Unit 4--Genetics

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Unit 4--Genetics

• Chapter 10
• Cell division

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Vocabulary of cell reproduction

• 1) Chromosomes
• Rod-shaped structure made of DNA coiled around
  protein
• 2) Gene
• Segment of DNA transmitting info about one trait
  (or one protein that controls that trait)

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• 3) Chromatids
• Two copies of each chromosome (after replication
  has occurred before separation)
• 4) Centromere
• Point of attachment between the chromatids
  (attaches to spindle fiber)

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Cell Cycle
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Mitosis

• Interphase
• Longest phase of a cells life cycle when the
  cell grows, maintains normal activity prepares
  to divide
• G1 growth in size
• S (synthesis) DNA replicates
• G2 duplication of other cell organelles

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• Prophase
• Chromatids shorten become visible
• Nuclear membrane nucleolus disappear
• Spindle fibers form
• (in animals) centrioles divide move to opposite
  poles
• Metaphase
• Chromatids line up along equator

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• Anaphase
• Chromosomes separate move to opposite poles
  (pulled by spindle)
• Telophase
• Chromosomes lengthen become invisible
• Nuclear mem nucleolus reappear
• Spindle breaks down

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• Cytokinesis occurs (actual division of
  cytoplasm)
• (in animals) cleavage furrow pinches membrane in
  two
• (in plants) cell plate forms to replace cell wall

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• Homologous C. (homologues)
• Chromosome pairs or mates (similar in size,
  shape, info)
• 0ne from each parent
• Humans have 23 pair (total 46)

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• Zygote
• (fertilized egg) first cell of an organism with a
  complete set of chromosomes
• Diploid (2n)
• Cell with a full set (two of each type) of
  chromosomes

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• Gametes
• Reproductive cells (eggs sperm)
• Haploid (n or 1n)
• A cell with one of each type of chromosome or
  half the total number

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Meiosis

• Production of haploid gametes
• Similarities to Mitosis
• Same basic stages, except occur twice

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• Differences
• Homologues remain together during prophase I
• Crossing over (when chromatids exchange pieces)
  occurs during metaphase I

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• Result is reduction division into 4 haploid
  cells instead of 2 diploids
• In males all 4 become sperm
• In females only 1 egg other polar bodies
  disintegrate