Abnormal Meiosis

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4.4

• Abnormal Meiosis
• Nondisjunction Disorders

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Lets review some genetics terms
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Genetics Terms

• Our body cells are also known as
• A. somatic cells
• B. gametes

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Genetics Terms

• Our body cells are also known as
• A. somatic cells
• B. gametes

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Genetics Terms

• Sperm and egg cells are
• A. somatic cells
• B. gametes

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Genetics Terms

• Sperm and egg cells are
• A. somatic cells
• B. gametes

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Genetics Terms

• Examples of human somatic cells are
• A. skin cells, bone cells, nerve cells
• B. sperm cells, egg cells

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Genetics Terms

• Examples of human somatic cells are
• A. skin cells, bone cells, nerve cells
• B. sperm cells, egg cells

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Genetics Terms

• Somatic cells are diploid, which means
• They divide very quickly.
• They have two sets of chromosomes.
• They have one set of chromosomes.

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Genetics Terms

• Somatic cells are diploid, which means
• They divide very quickly.
• They have two sets of chromosomes.
• They have one set of chromosomes.

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Genetics Terms

• Which of the following is true?
• Gametes are haploid.
• Gametes are diploid.
• Gametes are reproductive cells.
• Two of the above are true.

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Genetics Terms

• Which of the following is true?
• Gametes are haploid.
• Gametes are diploid.
• Gametes are reproductive cells.
• Two of the above are true.

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Genetics Terms

• Which of the following is true?
• Homologous chromosomes
• A. are similar in size and shape
• B. are found in gametes
• C. are found in somatic cells
• D. separate during Anaphase II
• E. Two of the above are true.

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Genetics Terms

• Which of the following is true?
• Homologous chromosomes
• A. are similar in size and shape
• B. are found in gametes
• C. are found in somatic cells
• D. separate during Anaphase II
• E. Two of the above are true.

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Now lets look at meiosis again
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What kinds of errors can happen during meiosis?
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Non-disjunction

• can happen during Anaphase I or during Anaphase
  II
• results in gametes with too many or too few
  chromosomes
• can also happen in mitosis, but less harmful
  because not passed on to the next generation

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Chromosomal Disorders

• wrong number of chromosomes
• or
• changes (mutations) in the genetic information

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Karyotype - male or female?
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Karyotype - male or female?
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Down syndrome (trisomy 21)
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Down Syndrome

• about 1 in 800 babies
• varying degrees of intellectual disability
• characteristic facial features
• often have heart defects other problems

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Trisomy 13
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Trisomy 18
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Trisomy 13 Trisomy 18

• 1 in 16000 babies born with trisomy 13 and 1 in
  5000 born with trisomy 18
• severe intellectual disabilities
• many physical birth defects
• most affected babies die before their first
  birthday

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Klinefelter syndrome
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Klinefelter syndrome

• about 1 in 500-1000 boys
• usually normal intelligence but many have
  learning problems
• as adults produce less than normal amounts of
  testosterone are infertile

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Turner syndrome
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Turner syndrome (monosomy 23)

• 1 in 2500 girls
• usually infertile do not undergo normal puberty
  changes unless treated with hormones
• some have health problems including heart and
  kidney defects
• normal intelligence but some have learning
  difficulties

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Triple X
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Triple X

• 1 in 1000 females
• usually no physical birth defects
• experience normal puberty are fertile
• usually normal intelligence but many have
  learning problems

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XYY
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XYY

• 1 in 1000 males
• sometimes taller than average
• have normal sexual development are fertile
• most have normal intelligence some have
  learning, behavioral and speech/language problems

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Assisted Reproductive Technologies (ARTs)
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ARTs

• in vitro fertilization (IVF)
• artificial insemination

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Applications Implications

• animal breeding
• wildlife conservation
• many benefits to using artificial insemination
• cost?