Reference no: EM133920844

Question 

Chapter 5

Responding to an advertisement in a college newsletter, one set of adopted twins (one male twin and one female twin) arrives at a research center in a local hospital. The study involves a generalized health assessment, some basic medical tests, and a psychologic examination. Participants will learn of any predispositions they may have toward a variety of disease processes. The twins have brought a vague family history from their natural parents and their adoptive parents. Twin studies and adoption studies are often used to estimate the relative influence of genes and environmental factors. This particular set of twins is dizygotic, which means they are the result of double ovulation, followed by the fertilization of each egg by a different sperm. Monozygotic twins are an example of natural clones; that is, the developing embryo divides to form two separate but identical embryos. Dizygotic twins are an important because although they may share environmental influences, their genetics are as great as those among siblings.

The female twin has a history of a cleft palate, whereas the male twin does not. This trait would be considered to be:

1. Discordant
2. Concordant
3. Multifactorial
4. Quantitative

Multifactorial inheritance is influenced by which factor?

1. The recurrence risk is higher if the proband is of the less commonly affected sex.
2. The expression of the disease in the mother dictates the recurrence risk.
3. Those with a lower threshold have a lower incidence rate.
4. The highest risk generally falls to male relatives of a female proband.