Question 1

Which genes are responsible for an autosomal dominant form of breast cancer?

Accepted Answer

Women who inherit a mutation in BRCA1 or BRCA2 experience a 50% to 80% lifetime risk of developing breast cancer.

Question 2

The data reporting that sickle cell disease affects approximately 1 in 600 American blacks is an example of which concept?

Accepted Answer

Prevalence rate is the proportion of the population affected by a disease at a specific point in time. Prevalence is thus determined by both the incidence rate and the length of the survival period in affected individuals.

Question 3

Which risk factor for hypertension is influenced by genetic factors and lifestyle?

Accepted Answer

The most important environmental risk factors for hypertension are increased sodium intake, decreased physical activity, psychosocial stress, and obesity (but, as discussed later, the latter factor is itself influenced by genes and environment).

Question 4

If a woman has one first-degree relative with breast cancer, her risk of developing breast cancer is _____ times what it would otherwise be.

Accepted Answer

If a woman has one affected first-degree relative, her risk of developing breast cancer doubles.

Question 5

Environmental modification can reduce risk for developing diseases that have a genetic and environmental component.

Accepted Answer

Most of the diseases discussed in this chapter have genetic and environmental components. Thus, lifestyle modification (e.g., diet, exercise, stress reduction) often can reduce risk significantly.

Question 6

An autosomal dominant form of breast cancer accounts for ____% of all cases.

Accepted Answer

An autosomal dominant form of breast cancer accounts for approximately 5% of breast cancer cases in the United States.

Question 7

The _____ risk of developing a disease is expressed as the ratio of the disease rate among the exposed population to the disease rate in an unexposed population.

Accepted Answer

A common measure of the effect of a specific risk factor is the relative risk.

Question 8

When the offspring of a parent with schizophrenia are adopted by parents without schizophrenia, their risk of developing the disease is about 25%, which is about half the risk when they are raised by their biologic parents.

Accepted Answer

When the offspring of a schizophrenic parent are adopted by normal parents, their risk of developing the disease is about 10%, which is approximately the same as the risk when raised by a schizophrenic biologic parent.

Question 9

Relative risks indicate the percentage of disease cases in the general population that are attributable to a specific risk factor.

Accepted Answer

A common measure of the effect of a specific risk factor is the relative risk.

Question 10

Some families are more susceptible to colorectal cancer than other families.

Accepted Answer

Like breast cancer, it clusters in families (in fact, familial clustering of this form of cancer was reported in the medical literature as early as 1881).

Question 11

Cancers that cluster strongly in families include:

Accepted Answer

Lung and colon cancers have proven to show a strong familial tendency.

Question 12

The prevalence rate is the number of new cases of a disease reported during a specific time period.

Accepted Answer

The incidence rate can be contrasted with the prevalence rate, which is the proportion of the population affected by a disease at a specific point in time. Prevalence is thus determined by both the incidence rate and the length of the survival period in affected individuals. The incidence rate is the number of new cases of a disease reported during a specific period (typically 1 year) divided by the number of individuals in the population.

Question 13

Empirical risks for most multifactorial diseases are based on:

Accepted Answer

For most multifactorial diseases, empirical risks (i.e., risks based on direct observation of data) have been derived.

Question 14

A low-fat and high-fiber diet is thought to increase the risk of colon cancer.

Accepted Answer

Environmental factors, such as a high-fat, low-fiber diet, are thought to increase the risk of colorectal cancer.

Question 15

Breast cancer manifests in familial patterns.

Accepted Answer

Breast cancer aggregates strongly in families.

Question 16

Alzheimer disease is thought to have a genetic predisposition.

Accepted Answer

The risk of developing Alzheimer disease doubles in individuals who have an affected first-degree relative.

Question 17

The blending of multiple genes and environmental influences results in the production of a multifactorial trait.

Accepted Answer

Traits in which variation is thought to be caused by the combined effects of multiple genes are polygenic ("many genes"). When environmental factors are also believed to cause variation in the trait, which is usually the case, the term multifactorial trait is used.

Question 18

The recurrence risk becomes higher if more than one family member has a multifactorial disease.

Accepted Answer

The recurrence risk becomes higher if more than one family member is affected.

Question 19

What is the cause of familial hypercholesterolemia (FH)?

Accepted Answer

FH is caused by a reduction in the number of functional LDL receptors on cell surfaces. Lacking the normal number of LDL receptors, cellular cholesterol uptake is reduced and circulating cholesterol levels increase (Box 5-3).

Question 20

The body weight of adopted children correlates significantly with the body weights of their adopted parents.

Accepted Answer

Four adoption studies each showed that the body weights of adopted individuals co-related significantly with their natural parents' body weights but not with those of their adoptive parents.

Quiz 5: Genes, Environment, and Common Diseases