Human Genetics Exam 2

In familial hypercholesterolemia, individuals homozygous for the allele causing the disorder completely lack receptors on liver cells that take up cholesterol from the blood stream. Heterozygotes have one-half the number of receptors while individuals homozygous for the normal allele are phenotypically normal. This is an example of _____.

A) complete dominance

B) codominance

C) incomplete dominance

D) epistasis

C) incomplete dominance

The gene A exhibits incomplete dominance. What can we expect about the offspring from the mating of two heterozygotes?

A) a 3:1 phenotypic ratio

B) phenotypic ratios that match the genotypic ratios

C) a 2:1 phenotypic ratio

D) an equal number of homozygous dominant phenotypes as intermediate phenotypes

B) phenotypic ratios that match the genotypic ratios

In humans, the dominance relationship between the A and B alleles of the ABO blood group gene is an example of _____.

A) complete dominance

B) incomplete dominance

C) codominance

D) epistasis

C) codominance

The relationship of the I and H genes affects the expression of the ABO blood type in the following ways: genotype HH or Hh, AB produces blood type AB while genotype hh, AB produces blood type O. This is an example of _____.

A) complete dominance

B) codominance

C) incomplete dominance

D) epistasis

D) epistasis

An environmentally caused trait that appears to be inherited is called a(n) _____.

A) pleiotropic gene

B) penetrant gene

C) expressed gene

D) phenocopy

D) phenocopy

The term _____ refers to the condition in which DNA bases in the mitochondrial genome differ within an individual.

A) Heteroplasmy

B) pistasis

C) Genetic Heterogeneity

D) Pleiotropy

A) Heteroplasmy

Two Mexican hairless dogs are crossed. What ratio of hairy: hairless dogs is expected in the offspring generation?

A) 3 hairless: 1 hairy

B) 3 hairy: 1 hairless

C) 2 hairless: 1 hairy

D) cannot be predicted

C) 2 hairless: 1 hairy

A woman with type A blood has a child with type A blood. Which of the following men could not be the father of this child?

A) A

B) B

C) AB

D) all could be the father

D) all could be the father

Alleles that are both expressed in a heterozygote are _____.

A) completely dominant

B) codominant

C) incompletely dominant

D) epistatic

C) incompletely dominant

The Bombay phenotype is a result of ____ interacting genes and is an example of ____.

A) 2; complete dominance

B) 2; incomplete dominance

C) 3; incomplete dominance

D) 2; epistasis

D) 2; epistasis

Some people with polydactyly do not have any extra digits; some have an extra toe, while others have an extra finger. This situation is an example of a trait that is:

A) incompletely penetrant.

B) variably expressive.

C) both a and b

D) neither a nor b

C) both a and b

Marfan Syndrome, a dominant single-gene defect, is characterized by lens dislocation, long limbs, spindly fingers, a caved-in chest, and a weakened aorta. This is an example of a(n) ____ trait.

A) multifactorial

B) pleiotropic

C) incompletely dominant

D) phenocopy

B) pleiotropic

When a teratogen causes a birth defect that is similar to a genetic disorder, this is referred to as _____.

A) genetic heterogeneity

B) pleiotropy

C) a phenocopy

D) epistasis

C) a phenocopy

A geneticist crosses a plant with red flowers to a plant with white flowers. The offspring include plants with red flowers (1/4), pink flowers (1/2), and white flowers (1/4). Which allele is dominant?

A) red

B) white

C) neither, they are incompletely dominant

D) neither, they are codominant

C) neither, they are incompletely dominant

Which of the following blood types is not possible from two parents with type A blood?

A) A

B) O

C) B

D) All of the above are possible.

C) B

The term that is used to describe the severity or extent of a phenotype in an individual is called _____.

A) pleiotropy

B) penetrance

C) expressivity

D) epistasis

C) expressivity

Which of the following diseases is an example of a pleiotropic condition?

A) cystic fibrosis

B) porphyria variegata

C) Leber congenital amaurosis

D) familial hypercholesterolemia

B) porphyria variegata

All of the following are features of mitochondrial DNA EXCEPT:

A) mutates faster than DNA in the nucleus.

