Exam 18: The Genetic and Environmental Basis of Complex Traits

Consider a trait determined entirely by environmental risk factors for which the chance that a random individual is affected is 20%. What is the concordance between identical twins? What is the concordance between same-sex fraternal twins?

Using identical twins to study heritability is complicated by the fact that:

Lack of exercise is an example of a(n) _____ for/of obesity and diabetes.

Current evidence BEST supports which statement about the relative number of genes and their effects in most complex traits?

In twin studies, scientists measure concordance, which is defined as the:

When identical twins differ in phenotype of a complex trait, it is almost always due to:

Environmental effects have no impact on true-breeding, homozygous strains (inbred lines) of plants or animals.

One hope of personalized medicine is that:

In regard to gaining weight, some human genotypes may tolerate a high-fat diet more than others.

Consider a trait determined by a rare mutation in the Y chromosome. What is the concordance between male twins? Between fraternal twins that are both male?

If all variation among individuals in a population is due to differing genotypes alone, heritability is _____, and the slope of the line used to measure it is _____.

The data in the graph below show the concordance between identical twins and same-sex fraternal twins for five complex traits. Based on these data, which of the traits shows the GREATEST effect of heredity relative to environment?

In general, the phenotypes of a complex trait should exhibit a(n) _____ distribution.

A new mutation arises that affects a complex trait. In most cases, its effect is likely to be:

When considering complex traits in health and disease, which of the following statements is NOT correct?

Inbred lines of animals, such as laboratory mice, are useful for studying complex traits because:

Although more than 50 genes contribute to the level of HDL (high-density lipoproteins), LDL (low-density lipoproteins), or triglycerides, it has also been shown that a single gene within this population of genes can affect two or three of these types of molecules. This single gene with its multiple effects is said to show:

In a parent-offspring regression experiment, suggest a hypothesis that could explain the solid line in the following graph.

One day, scientists will be able to cure obesity by targeting a single gene.

Which of the traits depicted here has the GREATEST heritability?