Cytogenetics.txt

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kepling
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56020
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Cytogenetics.txt
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2010-12-14 19:35:56
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Cytogenetics
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Cytogenetics
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  1. What is cytogenetics?
    The study of diseases related to chromosomal abnormalities
  2. What is the leading cause of pregnancy miscarriage?
    Chromosome abnormalities
  3. In what stage are chromosomes viewed for cytokenetic studies?
    Metaphase - Mitosis
  4. What is the difference b/t metacentric, submetacentric and acrocentric chromosomes?
    • Metacentric: centromere at center
    • Submetacentric: centromere farther from center
    • Acrocentric: centromere closer to telomere near end where p-arm is really short
  5. What are the four values of utilizing FISH?
    • 1) microdeletions
    • 2) gene amplification
    • 3) abnormal karyotype detection
    • 4) cancer studies
  6. What is Polyploidy?
    Gain of one or more chromosome sets
  7. What is aneuploidy and what are two results of it?
    • Aneuploidy: gain or loss of one chromosome
    • Result: trisomy or monosomy
  8. What causes aneuploidy?
    Dysjunction at Meiosis I or II
  9. Are monosomies lethal or viable?
    Lethal
  10. What are the three viable trisomy chromosomes?
    13, 18, 21
  11. What is the disease related to Trisomy 21 and what are its symptoms (3)?
    • Disease: Down Syndrome
    • Symptoms: distinct face, GI problems, Heart defects
  12. At what age does the incidence of Trisomy 21 increase?
    >35 (although more incidences happen at younger ages just because more babies are born at this time)
  13. What is the disease associated with Trisomy 18 and what are its symptoms (6)?
    • Disease: Edward Syndrome
    • Symptoms: low weight, mental retardation, clenched fist, overlapping fingers, small eyes, omphlaocele (gut opened)
  14. What is the disease associated with Trisomy 13 and what are its symptoms (3)?
    • Disease: Patau Syndrome
    • Syndrome: cleft palate, postaxial polydactyly, large, triangular nose
  15. What type of disease is Turner syndrome and what are its symptoms (2)?
    • Monosomy, 45 XO
    • symptoms: webbed neck, short stature
  16. What is klinefelter syndrome and what are its symptoms (4)?
    • Trisomy, 47 XXY
    • Symptoms: tall, sterile, gynecomastia, small testes
  17. Why is the SRY gene important?
    It is what makes a male a true male. It is found on the Y chromosome
  18. How does an XX male form?
    The SRY gene is crossed during synapse of the pseudoautosomal region onto the X chromosome
  19. How does and XY Female form?
    The SRY gene is crossed over to the X chromosome and the Y is passed on to the female
  20. What is translocation?
    exchange of genetic material between non-homologous chromosomes
  21. How does a reciprocal translocation occur?
    Two parts of two chromosomes break and fuse with the other chromosome (3 with 6 and 6 with 3)
  22. What are the percentages of offspring when a reciprocal translocation occurs?
    • 25% normal
    • 25% gen. abnormal, phen. normal
    • 50% gen/pen abnormal
  23. What is unique about a Robertsonian translocation compared to a reciprocal?
    Robertsonian:Only on acrocentric chromosomes (centromere by telomere at small p-arm)
  24. What is the karyotype count for a Roberstonian trans.?
    45, b/c they lose two short arms and gain one long arm
  25. What is the chance of a robertsonian mother bearing a down syndrome child?
    1/6
  26. What are the three types of chromosomal deletions (TIR)?
    • 1) Terminal
    • 2) Interstitial
    • 3) Ring
  27. What is a terminal deletion ?
    single break and loss of one end of the chromosome
  28. What is an interstitial deletion?
    break at two places in an arm and fusion of the blunt ends
  29. What is a ring deletion?
    Two broken tips that cause the chromosome to fuse in ring form
  30. What are the two types of inversions?
    • 1) Pericentric: involving the centromere
    • 2) Paracentric: not involving the centromere
    • ***when they come together the cut pieces flip before inserting
  31. What is PKU?
    • Autosomal recessive disease
    • Lack of phenylalanine hydroxylase
    • phenylalanine builds up and is also converted to an acid
    • these cause neuronal damage
  32. What type of disease is Tay-Sachs and what population receives it most often?
    • Autosomal recessive (HEX A)
    • Ashkenazi Jews
  33. How does Preimplantation genetic diagnosis (PGD) work?
    • Have to be invitro fertilized
    • one of the 8 cells removed for testing of Tay-Sachs or other heterozygote diseases
  34. What are the four methods for prenatal screening and what part do they test?
    • 1) CVS- fetal tissue
    • 2) NTU- maternal blood/visual
    • 3) Amniocentesis- amniotic fluid
    • 4) ultrasound - visual
  35. What does a high AFP and a low AFP tell about a fetus?
    • High: risk for Neural Tube defect (NTD)
    • Low: risk for trisomy
  36. What two prenatal tests can be used for NTD and Trisomy?
    NTU and Amniocentesis
  37. At what weeks should the four tests be performed?
    • 1) CVS 9-12 wks
    • 2) NTU 11-14 wks
    • 3) Amniocentesis 15-17 wks
    • 4) anytime
  38. When should a triple screen be performed?
    15-20 wks
  39. What is extra in a quadruple test?
    inhibin-A (to help measure down syndrome)
  40. What are the three main enzymes tested in triple/quadruple test?
    • 1) MSAFP
    • 2) hCG
    • 3) Estriol

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