wrap around eachother and pieces may break off and reattach to other chromatids. Genes on chromosomes may change places. Causes recombiant chromosomes= get new arrangements of genes This creates variation in offspring.

Look at pictures
Independent assortment- random separation of the homologous chromosomes. This results in genetic variation. Crossing Over- Portions of chromatids may break off and attach to other chromatids. Random Fertilization- Not knowing which egg the sperm with fertilize. STEM CELLS

A stem cell is a cell whose job in the body isn’t determined yet. Differentiate- gradually change into the destined cell type
Protein Products cause the stem cell to differentiate.
Skin- as they differentiate they move closer to the surface
Bone- they are construction workers
Nerve- these cells are made before birth
Skeletal Muscle Cell- cells made by myoblasts
Red blood cell- made by bone marrow

TOTIPOTENT STEM CELLS- (totipotent)- total power, cell that can become any cell. Zygote- fertilized egg

Morula- solid ball of 16 cells

1-4 days for cell division
1-16 number of cells

PLURIPOTENT STEM CELLS- (pluripotent)- cell that can become several cell types

Blastula/Blastocyst- Hollow ball of cells with inner cell mass 4-14 days for cell division
100’s of cells

Embryonic stem cell- cells from the inner cell mass growing in a culture Made by destroying blastula and removing inner cell mass.
Most debatable and easy to grow
Embryonic Stem Cell line- cultures of cells that came from 1 blastula Embryonic and adult stem cells both come from nature, and have...
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