B) maternal inheritance.

C) no crossing over.

D) one copy per mitochondrion.

D) one copy per mitochondrion.

If you examine a pedigree showing the transmission pattern of a mitochondrial gene mutation, which of the following statements would be false?

A) Mothers pass the gene to all offspring.

B) Fathers do not transmit the gene.

C) Only females will express the trait.

D) All of the above statements are true.

C) Only females will express the trait.

Only ____ transmit mitochondrial genes. Many mitochondrial disorders are ____, with mitochondria in a cell harboring different alleles.

A) males; heteroplasmic

B) males; heteromorphic

C) females; heteromorphic

D) females; heteroplasmic

D) females; heteroplasmic

Diseases resulting from mutations in mitochondrial genes affect _____.

A) mitochondrial protein synthesis

B) cellular energy reactions

C) both a and b

D) neither a nor b

C) both a and b

You are studying a degenerative condition that appears to be passed on only from the mother of the family. Affected fathers do not pass the trait to the offspring. This suggests that the trait might be _____.

A) mitochondrial

B) lethal

C) epistatic

D) incompletely dominant

A) mitochondrial

Consider an organism that is heterozygous for the genes Y and Z. If the two recessive alleles are on one chromosome, the genes are in _____.

A) cis

B) trans

C) the parental configuration

D) the recombinant configuration

A) cis

The first genetic linkage map was constructed in what organism?

A) bacteria

B) yeast

C) peas

D) fruit flies

D) fruit flies

A ____ is a group of genes or DNA sequences that are inherited together on the same chromosome.

A) haplotype

B) genotype

C) heteroplast

D) phenotype

A) haplotype

Progeny that exhibit a mixing of maternal and paternal alleles on a single chromosome are _____.

A) parentals

B) recombinants

C) haplotypes

D) mixed groups

B) recombinants

If the percent recombination between A and B is 12, between A and C is 4, and between B and C is 8, then the order of the genes on the chromosome is _____.

A) A - B - C

B) B - A - C

C) A - C - B

D) C - B - A

C) A - C - B

Given the gene sequence ABCDE, crossing over should occur most frequently between _____.

A) A - B

B) A - C

C) A - D

D) A - E

D) A - E

A field called ____ matches phenotypes to chromosomal variants.

A) linkage maps

B) haplotypes

C) cytogenetics

D) genome wide association studies

C) cytogenetics

____ describe(s) how several allele variants for a particular gene can exist in a given population. For example, for hair color there can be black, brown, red, blond hair, etc.

A) Complete dominance

B) Codominance

C) Incomplete dominance

D) Multiple alleles

D) Multiple alleles

____ allele combinations cause offspring to die early in development.

A) Epistatic

B) Variably expressive

C) Lethal

D) Codominant

C) Lethal

____ describes an allele combination in which the heterozygous phenotype is intermediate between those of the two homozygotes (for example, pink flowers are intermediate between red flowers and white flowers). The dominant allele does not completely mask the recessive allele.

A) Complete dominance

B) Codominance

C) Incomplete dominance

D) Epistasis

C) Incomplete dominance

____ describes an allele combination in which the heterozygous phenotype is distinct from, and is not an intermediate between, those of the two homozygotes (for example, AB blood type). Both alleles are equally expressed.

A) Complete dominance

B) Codominance

C) Incomplete dominance

D) Epistasis

B) Codominance

A man who is homozygous for type A blood has a child with a woman who is homozygous for type B blood. What is the probability that this child will have type AB blood?

A) 0%.

B) 25%

C) 50%

D) 100%

D) 100%

In humans, males are ____ since they have two different sex chromosomes.

A) homogametic

B) heterogametic

C) hermaphroditic

D) pseudohermaphroditic

B) heterogametic

Sexual identity is determined by the sex chromosome make-up of an individual only.

A) True

B) False

B) False

If the ____ gene on the ____ chromosome is activated, hormones steer the human development along a male route.

A) SRY; X

B) SRY; Y

C) XIST; X

D) sex; Y

B) SRY; Y

Recent DNA studies of Tsarina Alexandra and Crown Prince Alexei have shown that they probably suffered from which X-linked trait?

