Karyotyping and Disorders Due to Nondisjunction

1. Karyotyping and Disorders Due to Nondisjunction Chapter 15 B and Chapter 13 – Fig. 13.3

2. What is a karyotype? • Ordered displays of individual’s chromosomes, paired by homologues • Chromosomes arranged from largest to smallest • Autosomes arranged first • Homologues according to centromere position • Sex chromosomes = last pair

6. How is a karyotype prepared? • Obtain cells (usually lymphocytes) • Treat cells w/ drug • Stimulate mitosis • Treat cells w/ different drug • Cease at metaphase • Chromosomes at highest condensed state • Centrifuge, Lyse cells, Fixative added, Centrifuge • Stained, viewed Pg: 237

7. Giemsa Staining • One type of dye for chromosomes • Stains at A-T regions of DNA • Thinnest band can contain hundreds of genes • Dyed regions called “G-bands” • Landmarks for describing loci of other genes

8. Why are karyotypes useful? • ID chromosomal mutations • Deletions and Duplications • Inversions • Translocations • ID abnormal # of chromosomes in fetus • Down, Edward’s, • Turner’s, Klinefelter’s • Are these the reasons why stillborn? • ID sex of child using • Male/Female • Are chromosome defects reason for miscarriages/prevention of pregnancy

9. Useful cont’d • Past evolutionary events • Taxonomic relationships • Cellular functions • Some types of cancer

11. Polyploidy vs. Aneuploidy • Polyploidy – abnormal # of complete SETS of chromosomes (n) • Triploidy – 3n • Tetraploidy – 4n • Remember: humans normal – 2n • Aneuploidy – abnormal chromosome # • Trisomy – 3 copies of chromosome X • Monosomy – 1 copy of chromosome X

12. What causes these? • Nondisjunction – • Failure of homologue separation in meiosis I • Failure of chromatid separation in meiosis II • Result of Nondisjunction? • Gamete contains • 2 of same copy of chromosome • No copy of chromosome

14. Turner’s (AKA Monosomy X) • Population affected: • Females • Karyotype: • 45, X, Monosomy X • How did this occur? • Nondisjunction during meiosis I or II; ovum or sperm did not have X chromosome • Anatomical/Physiological differences: • Sterile; usually normal intelligence; usually need estrogen replacement therapy

15. Klinefelter’s • Population affected: • Karyotype: • How did this occur? • Anatomical/Physiological differences:

16. Supermale/Superfemale • Population affected: • Karyotype: • How did this occur? • Anatomical/Physiological differences:

17. Down • Population affected: • Karyotype: • How did this occur? • Anatomical/Physiological differences:

18. Chronic Myelogenous Leukemia (CML) • Population affected: • Karyotype: • How did this occur? • Anatomical/Physiological differences:

19. Edward’s • Population affected: • Karyotype: • How did this occur? • Anatomical/Physiological differences:

20. Patau • Population affected: • Karyotype: • How did this occur? • Anatomical/Physiological differences:

21. Cri du chat • Population affected: • Karyotype: • How did this occur? • Anatomical/Physiological differences:

22. Fragile X Syndrome • Population affected: • Karyotype: • How did this occur? • Anatomical/Physiological differences:

23. Klinefelter’s • Population affected: • Males • Karyotype: • 47, XXY • How did this occur? • Nondisjunction during meiosis I or II; ovum or sperm having both sex chromosomes • Anatomical/Physiological differences: • Sterile; small testes; various feminine body characteristics (i.e. enlarged breasts); usually normal intelligence

24. Supermale/Superfemale • Population affected: • male/female • Karyotype: • 47, XYY • 47, XXX (Trisomy X) • How did this occur? • Nondisjunction during meiosis I or II; ovum or sperm having both sex chromosomes fuse with ovum/sperm with normal # of sex chromosome • Anatomical/Physiological differences: • Male: usually taller (some ppl think that they have increased rage tendency • Female: healthy, just like normal female

25. Down • Population affected: • Any – usually children born to family that mom is older that 35 • Karyotype: • 47, XX or 47, XY (Trisomy 21) • How did this occur? • Nondisjunction during meiosis I or II; ovum or sperm having an extra copy of #21 fuses with normal gamete • Anatomical/Physiological differences: • Various degrees of mental retardation; short; facial features (almond eyes, round face); heart defects; respiratory infections

26. Chronic Myelogenous Leukemia (CML) • Population affected: • Any human • Karyotype: • Translocation of chromosomes 22 and 9 • How did this occur? • Sections of non-homologous chromosomes 22 and 9 switch places • Anatomical/Physiological differences: • Cancer – leukemia – white blood cells

27. Edward’s • Population affected: • Any – male/female • Karyotype: • 47, XX or 47 XY (Trisomy 18) • How did this occur? • Nondisjunction during meiosis I or II; ovum or sperm having an extra copy of #18 fuses with normal gamete • Anatomical/Physiological differences: • Death by a few months of birth

28. Patau • Population affected: • Any – male/female • Karyotype: • 47, XX or 47 XY (Trisomy 13) • How did this occur? • Nondisjunction during meiosis I or II; ovum or sperm having an extra copy of #18 fuses with normal gamete • Anatomical/Physiological differences: • Polydactyly; small head (microcephaly); metal retardation; cardio defects

29. Cri du chat • Population affected: • Any – male/female • Karyotype: • 46, XX or 46 XY (Specific deletion in chromosome 5) • How did this occur? • Section of chromosome 5 was not copied during synthesis, was “deleted” • Anatomical/Physiological differences: • Mental retardation; microcephaly; certain facial features; cries like a cat mewing; usually death during infancy/early years of life

30. Fragile X Syndrome • Population affected: • Any, male/female • Karyotype: • 46, XX or 46, XY • How did this occur? • One of the X chromosomes stays together only by a thin edge of DNA • Anatomical/Physiological differences: • Mental retardation