CHAPTER 12 HUMAN GENETICS

1. CHAPTER 12HUMAN GENETICS

2. Chromosomal Abnormalities • 1 infant in 200 newborns has a chromosomal abnormality • 28% of first trimester miscarriages have a chromosomal abnormality • Abnormalities in larger chromosomes don’t usually survive

3. Color Blindness Cause: Mutation in gene on X chromosome Symptoms: • More common in males (8% of males are colorblind) • Can’t distinguish certain colors • Most common = red/green Can you see the numbers and shapes?

4. Hemophilia Cause: change in gene on X chromosome that codes for blood clotting protein • Symptoms: • More common in males • Internal and external bleeding • Can result in death • Transfusions & hospitalization are required frequently to • stop bleeding!

5. Cystic Fibrosis • Mutation in gene on chromosome 7 • Symptoms: • More common in Caucasians • Make extra thick mucous in lungs and pancreas which leads to respiratory and digestive complications • Salty skin is clue

6. Achondroplasia(Dwarfism) Cause: (Autosomal DOMINANT- found on chromosome 4) Most new mutations in egg or sperm cell, but can be inherited from parent with gene • 1 in 20,000 births • 200,000 “little people” worldwide • Normal size torso; short arms and legs

7. Deletion Piece of DNA code is lost

8. Wolf-Hirschhorn syndrome • Deletion on arm of chromosome 4 • Mental retardation • Large low set ears • Club feet

9. Cri-du-chat “cry of the cat” • Deletion on arm of chromosome 5 • 1 in 50,000 births • More common in girls • Mewing cry in infancy • Mental retardation

10. Prader-Willi Syndrome • Deletion in chromosome 15 • Feeding problems: poor weight gain in infancy, won’t eat • Ages 1-6 excessive, rapid weight gain Victor at age 1 Victor at age 2

11. Duchenne Muscular Dystrophy Symptoms: • Deletion in gene on X chromosome • 1 in 3500 male births • Appears before age 5 • Progressive muscle weakening • Most in wheelchair by age 13 • Eventually lethal Jerry Lewis telethon

12. Non-disjunction A homologous pair sticks together and doesn’t separate at MEIOSIS. One cell gets 2 copies of the chromosome the other cell gets none. Monosomy- 1 chromosome Trisomy- 3 chromosomes

13. Down’s syndrome (trisomy 21) • Most common chromosomal abnormality • 1 in 660 births • Similar facial features • Slanted eyes • Protruding tongue • Mental retardation • Risk increases with age of mom

14. Patau syndrome (trisomy 13) • 1 in 7000 births (rare) • Cleft lip & palate • Eye abnormalities • (too small or missing) low set ears polydactyly

15. Kleinfelter syndrome XXy • 1 in 1000 births • Male = XXy • Average to slight decrease in intelligence • Small testes/can’t have children • Usually not discovered until puberty when don’t mature like peers • Has breast tissue & poor beard growth

16. Turner’s syndrome (X) • 1 in 5000 births • Female = X • Small size • Slightly decreased intelligence • Hearing loss common • Undeveloped ovaries/can’t have children

17. Xyy syndrome • Xyy males • Taller, more aggressive • Some early studies showed greater incidence of Xyy males in prison populations than in the normal population

18. Substitutions Can YOU find the difference? the fat cat ran and ran the fat rat ran and ran Sickle Cell Anemia is caused by this.

19. Sickle Cell Anemia • Substitution on chromosome #11 • A is changed to T

20. Insertion (addition) Extra Piece of DNA is added to code

21. Huntington’s • Insertion at end of gene on chromosome 4 • Degenerative brain disorder • Symptoms appear at age 30-40 (Usually after having children) • Lose ability to walk, think, talk, reason • 50/50 chance of passing it to child Now there is a test to tell if you have the gene before symptoms appear. Would you want to know?

22. How can we detect disorders?

23. What is wrong with this karyotype? Karyotype • Can tell missing/extra chromosomes • Gender • Some deletions/additions

24. Amniocentesis • Insert needle into sac and withdraw • fluid containing baby’s cells • Done at 14-16 weeks • Can detect: • Cystic Fibrosis • Huntington’s • missing/extra chromosomes

25. The End.