Question 1

Which situation is an example of modifier gene action?

Accepted Answer

A)  A mother and father both have type O blood, and their son is born with type B blood.
B)  Two children in the same family both have sickle cell disease, but one child has more severe symptoms than the other.
C)  Monozygotic twins separated at birth and raised in two different countries are of different heights (3 inches)  and different weights (25 pounds) .
D)  A woman who has a gene mutation for diabetes mellitus type 2 delays the onset of the disease by exercising and maintaining a normal weight.E) A) and D)
F) All of the above

Question 2

An infant with type B blood is born to parents who both have type O blood. What genetic action or phenomenon is responsible for this unusual blood type expression?

Accepted Answer

A)  Decreased penetrance of a dominant trait
B)  Variable expressivity of a recessive trait
C)  Inactivation of both parents' X chromosomes
D)  Failure of one parent's blood-type gene alleles to segregateE) None of the above
F) C) and D)

Question 3

Which common health problem has the highest heritability estimate?

Accepted Answer

A)  Hypertension
B)  Peptic ulcer disease
C)  Congenital heart disease
D)  Schizophrenic behaviorE) B) and C)
F) A) and D)

Question 4

When calculating the recurrence risk for a complex, possibly polygenic disorder with a couple who already have one child with the disorder, which additional factorhasthe greatest impact on increasing this risk?

Accepted Answer

A)  The child with the disorder is male, and the overall incidence of the disorder is twice as high in males than females.
B)  Both the mother and the father are heavily exposed to a variety of chemicals in their workplaces.
C)  The father has a nephew with a mild form of the same disorder.
D)  The mother has a brother who also has the same disorder.E) A) and D)
F) A) and C) D

Question 5

What is the risk for a person to inherit an autosomal-dominant genetic disease-causing allele from a parent who is heterozygous if the disorder has a penetrance factorof 75%?

Accepted Answer

A)  100%
B)  75%
C)  50%
D)  25%E) B) and C)
F) All of the above

Question 6

Is it possible for two parents with achondroplasia to have a child who is of normal stature?

Accepted Answer

A)  Yes, because the disorder is autosomal dominant, and if both parents are heterozygous, the child could inherit two normal stature gene alleles.
B)  Yes, if the parent who is homozygous for the gene mutation demonstrates variable expressivity of the health problem.
C)  No, because the disorder is autosomal recessive, and the child can only inherit two mutated gene alleles for the health problem.
D)  No, because homozygosity for this health problem is lethal.E) A) and D)
F) B) and C)

Question 7

What is the most likely explanation for the expression of responses related to pleiotropy?

Accepted Answer

A)  The same gene may have more than one chromosome locus.
B)  The protein coded for by the single gene is an important component of more than one tissue.
C)  The silencing of a gene allele inherited from one parent is expressed differently depending on which parent contributed the silenced allele.
D)  The same disorder may have an autosomal-dominant inheritance pattern, an autosomal-recessive inheritance pattern, and an X-linked-recessive inheritance pattern.E) A) and B)
F) A) and C)

Question 8

Which statement reflects the criterion for autosomal-dominant transmission of single-gene traits?

Accepted Answer

A)  The risk for a person who is homozygous for the trait to transmit the trait to his or her children is 100% with each pregnancy.
B)  The trait often remains unexpressed within a kindred for many generations until a change in environment promotes its expression.
C)  Males in a kindred are more likely to express the trait when the mother has the trait, and females in a kindred are more likely to express the trait when the father has the trait.
D)  Females in a kindred are more likely to express the trait when the mother has the trait, and males in a kindred are more likely to express the trait when the father has the trait.E) All of the above
F) A) and B) A

Question 9

With which type of inheritance pattern does the trait or disorder usually first appear among siblings rather than in parents of affected children?

Accepted Answer

A)  Autosomal dominant
B)  Autosomal recessive
C)  X-linked dominant
D)  CodominantE) B) and C)
F) A) and D)

Question 10

A woman (Adele)  has three daughters (Barbara, Brenda, Beverly)  with a man (Adam)  who is color-blind. Barbara has a daughter (Carol)  and a son (Cliff)  who havenormal color vision. Brenda has no children. Beverly has two sons (Carl, Charlie)  who are both color-blind. To which genetic generation do Carl and Charlie belong?

Accepted Answer

A)  P1
B)  P2
C)  F1
D)  F2E) C) and D)
F) B) and D)

Question 11

Which situation most closely represents an example of "regression to the mean"?

