Cell Reproduction

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Cell Reproduction

• Mrs. Kirby

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DNA coils into Chromosomes
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• Double Stranded DNA wraps around proteins called
  histones
• Histones help to maintain the shape of a
  chromosome and aid in tight packaging of DNA.

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• After the DNA wraps around the proteins called
  histones it continues to coil more and more until
  it is supercoiled into a rod shaped structure
  called a Chromosome.

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The Structure of A Chromosome

• Consists of two identical halves called chromatids

• The two halves are joined by a centromere

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Reason For Chromosomes

• Chromosomes are formed so that cells can copy
  themelves quickly and efficiently.

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Two Types of Chromosomes

• Sex Chromosomes determine the sex of an organism
  
• In humans these are the X and Y chromosomes
• Autosomes All the non-sex chromosomes

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Karyotypes

• A library of the chromosomes in an organism
• Shows the chromosomes present in a cell
• Different organisms have different numbers of
  chromosomes
• Fruit fly 8 (4 pairs)
• Human 46 (23 pairs)
• Adders Tongue Fern 1,262 (631 pairs)

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Diploid vs. Haploid

• Cells with two sets of chromosomes are diploid
  (Diploid Cells are written as 2n)
• Cells with only one set of chromosomes are
  haploid (Hapliod cells are written as 1n)

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The Cell Cycle
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Parts of the Cell Cycle

• G1- Growth of Cell
• S- Copying of DNA
• G2- Growth and preparation for division
• M- Mitosis
• Cytokinesis- cytoplasm divides

Interphase
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Mitosis

• The division of the nucleus during cell division

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Four Phases of Mitosis

• Prophase
• Metaphase
• Anaphase
• Telophase

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Prophase

• Chromosomes condense, centrioles form, the
  nuclear envelope breaks down and spindle fibers
  begin to form and attach to the centromere (at
  the kinetochore)

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Metaphase

• Chromosomes line up at the middle of the cell

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Anaphase

• Chromatids separate at the centromere and start
  to move to oposite ends of the cell

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Telophase

• Spindle fibers break apart, centrioles disappear
  and the nuclear envelope reforms

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Cytokinesis

• The cytoplasm pinches inward until the cell
  splits in two.

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If a cell is not in the cell cycle

• It is in G0