Chapter 20, Problem 2RQ

Identify a possible advantage and a possible disadvantage of a genetic test that would identify genes in individuals that increase their probability of having Alzheimer’s disease later in life.

A pedigree analysis was performed on the family of a man with schizophrenia. Based on the known concordance statistics, would his MZ twin be at high risk for the disease? Would the twins risk decrease if he were raised in an environment different from that of his schizophrenic brother?

Why are monozygotic twins who are reared apart so useful in the calculation of heritability?

Why are relatives used in the calculation of heritability?

Why do unrelated children with a disorder such as Down syndrome resemble each other more closely than they do their siblings?

How is heritability related to genetic and environmental variance?

Still referring to Problem 1, what will be the possible genotypes of offspring from the following matings? With what frequency will each genotype show up? a. AABB aaBB b. AaBB AABb c. AaBb aabb d. AaBb AaBb

Individuals of genotype AaBb were mated to individuals of genotype aabb. One thousand offspring were counted, with the following results: 474 Aabb, 480 aaBb, 20 AaBb, and 26 aabb. What type of cross is it? Are these loci linked? What are the two parental classes and the two recombinant classes of offspring? What is the percentage of recombination between these two loci? How many map units apart are they?

What is the genetic basis and phenotype for each of the following disorders (use proper genetic notation)? a. Edwards syndrome b. Patau syndrome c. Klinefelter syndrome d. Down syndrome