Tuesday Dec' 5th

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Tuesday Dec. 5th

• Test tomorrow! Review session tomorrow morning
• Packet is due tomorrow. Every problem must be
  completed and packets will be graded for
  correctness
• Any for GIVE A THON?

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Agenda

• Karyotypes
• Errors in Meiosis
• Im my own grandpa
• Work on packet
• Homework due Wednesday
• Packet page 26-27 34-37
• packet page 28-29 38-42
• Read text pages 122-123 (including box) - ON TEST

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Karyotype

• Diagram showing images of a complete set of
  chromosomes from an individual
• Each chromosome has an homologous (identical)
  chromosome
• One chromosome of the homologous pair comes from
  the fathers sperm and one chromosome of the
  homologous pair comes from the mothers egg
• Allows us to look for several thousand possible
  genetic diseases in humans

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How do scientists make karyotype?

• Before a cell begins to divide, its chromosomes
  are a tangled mass in the nucleus
• When cell division begins, the chromosomes become
  more tightly packed and can be seen easily with a
  microscope
• Scientists use a chemical to stop cell division
• Scientists add another chemical that causes
  nucleus of each cell to swell and burst.
• The cells are put on a slide and stained. Each
  pair of chromosomes will have a different banding
  pattern
• Scientists take picture of stained chromosomes.

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What are the two types of chromosomes?(2)
Based on the karyotype, how can you tell if it is
a boy or girl?(3) In human karyotype how
many chromosomes should you see? How many
homologous pairs of chromosomes?
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Males are XY, females are XX. It is possible
for individuals to be XXX, XXXY, XXY, X, XYY

• During which type of cell division do you think
  the error occurred?

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Non-Disjunction

• When chromosomes dont separate equally to create
  haploid cells
• Can occur with any chromosome and results in an
  unusual chromosome called polyploidy
• Monoploidy- only 1 chromosome of homologous pair
  in zygote
• Triploidy- 3 copies of homologes in zygote

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Normal Meiosis (spermatogenesis or oogenesis)
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Error in meiosis Non-disjunction in first
division
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Error in meiosis Non-disjunction during second
division
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Watch trisomy animation
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People with extra sex chromosomes are sterile

• Non-disjunction of sex chromosomes, can cause
  syndromes such as..
• XXY- Kleinfelter syndrome
• X - Turner syndrome
• XYY - super man
• XXX- super woman

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Kleinfelter Syndrome

• Occurs in 1 in 500 to 1 in 1000 births
• Develop as males but are tall and do not develop
  secondary sex characteristics such as facial and
  underarm hair

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Turner Syndrome

• Occurs 1 in 2000 to 1 in 2500 briths
• Short stature, lack of ovarian development
• Webbed neck and arms that turn slightly at the
  elbow

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Which syndrome does this karyotype show?
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Which syndrome does this karyotype show?
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When chromosomes dont separate equally in the
other chromosomes, the autosomes

• If there are 3 copies of chromosome 21, then
  individual will develop DOWN SYNDROME

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Karyotype of Down Syndrome