chapter 7

Diseases caused by single genes that approach 100 percent penetrance approach _______ concordance in monozygotic twins.

100 percent

Among dizygotic twins, concordance is usually around ______ for a recessive trait.

25

Among dizygotic twins, concordance is usually around ____ for a dominant trait.

50

A trait that is influenced by only one gene is a __________ trait.

Mendelian

If there is a(n) _________ between two events, then one occurs when the other occurs.

association

Scientific studies of body weight use a measurement called ________ , which is weight in proportion to height

body mass index

A certain allele of the E4 gene, which encodes apolipoprotein E, increases the risk of a heart attack in people who smoke but not in people who do not smoke

both

In a(n) _____________, each individual in one group is matched to an individual in another group who shares as many characteristics as possible.

case-control study

The proportion of genes that two people with a certain relationship share is the ____________

coefficient of relatedness.

In a(n) _________, researchers follow a large group of individuals over time.

cohort study

Among pairs of twins in whom at least one has a particular trait, the _______ of the trait is equal to the percentage of pairs in which both twins express the trait.

concordance

Among pairs of twins in whom at least one has a trait, the percentage of pairs in which both twins express the trait is the ________ of the trait.

concordance

If there is a(n) ________ between two characteristics, then if one measurement increases, the other characteristic changes in a predictable direction.

correlation

wins who differ in a trait are ________ for the trait.

discordant

The chance that a polygenic multifactorial trait will occur in an individual is the _________

empiric risk.

Fingerprint patterns are altered when a fetus touches fingers and toes to the walls of the amniotic sac.

enviorment

Height is affected by diet.

enviorment

Exposure to the sun increases melanin synthesis.

enviornment

Exercise decreases the risk of heart disease

environment

All genes that influence a polygenic trait contribute equally to the phenotype

false

Calculations of empiric risk are based on Mendel's laws.

false

Genetic variance for a polygenic trait is due mainly to the additive effects of dominant alleles of different genes

false

If a trait is determined entirely by genes, not by the environment, then the heritability of the trait is 0

false

If the heritability of a trait is very high, then all siblings will have the same phenotype.

false

Polygenic traits have all-or-none phenotypes.

false

Prevalence is the number of new cases of a disorder that are diagnosed per year in a population of a given size.

false

The heritability of a single-gene trait is always 1.0

false

The individual genes that contribute to a polygenic trait are dominant or recessive to each other.

false

To use empiric risk to predict the likelihood that an individual will have a disorder, it is necessary to understand the transmission pattern of the disorder.

false

When a trait is polygenic, individuals cannot be categorized into classes with respect to their phenotypes

false

Certain patterns of SNPs are common in individuals who experience a period of rapid height increase.

genes

Some inherited disorders (such as Down syndrome) are associated with unusual fingerprint ridge patterns

genes

A(n) ______ seeks correlations between SNP patterns and phenotypes in large groups of individuals.

genome-wide association study

The hormone that is produced by the stomach in response to hunger is

ghrelin

For a polygenic trait with little or no environmental influence, the concordance value for monozygotic twins will be _________ the concordance value for dizygotic twins.

greater than

The proportion of phenotypic variance for a trait that is due to genetic differences in a population is the trait's ____________

heritability.

In _________ families that are consanguineous are studied.

homozygosity mapping

The number of new cases of a genetic disorder diagnosed per year in a population of a given size is the ___________ of the disorder.

incidence

The protein hormone ________ stimulates the hypothalamus to decrease appetite.

leptin

Identical twins are also called _________ twins.

monozygotic

To assess the genetic component of a multifactorial trait, it would be most appropriate to study ___________

monozygotic twins separated at birth

A trait that is influenced by both genes and the environment is a __________ trait.

multifactorial

A trait that is influenced by two or more genes is a _________ trait

polygenic

The __________ of a genetic disorder is the proportion of individuals in a population who have the disorder at a specific time.

prevalence

DNA sequences that contribute to polygenic traits are called ___________

quantitative trait loci

Treatment with leptin results in weight loss for some people but not for others. Leptin resistance, or unresponsiveness to leptin when it is given as a drug, is due to mutations in the gene that encodes _________

the leptin receptor

DNA sequences that contribute to polygenic traits are called quantitative trait loci.

true

Empiric risk increases with the number of family members who are affected with the disorder.

true

Empiric risk increases with the severity of the disorder.

true

Heritability is defined as the proportion of the phenotypic variance for a trait that is due to genetic differences in a population at a certain time

true

Polygenic traits may be influenced by the environment.

true

The graph of the frequency of phenotypes in a polygenic trait has the shape of a bell curve.

true

The heritability of a trait changes when the environment changes.

true