Ch. 7

Question 1

Multifactoral Traits

Answer 1

controlled by more than one gene, as well as environmental influences

Question 2

Polygenic Traits

Answer 2

controlled by more than one gene

Question 3

Epigenetic modification

Answer 3

heritable changes to DNA that regulate gene expression without altering the DNA sequence

Question 4

Heritability

Answer 4

estimates the proportion of variation in a complex trait due to genetics in a particular population at a certain time

degree of variation in a trait due to genetics (<1.0 = variability is completely the result of gene action)

Higher the number = higher genetics play a role, lower the number = outside factors

Question 5

Dizygotic Twins

Answer 5

shared environment and 50% of genes

Question 6

Monozygotic Twins

Answer 6

identical genotype and shared environment

Question 7

Twins Raised Apart

Answer 7

shared genotype but not environment

Question 8

Adopted Individuals

Answer 8

Shared environment but not genes

Question 9

Genome-Wide Association Studies (GWAS)

Answer 9

compares many genetic markers across the genome between two large groups of people (includes SNP’s and copy number variants (CNV’s) )

Question 10

Single Nucleotide Polymorphisms (SNP’s)

Answer 10

sites in a genome where the DNA base varies in at least 1% of the population, span the genome rather than define a single gene, can be anywhere among base pairs

GWAS must include at least 100k markers

Question 11

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

Answer 11

genes; Inherited disorders such as Down syndrome are influenced by genes.

Question 12

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

Answer 12

environment; When a fetus touches fingers and toes to the walls of the amniotic sac, the environment is influencing the phenotype.

Question 13

Height is affected by diet

Answer 13

environment

Question 14

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

Answer 14

genes; SNPs, or single nucleotide polymorphisms, are sites in the genome, so the influence of SNPs on human height is a genetic factor.

Question 15

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

Answer 15

genes & environment; An allele is a genetic influence. Smoking or not smoking, however, is an environmental factor. In this example, an allele of the E4 gene is interacting with the environment (smoking or non-smoking), so both genes and the environment are influencing the risk of heart disease in this example.

Question 16

Exercise decreases the risk of heart disease

Answer 16

environment

Question 17

Exposure to the sun increases melanin synthesis

Answer 17

environment

Question 18

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

Answer 18

False; If a trait is determined entirely by genes, then its heritability is 1.0.

Question 19

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

Answer 19

True

Question 20

The heritability of a single-gene trait is always 1.0

Answer 20

False; Single-gene traits may be influenced by the environment, so their heritability is not always 1.0.

Question 21

The heritability of a trait changes when the environment changes.

Answer 21

True

Question 22

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

Answer 22

False; If the heritability of a trait is high, then 50% of siblings will have the same phenotype because siblings share 50% of their alleles.

Question 23

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

Answer 23

False; Genetic variance is due mainly to the additive effects of recessive alleles of different genes, not dominant alleles.

Question 24

Identical twins are also called ___ twins.

Answer 24

monozygotic

Question 25

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.

Answer 25

concordance

Concordance is the percentage of twin pairs in which both twins express a trait among twin pairs in which at least one twin expresses the trait.

Question 26

Twins who differ in a trait are ___ for the trait.

Answer 26

discordant

Question 27

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

Answer 27

100%

Question 28

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

Answer 28

50%

Question 29

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

Answer 29

25%

Question 30

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

Answer 30

greater than

Question 31

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

Answer 31

monozygotic twins separated at birth

Question 32

Fertility in humans is a trait that is controlled by multiple genes, and which has environmental influences, such as the health and nutrition of the potential parents.

What terms describe fertility as a trait?

Answer 32

polygenic, complex, multifactoral

Monogenic or Mendelian traits are single-gene traits. Since fertility is controlled by multiple genes, these do not apply. Instead, fertility is a polygenic trait, because it is controlled by more than one gene. It is also a complex, or multifactorial trait, because it is influenced by an environmental factor.

Question 33

Which best describes use of polygenic risk scores in making illness/disease predictions in populations?

Answer 33

Single nucleotide base changes in multiple genes from a genome wide association (GWAS) study of an illness/disease risk of one population are used to make predictions of illness using algorithms in another group.