Chapter 22 Medical Genetics and Cancer

What is the inheritance pattern when a trait occurs with the same frequency in both sexes and an affected offspring can have two unaffected parents?

Autosomal recessive

The accompanying pedigree shows the inheritance of Huntington disease with filled symbols and also indicates which combination of four possible forms (A, B C, D) of a molecular marker called G8 that the person has inherited. Consider the couple that is surrounded by the red circle. Of their possible children, what phenotype and marker combination is missing?

BB without Huntington disease

The accompanying pedigree shows the inheritance of Huntington disease with filled symbols and also indicates which combination of four possible forms (A, B C, D) of a molecular marker called G8 that the person has inherited. Although there are some exceptions, the inheritance of Huntington disease is most closely associated with which form of the G8 marker in this pedigree?

C

For the inherited tendency to develop retinoblastoma in the first few years of life, which correctly describes inactivation of the rb tumor-suppressor alleles by the "two-hit" model?

One allele is inactivated prior to birth, the other becomes inactivated early in life.

For the non-inherited development of retinoblastoma, which correctly describes inactivation of the rb tumor-suppressor alleles by the "two-hit" model?

The person is born with two active copies of the rb allele; separate mutation events are required to inactivate each of these alleles.

Clinical improvement in leukemia patients has been observed when providing drugs that inhibit the enzyme

DNA methyltransferase.

A method that can identify genes that are active in cancer cells but inactive in normal cells is

DNA microarray analysis.

Which methods can be used at the DNA level to test for specific mutations related to a genetic disease?

Fluorescence in situ hybridization (FISH) DNA microarray analysis DNA sequencing

The loss of a chromosome carrying a tumor-suppressor gene is an example of a way of losing the function of this gene through

aneuploidy

If alleles and molecular markers are associated with each other at a frequency greater than expected by random chance, the situation is described as

linkage disequilibrium.

The disease hemophilia is caused by a deficiency in any one of three blood clotting factors. Two of these factors are encoded by genes on the X chromosome and the other clotting factor gene is located on an autosome. Since mutations in more than one gene can cause hemophilia, this represents

locus heterogeneity.

To potentially reverse the inactivation of tumor-suppressor genes, researchers are developing potential cancer treatments that involve inhibition of the enzyme DNA

methyltransferase

If an increase in DNA methylation of a gene is associated with an increase in severity of a specific disease, these two variables show a(n)

positive correlation.