Chromosomes

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Chromosomes The Cell Cycle
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Chromatin Chromosome Composition

• Made of
• DNA
• Protein - histones
• Chromosome Structure (after replication)
• 2 chromatids identical chromosomes
• centromere holds sister chromatids together
• p and q arms

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Chromosome Structure
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Chromosome Numbers Types

• Each species has characteristic number
• Humans 46
• Chimpanzee 48
• Fruit fly 8
• Two Types
• Sex chromosome
• Humans 2
• XX female
• XY male
• Autosome (body chromosome)
• Humans 44
• 22 from each parent
• Matching chromosomes homologous chromosomes
• (one from mom and one from dad)

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Karyotype

• Photograph of chromosomes in dividing cell.
• Taken during metaphase
• -Like chromosomes are lined up next to each other.

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Chromosomes and Cells

• Diploid Cell
• 2 sets of chromosomes one from dad and one from
  mom
• 2 sex chromosomes
• Body cells (somatic)
• Haploid Cells
• 1 set of chromosomes
• 1 sex chromosome
• Sex cells
• Egg
• Sperm

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Cell Division Prokaryotes

• -prokaryotes have cell walls but no nucleus and
  membrane bound organelles.
• -have a single DNA molecule, circular chromosome
  attached to the cell membrane.
• -examples bacteria
• -cell division is called binary fission.

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Binary Fission

• -results in two new identical cells.

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Cell Division Eukaryotes

• -cytoplasm and nucleus divides.
• -two types of cell division in eukaryotes,
  mitosis and meiosis.
• -Mitosis results in the production of two new
  identical cells containing a full set of DNA
  material.
• -Meiosis results in the formation of gametes
  containing one half the DNA material.

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The Cell Cycle

• Interphase
• G1
• S
• G2
• G0
• Cell Division Mitosis
• Prophase
• Metaphase
• Anaphase
• Telophase
• Cytokinesis

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Stages of Mitosis
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Final Details Control of Cell Division

• 1. G1 checkpoint proteins control whether or
  not the cell will divide and whether or not DNA
  synthesis can proceed.
• 2. G2 checkpoint DNA repair enzymes check the
  newly replicated DNA.
• 3. Mitosis checkpoint if all is good, proteins
  signal for mitosis to end and cells enter G1.
• The proteins that control cell division are coded
  for by genes. If the gene is mutated, the
  proteins may be altered. This may lead to cancer.