Chromosomes & Karyotypes

1. Chromosomes & Karyotypes

2. Chromosomes

3. Chromosome Number • All cells in the human body (SOMATIC CELLS) have 46 or 23 pairs of chromosomes • Called the DIPLOID or 2n number • GAMETES (eggs & sperm) have only 23 chromosomes • Called the MONOPLOID or 1n number

4. Nondisjunction • Chromosomes may fail to separate during meiosis • Resulting gametes may have too few or too many chromosomes • Examples of chromosomal disorders: • DownSyndrome – three #21 chromosomes • Turner Syndrome – single X chromosome • Klinefelter’s Syndrome – XXY chromosomes

5. Karyotype • A picture of a person’s chromosomes

6. Normal Male 2n = 46

7. Normal Female 2n = 46

8. Male, Trisomy 21 (Down’s) 2n = 47

9. Female Down’s Syndrome 2n = 47

10. Downs Syndrome • Set of symptoms that can range from mild to severe • Slower mental and physical development • Flat face with an upward slant to the eye, short neck, and abnormally shaped ears • Poor muscle tone, loose ligaments • Heart disease • Eye problems • Intestinal problems

12. Klinefelter’s Syndrome 2n = 47

13. Klinefelter’s syndrome • Male • Don’t produce enough testosterone • Smaller testes • Breast enlargement • Reduced body and facial hair • Most infertile • Increased risk of breast cancer • May have learning disabilities • 1 in 500 births

15. Turner’s Syndrome 2n = 45

16. Turner Syndrome • Short stature • Ovaries don’t function correctly • Won’t go through puberty unless treated with hormones • 1/3 have extra folds on the neck • 1/3 have heart defects • 1 in 2500 births (many miscarry, though)

18. Pedigree Charts The family tree of genetics

19. What is a Pedigree? A pedigree is a chart of the genetic history of family over several generations. Scientists or a genetic counselor would find out about your family history and make this chart to analyze.

20. Constructing a Pedigree Male Female

21. Connecting Pedigree Symbols Married Couple Siblings Examples of connected symbols:

22. Example What does a pedigree chart look like?

23. Interpreting a Pedigree Chart Determine if the pedigree chart shows an autosomal or X-linked disease. If most of the males in the pedigree are affected the disorder is X-linked If it is a 50/50 ratio between men and women the disorder is autosomal.

24. Example of Pedigree Charts Is it Autosomal or X-linked?

25. Answer Autosomal

26. Interpreting a Pedigree Chart Determine whether the disorder is dominant or recessive. If the disorder is dominant, one of the parents must have the disorder. If the disorder is recessive, neither parent has to have the disorder because they can be heterozygous.

27. Example of Pedigree Charts Dominant or Recessive?

28. Answer Dominant

29. Example of Pedigree Charts Dominant or Recessive?

30. Answer Recessive

31. Examples of recessive traits Albinism – lack of hair and skin pigmentation Tay-Sachs – fatal disease that causes nerve damage Cystic fibrosis – defective protein needed for lungs and digestion

35. Examples of dominant traits Achodroplasia – dwarfism – 1 out of 25,000 Huntington’s disease – degeneration of nervous system leading to death