Cell Reproduction Mitosis

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Cell Reproduction Mitosis
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Chromosomes

• Made of DNA
• Wrap around histone proteins to become chromatin

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Chromosomes

• Chromatin wind up further to become chromosomes
• Each half of a chromosome is a chromatid
• Chromatids are held together in the center at the
  centromere

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Chromosomes

• Sex chromosomes determine an organisms sex
• Females XX
• Males XY
• Number of sex chromosomes in a human cell is 2

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Chromosomes

• Autosomes all the chromosomes except for the
  sex chromosomes
• Number of autosomes in humans 44

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Chromosomes

• Homologous chromosomes every cell in sexual
  organisms has two copies of each autosome

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Chromosomes

• Humans have 44 autosomes so they have 22
  homologous pairs.
• Dogs have 76 autosomes so they have 38 homologous
  pairs.
• Goat 58
• Armidillo 62
• Chicken 78
• House fly 12
• Mosquito 6

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Diploid

• Cells with 2 sets of chromosomes (homologous
  prs.) are diploid.
• In humans, the diploid number is 46 (2n)

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Haploid

• Cells with one set of chromosomes are haploid.
• In humans, the haploid number is 23 (1n).

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Cell Division -Prokaryotes

• Bacteria do not have a nucleus.
• They divided by a process known as binary fission.

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Binary Fission

• Chromosomes replicate
• The cell grows to twice its original size
• The cell divides into two identical cells

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Cell Division in Eukaryotes

• Eukaryotes have a nucleus in their cells
• Mitosis results in new cells with identical
  genetic material
• Meiosis results in new cells with half the
  number of chromosomes

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Cell Cycle

• Set of events that make up the life of a cell

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Interphase

• Takes up most of the cells lifespan (up to 90)

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Interphase

• G1 phase cell grows to mature size
• S phase DNA replication
• G2 phase cell prepares for division

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Mitotic Phase

• Series of events that allows a cell to divide
• Prophase
• Metaphase
• Anaphase
• Telophase

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Prophase

• DNA winds up into chromosomes
• Centrioles appear at opposite ends of the nucleus

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Prophase

• Spindle fibers form
• Chromosomes attach to spindle fibers
• Nuclear membrane and nucleolus disappear

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Metaphase

• Chromosomes move to the center (equator) of the
  cell

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Anaphase

• Chromatids separate by the centromere
• They are now considered to be individual
  chromosomes

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Telophase

• Spindle fibers disappear
• Chromosomes begin to unwind into chromatin
• Nuclear membranes begin to form

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Cytokinesis

• Immediately follows mitotic division
• The cell membrane is split in half

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Animal Cytokinesis

• The membrane pinches off into two new cells

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Plant Cytokinesis

• A cell plate forms in the center.
• The plate separates the two cells.