Chromosome Number

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Meiosis and Mitosis
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What is Mitosis for?

• 1. Reproduction in favorable conditions.
• 2. Growth and Development
• 3. Tissue repair and cell replacement
• If an organism had the ability to reproduce
  sexually or asexually, which would they choose?

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• This is NOT mitosis, what is it?

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G2 check point
G1 check point
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• 90 of cells are___
• Whatif less than 90?
• What is Cancer?

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• What if a cell in G1 of interphase were fused
  with a cell in metaphase?

• G2 check-point
• Cyclin
• Cdk
• MPF ?

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MITOSIS What phase is this cell most likely
in?How many chromosomes? Would you see chromatin
here? How many centromeres? How many sister
chromatids? Draw this cell in Anaphase. How many
kinetochores? How many spindle fibers will it
take to move all of the chromosomes during
metaphase and anaphase? What is the 2n number for
this cell?What is the n number for this cell?
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How many chromosomes? How many chromatids? What
do the blue lines represent? What are they made
of? The Kinetochores are very important here
because In which phase do spindle fibers start
attaching to the kinetochores? In which specific
phases (or parts of phases) will you find sister
chromatids?
Anaphase
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What phase of mitosis? Is this animal or
plant? What is this process called? And in a
plant, how is it different?
Is this DNA in the chromosome or chromatin phase?
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Chromosome Number
Homologous Chromosomes are the pairs

• Different for different species
• Full set 2nDiploid
• n
• full set 46 in humans
• 1 pair from mother, 23
• 1 pair from father, 23
• Humans 23 pairs or
• 46 total

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Autosomes Sex Chromosomes
Autosomes 1-22 for all traits except sex
Sex chromosomes Pair 23 XX(female)
or XY(male) XXX? XXY? XYY? X?
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Meiotic Cells..
Immature Egg or Sperm still in the gonads
2n

• Divide twice to
• 1/2 chromosome numberWHY?
• Haploid n
• Sperm or eggs only

2n doubled DNA Xs
Meiosis I PMAT
2n
2n
Meiosis II PMAT
n
n
n
n
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• How many differences can you come up with between
  meiosis and mitosis?
• 2 stages (PMAT,PMAT)
• 4 daughter cells formed
• Crossing over (when?)
• Random assortment
• 2 different metaphases
• Not clones
• Haploid (not diploid)

MEIOSIS ?
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• What is the longest phase of meiosis? why?
• What is synapsis? Chiasmata or chiasma?What is a
  tetrad?
• What is so important about what has happened
  here?

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I

• Check out Metaphase I II, what is different?
• What is the 2n number of this species?
• What is the n number?

II
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• What might this cell look like in prophase I?
• in metaphase I of meiosis?
• in prophase II?
• What might each daughter cell look like after
  meiosis II?
• Is there a different daughter cell outcome that
  could have happened?
• What would each daughter cell look like after
  mitosis?

2n ____
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p.230

• 2n n Alternate 2n nanimals
  fungi, algae plants, algae

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KARYOTYPEDown Syndrome 3 of 21
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Klinefelters XXY
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• LAB 3A, pages 31-40 will be due in about 1 ½
  weeks (around 10/25). We will hand in 3A with 3B
  when it is complete.
• Start now!