Accepted Answer

A)  Two hearing-impaired parents produce a child who has normal hearing.
B)  A 40-year-old man whose father developed type 2 diabetes mellitus at age 50 is diagnosed with the disorder.
C)  The three children of a mother who has an intelligence quotient (IQ)  of 170 all have IQs in the 110 to 120 range.
D)  A child whose biologic parents are thin is adopted by a family whose members are obese and eventually becomes overweight.E) A) and B)
F) None of the above C

Question 12

Which trait or disorder has both an autosomal-dominant form and an autosomal-recessive form?

Accepted Answer

A)  Widow's peak
B)  Diabetes mellitus type 2
C)  Polycystic kidney disease
D)  Taste sensitivity to phenylthiocarbamate (PT
C)  E) A) and C)
F) C) and D)

Question 13

What is the significance of a shift to the left in the threshold value of liability in a threshold of liability model for the expression of a complex health problemwith genetic influences?

Accepted Answer

A)  The threshold required for disease expression increases as the population ages.
B)  The number of affected individuals within the population has decreased.
C)  The population examined for the potential problem is getting larger.
D)  The threshold required for disease expression is lower.E) B) and D)
F) A) and D)

Question 14

Which statement regarding inheritance of an autosomal-dominant gene allele with known variability in expressivity is true?

Accepted Answer

A)  A person with low expressivity of the trait has a higher probability of having a child who does not express the trait at all.
B)  A person with high expressivity of the trait has a greater risk of having a child who expresses the trait to an even greater degree.
C)  The degree of expressivity of a given autosomal-dominant trait with known variability cannot be predicted by analyzing parental expression.
D)  The degree of expressivity of a given autosomal-dominant trait with known variability is greater when the transmitting parent is the same sex as the child.E) A) and B)
F) C) and D)

Question 15

Mating of a female rabbit with a long tongue with a male rabbit that had a short tongue resulted in 12 offspring. Two had long tongues, two had short tongues,and eight had medium-length tongues. Which allele combinations explains the tongue lengths of the offspring?

Accepted Answer

A)  Short tongue dominant; long tongue recessive
B)  Short tongue recessive; long tongue dominant
C)  Short tongue dominant; long tongue dominant
D)  Short tongue dominant; long tongue X-linked recessiveE) B) and D)
F) All of the above

Question 16

Why are dizygotic twins less likely to show concordance for a monogenic trait than monozygotic twins?

Accepted Answer

A)  Dizygotic twins share fewer allele sequences in common than monozygotic twins.
B)  It is possible for dizygotic twins to have different fathers, and monozygotic twins always have the same father.
C)  Gene expression in monozygotic twins is less influenced by environmental factors than that of dizygotic twins.
D)  Because of their identical appearance, monozygotic twins are more likely to be raised together and share a common environment than are dizygotic twins.E) B) and C)
F) A) and D)

Question 17

Which genetic disorder has both an autosomal-dominant and an autosomal-recessive form?

Accepted Answer

A)  Syndactyly
B)  Phenylketonuria
C)  Long QT syndrome
D)  Retinitis pigmentosaE) A) and D)
F) B) and D)

Question 18

Which statement or condition best reflects multifactorial inheritance?

Accepted Answer

A)  A mutation in a single gene results in the expression of problems in a variety of tissues and organs.
B)  The susceptibility to a problem is an inherited trait, but development of the problem is related to environmental conditions.
C)  A mutated gene is inherited, but the results of expression of that gene are not evident until middle or late adulthood.
D)  Several genes are responsible for the mechanism of hearing, and a mutation in any one of them results in hearing impairment.E) A) and B)
F) A) and C)

Question 19

Which statement is a criterion for an autosomal-dominant pattern of inheritance of a specific trait or characteristic that is highly penetrant?

Accepted Answer

A)  Carriers for the trait may express it but do not necessarily express the trait.
B)  Unaffected family members do not transmit the trait to their children.
C)  Genotypes of individuals expressing the trait must be homozygous.
D)  The trait appears only among male offspring of female carriers.E) A) and B)
F) B) and C)

Question 20

If a man with classic hemophilia (X-linked recessive)  has children with a woman who is a carrier for the disorder, what is the expected risk pattern?

Accepted Answer

A)  All sons will be unaffected; all daughters will be carriers.
B)  All sons will be carriers; all daughters will be affected.
C)  All sons have a 50% risk of the disorder; daughters will all either be affected or carriers.
D)  All sons will be carriers; daughters have a 50% chance of being a carrier and a 50% chance of being unaffected.E) B) and C)
F) A) and B)

Exam 4: Patterns of Inheritance

Which situation is an example of modifier gene action?

Correct Answer
verified

An infant with type B blood is born to parents who both have type O blood. What genetic action or phenomenon is responsible for this unusual blood type expression?

Correct Answer
verified

Which common health problem has the highest heritability estimate?

Correct Answer
verified

When calculating the recurrence risk for a complex, possibly polygenic disorder with a couple who already have one child with the disorder, which additional factorhasthe greatest impact on increasing this risk?

