Genetics Chapter 6

Which of the statements is true? a) Dizygotic twins, on average, have 50% of their genes in common, whereas monozygotic twins have 100% of their genes in common. b) Dizygotic twins usually look more alike than do monozygotic twins. c) Dizygotic twins must be of the same gender, but monozygotic twins can be of different genders. d) The tendency to produce monozygotic twins often runs in families and is influenced by genetic factors, whereas genetic factors seem to have no impact on the occurrence of dizygotic twins. e) Monozygotic twins develop from one egg fertilized by two sperm, whereas dizygotic twins develop from two eggs fertilized by one sperm.

a) Dizygotic twins, on average, have 50% of their genes in common, whereas monozygotic twins have 100% of their genes in common.

Which statement is incorrect about adoption studies? a) Similarities between adopted persons and their adoptive parents can generally be attributed to genetic factors. b) Similarities between adopted persons and their adoptive parents can generally be attributed to environmental factors. c) Adoption studies were used to show a genetic basis for schizophrenia. d) These studies can be used to distinguish the effect of genes and environment on characteristics. e) Similarities between adopted persons and their biological parents can generally be attributed to genetic factors.

a) Similarities between adopted persons and their adoptive parents can generally be attributed to genetic factors.

What is a proband? a) an affected individual in a pedigree who brings the family to the attention of the medical community b) an individual who undergoes newborn screening for a genetic disorder that can be treated if detected early c) a woman who becomes pregnant and requests genetic counseling d) an individual who is found to be carrying a recessive mutant allele during a heterozygote screening program e) the karyotype of a normal fetus obtained through amniocentesis

a) an affected individual in a pedigree who brings the family to the attention of the medical community

A ________________ is a pictorial representation of a family history that outlines the inheritance of specific characteristics. a) pedigree b) carrier c) consanguinity d) genealogy tree e) proband

a) pedigree

Assume that the concordance value for a particular trait is 85% for both monozygotic and dizygotic twins. What can be concluded about this trait? a) It is caused by environmental factors in dizygotic twins but by genetic factors in monozygotic twins. b) It is likely caused almost exclusively by environmental factors. c) It is likely caused almost exclusively by genetic factors. d) It is caused by both genetic factors and environmental factors. e) It is caused by genetic factors in dizygotic twins but by environmental factors in monozygotic twins.

b) It is likely caused almost exclusively by environmental factors.

A direct‑to‑consumer genetic test can be best characterized by which description? a) a noninvasive procedure that allows the detection and analysis of fetal cells in maternal blood b) a genetic test that can be purchased without the involvement of a health professional c) a genetic test that allows the karyotype of a fetus to be examined d) the most accurate genetic test currently available e) a genetic test that involves testing members of a particular population to determine those that are heterozygous for a recessive genetic disorder

b) a genetic test that can be purchased without the involvement of a health professional

If a man exhibits a Y‑linked trait, what proportion of his sons should also be affected? a) one‑half b) all c) three‑fourths d) one‑fourth e) none

b) all

Based on the pedigree shown on the animation, which individuals give a clue on how to eliminate the Y‑linked trait? a) II‑1 and II‑2 b) IV‑7 and IV‑8 c) III‑5; III‑6; III‑7; III‑8 d) II‑2 and II‑7 e) II‑6 and IV-9

c) III‑5; III‑6; III‑7; III‑8

A maternal blood‑screening test carried out during a pregnancy indicates a level of α‑fetoprotein that is significantly higher than normal. What might this result indicate? a) The fetus has phenylketonuria. b) The fetus has a chromosome abnormality. c) The fetus has a neural‑tube defect. d) The fetus has Down syndrome. e) The fetus is heterozygous for a genetic disorder.

c) The fetus has a neural‑tube defect.

Consider the list. pattern shows sex bias with more affected males than females affected sons are usually born to unaffected mothers tends to skip a generation never passes from father to son all daughters of affected fathers are carriers Which of the inheritance patterns best fits the pedigree characteristics described in the list? a) Y‑linked b) autosomal recessive c) X‑linked recessive d) X‑linked dominant e) autosomal dominant

c) X‑linked recessive

Which term is not used to facilitate the study of human genetics? a) twin studies b) pedigrees c) controlled crosses d) adoption studies

c) controlled crosses

A trait shows X‑linked dominant inheritance. A normal daughter of an affected mother marries a normal man. What proportion of their children will be affected? a) one‑half b) one‑fourth c) none d) all e) three‑fourths

c) none

Which of the statements cannot occur with X‑linked dominant inheritance for a rare trait? a) An affected woman can have a normal daughter. b) An affected woman can pass on the trait to both sons and daughters. c) An affected man can pass on the trait to his daughter. d) An affected man can pass on the trait to his son. e) An affected man can have a normal son.

d) An affected man can pass on the trait to his son.

Which of the statements about X‑linked recessive traits is false? a) Affected females almost always have an affected father. b) They often skip generations. c) Males are more commonly affected than females. d) They can be passed from father to son. e) Affected individuals often have phenotypically normal parents.

d) They can be passed from father to son.

Consider the list. usually appears in both sexes with equal frequency both parents can transmit the trait to their offspring affected offspring most commonly have an affected parent unaffected parents do not transmit the trait does not skip generations Which of the inheritance patterns best fits the pedigree characteristics described in the list? a) X‑linked recessive b) Y‑linked c) X‑linked dominant d) autosomal dominant e) autosomal recessive

d) autosomal dominant

A trait appears in both men and women with equal frequency, and offspring can inherit the trait from the mother or the father. All affected individuals have at least one affected parent. This trait is a) Y‑linked. b) X‑linked dominant. c) X‑linked recessive. d) autosomal dominant. e) autosomal recessive.

d) autosomal dominant.

Which statement concerning chorionic villus sampling is false? a) A karyotype can be made from fetal cells. b) The fetal cells obtained usually do not need to be cultured before analysis. c) It is usually performed between the 10th and 12th weeks of pregnancy. d) Biochemical analyses can be performed on fetal cells. e) It has fewer complications than does amniocentesis.

e) It has fewer complications than does amniocentesis.

Consider the list. both sexes are usually affected, but often more females than males are affected affected fathers will pass the trait onto all their daughters affected mothers will pass the trait onto half of their sons and half of their daughters does not skip generations Which of the inheritance patterns best fits the pedigree characteristics described in the list? a) autosomal recessive b) autosomal dominant c) X‑linked recessive d) Y‑linked e) X-linked dominant

e) X-linked dominant

Consider the list. affected offspring are usually born to unaffected parents usually appears in both sexes with equal frequency tends to skip a generation appears more frequently among the children of consanguine (first cousin) marriages Which of the inheritance patterns best fits the pedigree characteristics described in the list? a) Y‑linked b) X‑linked dominant c) autosomal dominant d)X‑linked recessive e) autosomal recessive

e) autosomal recessive

What is the term that refers to a pair of twins where one twin has the trait under consideration and the other twin does not? a) consanguine b) concordant c) proband d) dizygotic e) discordant

e) discordant

A male with a rare autosomal dominant trait marries a phenotypically normal woman. What proportion of their children should show the trait? a) one‑fourth b) three‑fourths c) all d) none e) one‑half

e) one‑half

What is the main reason that geneticists devote so many resources to studying genetics in humans?

they want to understand the many aspects of human health, physiology, and behavior that are influenced by genes