1. Chapter 13 Genetic Disorders
Advanced Biology
Chapter 13
Genetic Disorders

2. Autosomes – 22 perfectly matched chromosomes.

3. Sex Chromosomes – 23rd pair
XX = Female
XY = Male

5. Monosomic – Lost one copy of a chromosome
Usually fatal, especially if on an autosome

6. Trisomic – Extra chromosome
13, 15, 18 can have an extra and survive for a short time
21, 22 can survive into adulthood

7. Down Syndrome – Trisomy 21
Extra copy of the 21st chromosome

9. Primary Nondisjunction – Failure of chromosomes to separate during Meiosis

10. Failure to separate is correlated to age:
>20 – 1:1700 births
20-30 – 1:1400
30-35 – 1:750
35-45 – 1:16

11. Barr Body – One of the X chromosomes is inactivated

14. Y Chromsome – Possesses some active genes, contains features associated with male-ness
Contains 78 genes

16. NONDISJUNCTION IN SEX CHROMOMSOMES
Triple X syndrome - XXX
One functional X, two Barr Bodies
Female is sterile but normal in other respects
NONDISJUNCTION IN SEX CHROMOMSOMES

17. NONDISJUNCTION IN SEX CHROMOMSOMES
Klinefelter Syndrome – XXY
Sterile Male
Has many female characteristics
May have diminished mental capacity
1:500
NONDISJUNCTION IN SEX CHROMOMSOMES

18. NONDISJUNCTION IN SEX CHROMOMSOMES
Turner Syndrome – XO
Sterile Female
Short in stature, webbed neck
Sex organs never fully mature
Low mental abilities
1:5,000
NONDISJUNCTION IN SEX CHROMOMSOMES

19. NONDISJUNCTION IN SEX CHROMOMSOMES
Nonviable – OY
Fails to develop
Humans cannot survive without the genes on the X chromosome
NONDISJUNCTION IN SEX CHROMOMSOMES

20. Multiple alleles – Some traits possess multiple alleles for that specific trait
Blood types.

21. GENETIC DISORDERS Cystic Fibrosis Autosomal
Occurs mainly in the white population
1:20 carry the allele
1:1800 are homozygous recessive
GENETIC DISORDERS

22. A malfunction in a channel protein causes a thick mucus to be produced in the lungs
Can also affect ducts in the pancreas
Most affected individuals die in their teens
GENETIC DISORDERS

23. GENETIC DISORDERS Sickle Cell Anemia Autosomal Recessive
Occurs more frequently in the black pop.
1:1600
GENETIC DISORDERS

24. Hemoglobin is defective; doesn’t carry enough Oxygen
GENETIC DISORDERS

26. Phenylketonuria (PKU)
Autosomal recessive
1:15,000
GENETIC DISORDERS

27. GENETIC DISORDERS Inability to breakdown phenylalanine (aa)
Can be controlled by nutrition
GENETIC DISORDERS

29. GENETIC DISORDERS Tay-Sachs Disease Autosomal Recessive
1:3600 if of Jewish decent
1:300,000 in U.S
GENETIC DISORDERS

30. Affected individuals lack an enzyme that breaks down gangliosides in the brain
These accumulate in the lysosome and burst
Resulting in the destruction of brain cells
GENETIC DISORDERS

31. GENETIC DISORDERS Sex-linked recessive Inability of blood to clot
Missing a clotting factor
GENETIC DISORDERS

33. GENETIC DISORDERS Huntington’s Disease DOMINANT 1:10,000
Gene gets turned on in middle age
GENETIC DISORDERS

34. Deterioration of brain cells due to the inhibition of brain cell metabolism
GENETIC DISORDERS

35. GENETIC DISORDERS High risk pregnancies Parents who are:
Heterozygous for a disease
Older
OR have a family history
GENETIC DISORDERS

36. GENETIC COUNSELING Ultrasound – position of fetus Amniocentesis
Withdraw fluid containing fetal cells
GENETIC COUNSELING

38. GENETIC COUNSELING Chorionic Villi Sampling
Take a sample of placental tissue
GENETIC COUNSELING

40. GENE THERAPY Gene Transfer Therapy 1st done in 1990
2 Girls had a rare blood disorder due to a defective gene
Scientists isolated working copies of the gene
GENE THERAPY

41. Introduced them into bone marrow cells taken from each girl
Gene modified bone marrow cells were allowed to proliferate (make more)
Injected back into body
Both girls healthy
GENE THERAPY

42. GENE THERAPY Use of vectors (1995)
Attach gene to a virus – adenovirus (cold)
Like a piggyback ride
Tried it with mice and the cf gene
GENE THERAPY

43. GENE THERAPY Worked, tried it with humans
Worked for awhile, but eventually immune system attacked virus
Caused the loss of the good gene
GENE THERAPY

44. GENE THERAPY Problems with the vector:
Adenovirus elicits a strong immune response (everyone has had a cold)
Adenovirus can produced a severe immune reaction and be fatal
GENE THERAPY

45. GENE THERAPY Problems with the vector:
Adenovirus inserts its DNA into cell at a random location causing mutations
GENE THERAPY

46. GENE THERAPY Few years later, found new vector
Use Parovirus called Adeno-Associated Virus (AAV)
Has only two genes and needs the adenovirus to replicate
GENE THERAPY

47. Scientists removed the two genes and insert human genes in their place to take them into the cell
Does not cause the problems that the adenovirus did
GENE THERAPY

48. GENE THERAPY In 1999, AAV cured anemia in rhesus monkeys.
Also cured dogs of retinal degeneration
In 2000 first human trial
GENE THERAPY