Alzheimer’s Disease

1. Alzheimer’s Disease Diego, Jackie, and Pete 1/27/10 Period 2

2. Summary of Genetic Disorder • Alzheimer’s Disease is a progressive and fatal brain disease. • Over 5 million people have it. • Early symptoms include memory loss, trouble concentrating, and inability to remember facts, events and later family and friends. • Alzheimer’s disease is the 4th leading cause of death in adults. • AD is twice as common in women than it is in men.

3. Affected Chromosomes • Alzheimer’s affects the 1st, 14th, 19th, and 21st chromosomes.

4. Mode of Inheritance • Alzheimer’s does have a genetic link, and it is a Dominant disorder. • FAD (Familial Alzheimer's Disease) occurs in a very small percentage of people with Alzheimer's disease (5-7%) • Sporadic Alzheimer's Disease is much more common (around 90-95 %) and people with this type do not necessarily have a family history of the disease.

5. Alleles • An allele is an alternative form of a gene (one member of a pair) that is located at a specific position on a specific chromosome. • Humans have 2 alleles per gene. • The two alleles come from both parents. • Recessive alleles are represented by rr. Dominant alleles are represented by RR or Rr. • Phenotypes are specified by single gene substitutions are called Dominants and those that require homozygous combinations for expression are called recessives.

6. Probability per child In the First Punnett square, the offspring has 75% chance of having Alzheimer's. In the second one, the probability is 100% and in the 3rd one its 50%. The last one has 100% also. Father w w G g 1 Father 2 W G Mother Mother W g Father Xr Y 4 h h 3 Father H XR Mother Mother XR h

7. Probability using ratios and percents Ratio: This Punnett square has 1GG : 2Gg : 1gg. Percentage: 25% GG, 50% Gg, and 25% gg . G g G g

8. Phenotypes and Genotypes G g The four squares in the middle are the chances for the offspring. GG is a Homozygous Dominant, Gg is a Heterozygous Dominate, and gg is a Heterozygous Recessive. G g The letters are the Genotypes, or what is in the genes. The Phenotypes are what you see. GG would mean that the offspring does have Alzheimer’s. Gg would also mean that, but gg would not since they are both recessive.

9. Genotypes and Phenotypes with Percentages and Ratios G g Phenotypes: Ratios: 3 with Alzheimer's disease, 1 without it. 3:1 Percentages: 75% will have it, 25% will not. G g Genotypes: Ratios: 1GG : 2Gg : 1gg. Percentages: 25% GG, 50% Gg, 25% gg.

10. Student Practice G G Fill in the offspring possibilities of them having Alzheimer’s Disease. After that is completed fill out the following: Genotype: Ratio: Percentage: Phenotype: Ratio: Percentage: G g 2GG : 2Gg 50% GG, 50% Gg 4 Alzheimer’s : 0 No Alzheimer's 100% Chance of Getting Alzheimer’s Disease.

11. 3 Generation Pedigree Chart Autosomal Dominant

12. Student Practice Red Square = affected male, Blue Square = not affected male. Red Circle = affected female, Blue circle = not affected female.

13. Questions 1. Are dominant conditions expressed in individuals who have just one copy of the mutant allele? 2. Do affected individual's have one normal copy of the gene and one mutant copy of the gene? 3. Will the offspring have a 75% chance of inheriting the mutated allele? Yes Yes No, a 50% chance.