1 / 28

Nondisjunction

Nondisjunction. A. Failure to separate homologous chromosomes during Meiosis. 1. nondisjunction leads to aneuploidy. 2. nondisjunction of autosomal chromosomes:. a. monosomics. 2. nondisjunction of autosomal chromosomes:. b. trisomics. if one of the 5 smaller ones, somewhat viable.

inez-leblanc
Download Presentation

Nondisjunction

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Nondisjunction A. Failure to separate homologous chromosomes during Meiosis

  2. 1. nondisjunction leads to aneuploidy

  3. 2. nondisjunction of autosomal chromosomes: a. monosomics

  4. 2. nondisjunction of autosomal chromosomes: b. trisomics

  5. if one of the 5 smaller ones, somewhat viable 13, 15, 18, 21, 22

  6. trisomy 21 and 22 may be survivable into adulthood

  7. 3. nondisjunction of sex chromosomes:

  8. Klinefelter syndrome: XXY

  9. Turner syndrome: XO

  10. YY gametes (sperm)  XYY

  11. XX gametes  XXX

  12. OY  not viable

  13. Mutations A. Random changes in genes 1. rare 2. usually recessive

  14. B. Hemophilia - loss of any of 12 clotting proteins (genes) 1. recessive 2. 2 important clotting genes are sex-linked

  15. C. Sickle-cell disease (anemia) 1. caused by defective hemoglobin mutation of one allele causes a single amino acid change

  16. C. Sickle-cell disease (anemia) 2. those homozygous for the sickle-cell allele will have the disease

  17. C. Sickle-cell disease (anemia) 3. those heterozygous are basically normal pleiotropy: when a gene produces multiple effects advantage in resisting malaria

  18. D. Tay-Sachs 1. caused by a recessive allele 2. leads to deterioration of the nervous system (8 months) 3. increased incidence in certain populations certain Jewish populations in U.S. : 1 in 27 people of Jewish descent carriers 1 in 250 in general population

  19. Cystic fibrosis PKU

  20. Inbreeding increases the likelihood of recessive disorders.

  21. Dominant disorders: Huntington’s disease Achondroplasia

  22. Pedigrees:

  23. Amniocentesis: performed between weeks 14 and 20.

  24. CVS: performed as early as 8 weeks.

  25. Blood tests: 1. alpha-fetoprotein (AFP) high in neural tube defect low in Down syndrome 2. triple screen (now quad screen) - can even indicate trisomy 18 risk 3. these tests are not diagnostic, only reflective of risk

More Related