A) hemophilia A

B) hemophilia B

C) ichthyosis

D) colorblindness

B) hemophilia B

Pseudohermaphroditism caused by 5-alpha reductase deficiency leads to a _____.

A) female exterior, male interior, and male genotype

B) male exterior, female interior, and female genotype

C) female exterior, female interior, and female genotype

D) male exterior, male interior, and female genotype

A) female exterior, male interior, and male genotype

What would be the sex of an XXY individual?

A) male

B) female

C) hermaphrodite

D) mosaic

A) male

PAR1 and PAR2 on both tips of the Y chromosome are _____.

A) male specific regions

B) pseudoautosomal regions

C) sites of deletions

D) sex-determining regions

B) pseudoautosomal regions

What is the function of SRY?

A) transcription factor gene that stimulates male development

B) pseudoautosomal regions for meiosis

C) gene for testosterone production

D) cause of pseudohermaphroditism

A) transcription factor gene that stimulates male development

Evidence suggests that homosexuality is _____.

A) not inherited

B) partially inherited

C) completely inherited

D) completely environmental

B) partially inherited

An affected male and a normal female had four children: two affected daughters and two normal sons. Each of the affected daughters (and their normal husbands) produced affected sons and affected daughters. The couple's normal sons married normal women and had all normal children. What is the most likely mode of inheritance for this trait?

A) autosomal dominant

B) autosomal recessive

C) X-linked dominant

D) X-linked recessive

C) X-linked dominant

The probability that a male inherited his Y chromosome from his maternal grandfather is _____.

A) 0%

B) 25%

C) 50%

D) 100%

A) 0%

A female whose father was colorblind marries a normal male whose father was also colorblind. What is the probability that their son will be colorblind?

A) 0%

B) 25%

C) 50%

D) 75%

C) 50%

A female whose father was colorblind marries a normal male whose father was also colorblind. What is the probability that their daughter will be colorblind?

A) 0%

B) 25%

C) 50%

D) 75%

A) 0%

The SRY gene is present in which of the following?

A) XY female syndrome

B) XX male syndrome

C) Hermaphroditism

D) Pseudohermaphroditism

B) XX male syndrome

Which of the following genetic conditions is not sex-linked?

A) ichthyosis

B) colorblindness

C) sickle-cell anemia

D) hemophilia B

C) sickle-cell anemia

A woman whose brother has hemophilia is concerned about passing this trait to her offspring. If this woman has a son, what is the risk that her son will have hemophilia?

A) 1/8

B) 1/4

C) 1/2

D) 1

B) 1/4

Consider a sex-linked recessive trait. Which of the following crosses would produce males and females with different phenotypes?

A) homozygous normal female x normal male

B) affected female x affected male

C) affected female x normal male

D) heterozygous normal female x affected male

C) affected female x normal male

Can a male be a carrier for a sex-linked disease?

A) Yes, if the trait is recessive

B) Yes, if the male's father and mother were carriers

C) No, males have only a single copy of sex-linked genes

D) No way to predict

C) No, males have only a single copy of sex-linked genes

Males are ____ for X-linked traits.

A) homozygous

B) heterozygous

C) hemizygous

D) pseudozygous

C) hemizygous

Which of the following is incorrect for an X-linked recessive trait?

A) always expressed in the female

B) passed from heterozygote or homozygote mother to son

C) expressed in a female homozygote

D) affected female has an affected father and an affected or heterozygous mother

A) always expressed in the female

X-inactivation can account for individuals who _____.

A) are manifesting heterozygotes

B) show a mosaic pattern of expression

C) display a sex-limited trait

D) a and b

D) a and b

How many Barr bodies would be observed in the nucleus of an XXY individual?

A) 0

B) 1

C) 2

D) 3

B) 1

Individuals with three copies of most autosomes do not survive. Individuals with an extra X chromosome, however, survive with relatively mild (compared to autosomal abnormalities) consequences. Why?

A) The X chromosome contains few genes while autosomes contain a large number.

B) The extra X chromosome(s) are inactivated.

C) The X chromosome determines sex only.

