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Karyotypes & Genetic Disorders

Karyotypes & Genetic Disorders. Karyotypes. an organized profile of a person’s homologous chromosomes (somatic cells only) Each pair is organized by size, banding patterns, and location of centromere. Centromere. Banding Pattern. “Bands” are large segments of DNA

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Karyotypes & Genetic Disorders

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  1. Karyotypes&Genetic Disorders

  2. Karyotypes an organized profile of a person’s homologous chromosomes (somatic cells only) Each pair is organized by size, banding patterns, and location of centromere Centromere

  3. Banding Pattern “Bands” are large segments of DNA **Remember what chromosomes are made up of

  4. Exception: Position 23 Chromosome Pair #23 determines sex Only pair that might NOT match up… WHY? vs.

  5. Female 23rd pair of chromosomes are homologous Both chromosomes are “X” chromosomes

  6. Male 23rd pair of chromosomes are NOT homologous One chromosome is “X” and the other is a “Y” chromosome

  7. Normal Karyotypes Has 46 chromosomes for humans Arranged in 23 pairs

  8. Disjunction Normal separation of Chromosomes and Chromatids during Meiosis I and Meiosis II (Anaphase I & II)

  9. NON-disjunction Nondisjunction during Meiosis I Metaphase I Anaphase I Failure to separate homologous pairs

  10. NON-disjunction Nondisjunction during Meiosis II Metaphase II Failure to separate Chromatids Anaphase II

  11. What does nondisjunction cause? Missing Chromosomes – Monomy Embryo/Fetus will not survive Means 45 chromosomes Exception is this can occur on 23rd chromosome pair Extra Chromosomes – Trisomy Means 47 chromosomes • Down Syndrome (Trisomy 21) • Patau Syndrome (Trisomy 13) • Klinefelter’s Syndrome (XXY) • Turner’s Syndrome (X-) • XYY Syndrome • And many more………….

  12. Trisomy 21 – Down Syndrome Extra Chromosome 21

  13. Trisomy 13 – Patau Syndrome • Symptoms can include • Cleft lip or palate • Close-set eyes -- eyes may actually fuse together into one • Decreased muscle tone • Extra fingers or toes • Hernias • Hole, split, or cleft in the iris • Low-set ears • Mental retardation • Scalp defects (absent skin) • Seizures • Single palmar crease • Skeletal (limb) abnormalities • Small eyes • Small head • Small lower jaw • Undescended testicle Extra Chromosome 13

  14. Klinefelter’s Syndrome (XXY) Extra Sex Chromosome “X”

  15. Turner’s Syndrome (X-)

  16. XYY Syndrome • XYY syndrome is characterized by an extra copy of the Y chromosome • males with this condition may be taller than average • This chromosomal change typically causes no unusual physical features • Most males with XYY syndrome have normal sexual development and are able to father children

  17. Jamie Lee Curtis • XY male with Androgen Insensitivity Syndrome (AIS) • resistant to androgens • the hormones responsible for male sexual development

  18. QUESTIONS???

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