Correct Answer
verified
D

What is the risk for a person to inherit an autosomal-dominant genetic disease-causing allele from a parent who is heterozygous if the disorder has a penetrance factorof 75%?

Correct Answer
verified

Is it possible for two parents with achondroplasia to have a child who is of normal stature?

Correct Answer
verified

What is the most likely explanation for the expression of responses related to pleiotropy?

Correct Answer
verified

Which statement reflects the criterion for autosomal-dominant transmission of single-gene traits?

Correct Answer
verified
A

With which type of inheritance pattern does the trait or disorder usually first appear among siblings rather than in parents of affected children?

Correct Answer
verified

Correct Answer
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Which situation most closely represents an example of "regression to the mean"?

Correct Answer
verified
C

Which trait or disorder has both an autosomal-dominant form and an autosomal-recessive form?

Correct Answer
verified

What is the significance of a shift to the left in the threshold value of liability in a threshold of liability model for the expression of a complex health problemwith genetic influences?

Correct Answer
verified

Which statement regarding inheritance of an autosomal-dominant gene allele with known variability in expressivity is true?

Correct Answer
verified

Mating of a female rabbit with a long tongue with a male rabbit that had a short tongue resulted in 12 offspring. Two had long tongues, two had short tongues,and eight had medium-length tongues. Which allele combinations explains the tongue lengths of the offspring?

Correct Answer
verified

Why are dizygotic twins less likely to show concordance for a monogenic trait than monozygotic twins?

Correct Answer
verified

Which genetic disorder has both an autosomal-dominant and an autosomal-recessive form?

Correct Answer
verified

Which statement or condition best reflects multifactorial inheritance?

Correct Answer
verified

Which statement is a criterion for an autosomal-dominant pattern of inheritance of a specific trait or characteristic that is highly penetrant?

Correct Answer
verified

If a man with classic hemophilia (X-linked recessive) has children with a woman who is a carrier for the disorder, what is the expected risk pattern?

Correct Answer
verified

Exam 4: Patterns of Inheritance

Which situation is an example of modifier gene action?

Correct AnswerverifiedShow Answer

An infant with type B blood is born to parents who both have type O blood. What genetic action or phenomenon is responsible for this unusual blood type expression?

Correct AnswerverifiedShow Answer

Which common health problem has the highest heritability estimate?

Correct AnswerverifiedShow Answer

When calculating the recurrence risk for a complex, possibly polygenic disorder with a couple who already have one child with the disorder, which additional factorhasthe greatest impact on increasing this risk?

Correct AnswerverifiedD

What is the risk for a person to inherit an autosomal-dominant genetic disease-causing allele from a parent who is heterozygous if the disorder has a penetrance factorof 75%?

Correct AnswerverifiedShow Answer

Is it possible for two parents with achondroplasia to have a child who is of normal stature?

Correct AnswerverifiedShow Answer

What is the most likely explanation for the expression of responses related to pleiotropy?

Correct AnswerverifiedShow Answer

Which statement reflects the criterion for autosomal-dominant transmission of single-gene traits?

Correct AnswerverifiedA

With which type of inheritance pattern does the trait or disorder usually first appear among siblings rather than in parents of affected children?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Which situation most closely represents an example of "regression to the mean"?

Correct AnswerverifiedC

Which trait or disorder has both an autosomal-dominant form and an autosomal-recessive form?

Correct AnswerverifiedShow Answer

What is the significance of a shift to the left in the threshold value of liability in a threshold of liability model for the expression of a complex health problemwith genetic influences?

Correct AnswerverifiedShow Answer

Which statement regarding inheritance of an autosomal-dominant gene allele with known variability in expressivity is true?

Correct AnswerverifiedShow Answer

Mating of a female rabbit with a long tongue with a male rabbit that had a short tongue resulted in 12 offspring. Two had long tongues, two had short tongues,and eight had medium-length tongues. Which allele combinations explains the tongue lengths of the offspring?

Correct AnswerverifiedShow Answer

Why are dizygotic twins less likely to show concordance for a monogenic trait than monozygotic twins?

Correct AnswerverifiedShow Answer

Which genetic disorder has both an autosomal-dominant and an autosomal-recessive form?

Correct AnswerverifiedShow Answer

Which statement or condition best reflects multifactorial inheritance?

Correct AnswerverifiedShow Answer

Which statement is a criterion for an autosomal-dominant pattern of inheritance of a specific trait or characteristic that is highly penetrant?

Correct AnswerverifiedShow Answer

If a man with classic hemophilia (X-linked recessive) has children with a woman who is a carrier for the disorder, what is the expected risk pattern?

Correct AnswerverifiedShow Answer

Correct Answer
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D

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A

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C

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