D) None of the above

B) The extra X chromosome(s) are inactivated

Calico cats have large patches of coat color. What can we conclude about the timing of X-inactivation?

A) It occurred early.

B) It occurred late.

C) It occurred both early and late.

D) No relationship exists.

A) It occurred early.

The majority of calico cats are female. However, a few rare males are observed. What is the genotype of a male calico cat?

A) XBXb

B) XBY

C) XbYY

D) XBXbY

D) XBXbY

Pattern baldness is a ____ trait.

A) sex-linked

B) sex-limited

C) sex-influenced

D) Y-linked

C) sex-influenced

A ____ affects body parts or functions present in only one gender.

A) sex-linked trait

B) trait determined by mitochondrial DNA

C) sex-limited trait

D) sex-influenced trait

C) sex-limited trait

Beard growth and pregnancy in humans are examples of ____ traits.

A) sex-linked

B) sex-influenced

C) sex-limited

D) Y-linked

C) sex-limited

Which item correctly represents a female who is homozygous recessive for an X-linked trait?

A) XBXB

B) XBXb

C) XbXb

D) XbY

C) XbXb

Prader-Willi Syndrome and Angelman Syndrome are both associated with deletions of the same bands from the long arm of chromosome 15. However, the physical expression associated with each disorder is very different. This is an example of _____.

A) genomic imprinting

B) nuclear inheritance

C) Mendelian inheritance

D) heteroplasmy

A) genomic imprinting

Each of the following statements describes Y-linked inheritance EXCEPT:

A) Traits are transmitted from father to son.

B) There are no affected females.

C) Traits that involve infertility are not transmitted.

D) Traits are transmitted from mother to son.

D) Traits are transmitted from mother to son.

A human male inherits X-linked traits from _____.

A) his mother only

B) his father only

C) both his mother and father

D) Males do not have X-linked traits.

A) his mother only

Which item correctly represents a male who inherits an X-linked dominant trait?

A) XBY

B) 2 XBYB

C) XbY

D) XBXB

A) XBY

A human female inherits X-linked traits from _____.

A) her mother only

B) her father only

C) both her mother and father

D) Females do not have X-linked traits.

C) both her mother and father

Human height is an example of a(n) ____ trait.

A) autosomal

B) sex-linked

C) epistatic

D) polygenic

D) polygenic

Which of the following is not an example of a multifactorial trait?

A) cystic fibrosis

B) skin color

C) height

D) fingerprint patterns

A) cystic fibrosis

Can a child have darker skin than either of his or her parents?

A) Yes

B) No

C) No basis for determination

A) Yes

How many markers need to be included in a genome-wide association study to achieve statistical significance?

A) 1 - 10

B) 10 - 100

C) 100 - 1,000

D) 100,000

D) 100,000

Which of the following polygenic characteristics is probably a pure polygenic trait - one with no environmental input?

A) skin color

B) height

C) eye color

D) fingerprint patterns

C) eye color

Heritability is a measurement that estimates the proportion of _____.

A) genetic variation in a group that can be attributed to the environment

B) phenotypic variation in an individual that can be attributed to genes

C) phenotypic variation in a certain population that is due to genetic differences within the population

D) None of the above

C) phenotypic variation in a certain population that is due to genetic differences within the population

Siblings share ____% of their genes while fraternal twins share ____% and identical twins share ____% of their genes (on average).

A) 50; 50; 50

B) 50; 100; 100

C) 100; 100; 100

D) 50; 50; 100

D) 50; 50; 100

In humans, obesity has a heritability of _____.

A) 25%

B) 55%

C) 75%

D) 90%

C) 75%

A more informative way to assess the genetic component of a multifactorial trait is to study ____ who were separated at birth, then raised in very different environments.

A) adopted children

B) monozygotic (MZ) twins

C) dizygotic (DZ) twins

D) cousins

B) monozygotic (MZ) twins

Geneticists calculate the ____ of a trait, or the degree to which it is inherited, as the percentage of pairs in which both twins express the trait.

A) heritability

B) coefficient of relationship

C) concordance

D) empiric risk

C) concordance

A trait more often present in both members of MZ twin pairs than in both DZ twin pairs has a large _____.

