Mutations and other genetic issues

1. Mutations and other genetic issues Genetics Unit

2. Mutations • Changes in the genetic material. • Any deviation from the normal chromosomal compliment • Two types: • Spontaneous mutations-occur randomly; no cause can be determined • Induced mutations are caused by some traceable artificial factor: exposure to chemicals, alcohol, drugs, radiation

3. Mutations • Mutations that produce changes in a single gene are gene mutations. • Mutations that produce changes in a whole chromosome are chromosomal mutations.

4. Gene Mutations • Point mutation-change in one or just a few nucleotides. So named because it occurs at a single point. • Substitutions • Deletions • Insertions

5. Gene Mutations • Frameshift mutation—shift the reading frame of the genetic code • Can alter a protein so much that it can’t perform its job.

6. Chromosomal Mutations • Involve a change in the number or structure of the chromosome • Some change the location of some genes on the chromosome • Some may change the number of copies of some genes.

7. Chromosomal Mutations • Four main types of mutations: • Deletion • Duplication • Inversion • translocation

8. Deletion • The permanent loss of a segment of chromosome • Can be found anywhere on the chromosome • Can be caused by heat, radiation, viruses, chemicals, errors

9. Deletion

10. Duplication • Doubles a segment of chromosome • Can be fatal • Can be caused by uneven crossing over during meiosis or replication error before meiosis

11. Duplication

12. Causes of abnormalities • Nondisjunction • The failure of the chromosome pairs to separate during Meiosis I or Meiosis II • Result will be a zygote with too many or too few chromosomes • Two types: Primary and secondary nondisjunction

13. Primary Nondisjunction

14. Secondary Nondisjunction

15. Types of Genetics Tests • When trying to determine a genetic problem, we can use non-invasive tests such as • Pedigrees • Karyotypes

16. Pedigrees • A pedigree follows a specific trait through several generations • Resembling a type of map, the pedigree uses symbols to represent certain elements

17. Pedigree key

18. Pedigree

19. Karyotypes • A photographic inventory of an individual’s chromosomes • Can show the individual’s gender and any abnormalities in chromosome number or structure

20. Karyotypes

21. Karyotypes

22. Amniocentesis • An invasive test that obtains amniotic fluid surrounding the fetus using a needle

23. Amniocentesis Pros and Cons • Able to determine fetus’ gender and/or any abnormalities • Can’t be done before 16th week of pregnancy • Can cause infection to mother and/or fetus • Can cause premature delivery and birth

24. Chorionic Villus Sampling (CVS)

25. CVS Pros and Cons • Can determine fetus gender and any genetic abnormalities • Can be done after 10 weeks • Can cause leakage of amniotic fluid • Can cause premature labor and delivery

26. Recessive Disorders • Must be inherited from BOTH parents • Autosomal recessive disorders (non-sex cells) • Tay-Sachs • PKU • Cystic fibrosis

27. Recessive Disorders • Tay-Sachs—lipid accumulation in the brain; mental deficiency; blindness, death in early childhood • PKU-phenylketonuria—accumulation of phenylalanine in tissues; lack of normal skin pigment; mental retardation • Cystic fibrosis—excess mucus in lungs, digestive tract, liver; increased susceptibility to infections; often die young

28. Dominant Disorders • Can get the disorder by inheriting only one dominant allele • Huntington’s disease • Achondroplasia

29. Dominant Disorders • Huntington’s Disease • Mental deterioration and uncontrollable movements • Doesn’t appear until middle age • Achondroplasia • One form of dwarfism

30. Sex Linked Disorders • Is there a pattern of inheritance for genes located on the X or Y chromosome? YES especially on the X • Many times it is male children that inherit these disorders from their mothers because . . . They inherit their X from their mom’s Many sex linked genes are on the X • Colorblindness • Hemophilia • Duchenne Muscular Dystrophy

31. Sex Linked Disorders • Colorblindness • Most often found in males • 1 in 10 males • Females have to inherit from both parents • 1 in 100 females • Most common is red-green colorblindness

32. Sex Linked Disorders • Hemophilia • Two genes on the X chromosome control blood clotting • Many times it is male children that inherit this from their mom’s X chromosome • 1 in 10,000 males • A bleeding disorder; can cause death in severe cases

33. Sex Linked Disorders • Duchenne Muscular Dystrophy • 1 in 3000 males • Progressive weakening and loss of skeletal muscle • Caused by defective version of gene that codes for a muscle protein

34. Genetic Disorders • Trisomy • Downs Syndrome (extra chromosome 21) • Patau Syndrome (extra chromosome 13) • Edwards Syndrome (extra chromosome 18)

35. Downs Syndrome (Trisomy 21)

36. Edwards Syndrome (Trisomy 18)

37. Patau Syndrome (Trisomy 13)

38. Turner’s Syndrome

39. Turner’s Karyotype

40. Klinefelter’s Syndrome