A) environmental component

B) inherited component

C) random component

D) No conclusions can be drawn in this case.

B) inherited component

The risk of recurrence of a trait based on its known incidence in a particular population refers to _____.

A) the empiric risk

B) the correlation coefficient

C) heritability

D) concordance

A) the empiric risk

The concordance between identical twins for body weight was calculated to be 0.42. What is the heritability of body weight?

A) 0

B) 0.21

C) 0.42

D) 0.84

C) 0.42

A coefficient of relatedness of 100% indicates _____.

A) fraternal twins

B) a parent to child relationship

C) a cousin to cousin relationship

D) monozygotic twins

D) monozygotic twins

Characteristics shared by adopted children and their biological parents are mostly ____ while their similarities with adoptive parents reflect ____ influences.

A) environmental; heritable

B) genetic; environmental

C) genetic; heritable

D) plastic; immutable

B) genetic; environmental

Assume that three pairs of alleles with no environmental modification control height in humans. In this model, each dominant allele contributes four inches to a base height of four feet. What is the range of heights possible in this population?

A) 0 - 2 feet

B) 4 - 5 feet

C) 2 - 4 feet

D) 4 - 6 feet

D) 4 - 6 feet

Using the information from question 17, if a woman of the minimum specified height marries a man of intermediate height, what is the maximum achievable height for a child they produce?

A) 3 feet

B) 4 feet

C) 5 feet

D) 6 feet

C) 5 feet

In general, empiric risk for an individual increase with _____.

A) the severity of the disorder

B) the number of affected family members

C) how closely related the person is to affected individuals

D) All of the above

D) All of the above

A higher heritability would be found for a trait in a population that is _____.

A) homozygous for genes affecting the trait

B) in a uniform environment

C) heterozygous for genes affecting the trait

D) in a heterogeneous environment

B) in a uniform environment

Genes that control lipid metabolism and blood clotting, blood pressure, and cell adhesion contribute to cardiovascular health.

A) True.

B) False.

A) True.

Genome-wide association studies _____.

A) make use of SNP mapping

B) relate sequence patterns to the probability of developing a particular disorder

C) are more powerful than heritability studies

D) All of the above are true in regard to association studies.

D) All of the above are true in regard to association studies.

Genetic variance for a multifactorial polygenic trait is usually due to the additive effects of many ____ alleles of different genes.

A) dominant

B) recessive

C) lethal

D) similar

B) recessive

____ seek correlations between SNP patterns and phenotypes in large groups of individuals.

A) Karyotype analyses

B) Heritability calculations

C) Genome-wide association studies

D) Pedigree analyses

C) Genome-wide association studies

Which of the following is a controllable factor in assessing risk factors for cardiovascular disease?

A) stress

B) lipid metabolism genes

C) lipoprotein lipase genes

D) fibrinogen genes

A) stress

A gene encoding a protein called ____ is involved in lipid metabolism and cardiovascular disease.

A) leptin

B) dopamine

C) lipoprotein lipase

D) None of the above

C) lipoprotein lipase

Which of the following proteins affects body weight?

A) apolipoprotein

B) dopamine

C) leptin

D) fibrinogen

C) leptin

Studies of the Pima Indians have helped identify environmental influences for which of these?

A) cancer

B) cardiovascular disease

C) obesity

D) diabetes

C) obesity

Ghrelin is produced by what organ?

A) stomach

B) liver

C) pancreas

D) hypothalamus

A) stomach

Leptin is secreted by _____ cells to influence the action of the _____.

A) liver; stomach

B) fat; hypothalamus

C) hypothalamus; intestine

D) pancreas; liver

B) fat; hypothalamus

Populations that suddenly become sedentary and switch to a fatty diet reflect ____ influences on body weight.

A) genetic

B) environmental

C) association

D) concordance

B) environmental

A ____ is determined by more than one gene and varies continuously in expression.

A) dominant allele

B) population

C) polygenic trait

D) recessive allele

C) polygenic trait

Multifactorial traits reflect _____.

A) environmental influences only

B) genetic influences only

C) both environmental and genetic influences

D) neither environmental nor genetic influences

C) both environmental and genetic influences