Common Adult-onset Disorders

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Question 1

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Multiple Choice

Why are complex or multifactorial disorders more commonly expressed among adults than among children?

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As adults age, there is more time for environmental factors to influence the expression of a genetic disorder.

Gene expression in adults is greater than in childhood as a result of age-related amplification of gene copy numbers.

Children have better DNA repair mechanisms than adults and are more likely to correct a predisposition for a complex disorder.

In order for a complex or multifactorial disorder to be expressed in childhood, the child must be homozygous for the genetic mutation.

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Question 2

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Multiple Choice

Why is predictive testing for Huntington disease avoided for a 4-year-old child who has one grandparent with the disorder?

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Unless one of the parents is positive for the gene mutation, a negative finding would be noninformative.

The Huntington disease mutation is poorly penetrant and may never be expressed even when inherited.

A 4-year-old child cannot understand or participate in the genetic counseling process.

There are no effective primary or secondary prevention strategies for this disorder.

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Question 3

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Multiple Choice

What is the best definition of the term compound heterozygous?

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A person who has two different mutated alleles for an autosomal-recessive disorder

A person whose expression of an autosomal-recessive disorder is modified by silencing of one allele

A person who expresses a genetic disorder having different mutations on two nonhomologous chromosomes

A person having a complex disorder in which there is unequal influence of genetic and environmental contributions

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Question 4

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Multiple Choice

Which relatively common adult-onset disorder or health problem is the result of a mutation in a single gene?

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Type 2 diabetes

Multiple sclerosis

Hereditary hemochromatosis

Age-related macular degeneration

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Question 5

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Multiple Choice

Your patient's family comes from Ireland. Both her parents are carriers of gene mutations causing hereditary hemochromatosis (HFE-HHC). What is your patient'srisk of having the clinical signs of this disorder?

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HHC is an autosomal-recessive condition; the risk is 25%.

HHC has incomplete penetrance; we cannot accurately predict the clinical risk.

HHC is a complex trait; we cannot accurately predict the clinical risk.

HHC is an autosomal-dominant trait; the risk is 50%.

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Question 6

Multiple Choice

Why do the clinical signs and symptoms of hereditary hemochromatosis not appear until middle adulthood?

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The adult over 50 has had more exposures to environmental insults over time.

Prolonged dietary exposure to toxins produces clinical symptoms.

Hereditary hemochromatosis has age-related penetrance.

Stored iron builds up over time, causing organ damage.

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Question 7

Multiple Choice

Why are women usually older than men before symptoms of hereditary hemochromatosis manifest?

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Women have a counterbalancing normal gene on their second X chromosome.

Women lose some iron with normal menstruation during childbearing years.

Men have a larger muscle mass and more iron-storing capability than women.

Men have greater expression of the gene for hemoglobin than do women.

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Question 8

Multiple Choice

If a man with hereditary hemochromatosis has children with a woman who is a carrier for the disorder, what is the expected risk pattern?

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All sons will be affected; all daughters will be carriers.

Daughters have a 50% risk for being affected; all sons will either be affected or carriers.

Each child of either gender has a 50% risk of being a carrier and a 50% risk of having the disease.

Each child of either gender has a 50% risk of being a carrier, a 25% risk of having the disease, and a 25% risk of neither being a carrier nor having the disease.

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Question 9

Multiple Choice

What do each of the genes involved in maturity-onset diabetes of the young (MODY) have in common?

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They are all located on the long arm of chromosome 6.

They each play a role in the metabolism of glucose, or insulin action and release.

Although they are of different sizes, they all contain the same exon and intron sequences.

The genes that cause MODY are expressed only in the young and suppressed during adulthood.

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Question 10

Multiple Choice

A fasting blood glucose sample indicates that your 24-year-old male patient has hyperglycemia that was not present during a test 6 weeks ago. What is the mostlikely cause of this?

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Type 1 diabetes mellitus

Type 2 diabetes mellitus

Maturity-onset diabetes of the young (MODY)

Gestational diabetes mellitus

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Question 11

Multiple Choice

Which type of maturity-onset diabetes of the young (MODY) is the most common?

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MODY-1

MODY-2

MODY-3

MODY-4

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Question 12

Multiple Choice

Which type of diabetes has a slow onset and is often diagnosed in North American only when a complication is present?

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Type 1 diabetes mellitus

Type 2 diabetes mellitus

Maturity-onset diabetes of the young (MODY)

Gestational diabetes mellitus

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Question 13

Multiple Choice

What can be interpreted about type 2 diabetes mellitus in monozygotic twins when it affects only one twin 70% of the time and affects both twins 30% of the time?

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The trait is recessive.

Mutation repair is incompletely penetrant.

Nongenetic factors can influence expression.

Homologous genes can undergo chromatid exchanges.

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Question 14

Multiple Choice

Which condition or factor most strongly supports a genetic basis for the development of type 2 diabetes mellitus?

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Type 2 diabetes occurring in two cousins before age 30 years

The disease developing in a person whose parents also have type 2 diabetes

The fact that the incidence of disease concordance is higher in dizygotic twins than in monozygotic twins

The fact that type 2 diabetes is more prevalent in one city than it is in another city of similar size

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Question 15

Multiple Choice

Which statement best explains the "thrifty genotype" for the high incidence of type 2 diabetes?

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The person with a thrifty genotype has an efficient metabolism that generates more energy from less food and is more likely to survive famine.

The person with a thrifty genotype conserves the energy lost from the body as heat and requires less rest to perform the same amount of work.

The person with a thrifty genotype stores energy rather than expends energy so that more energy is available for survival when food is scarce.

The person with a thrifty genotype feels satiety with smaller amounts of food and is less likely to become obese, thus increasing longevity.

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Question 16

Multiple Choice

Which genetic disorder is associated with an increased risk for type 2 diabetes?

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Achondroplasia

Down syndrome

Huntington disease

Hereditary hemochromatosis

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Question 17

Multiple Choice

What is the inheritance pattern for ?-1 antitrypsin (ATT) deficiency?

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Autosomal dominant

Autosomal recessive

Autosomal codominant

Sex-linked recessive

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Question 18

Multiple Choice

A 31-year-old man has been diagnosed with chronic obstructive pulmonary disease (COPD) as a result of being homozygous for the ZZ mutation of the ?-1 antitrypsin (AAT)gene alleles. His wife has been tested and has the MM genotype on her AAT gene alleles. The man is worried that his three children may eventually develop COPD. What is your best response?

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"Because your wife does not have the mutation, and neither of your parents has the disease, your children will not be affected."

"Because your wife is not affected and is not a carrier, your children will have normal levels of AAT, and their risk is the same as for the general population."

"Because you have the mutations, and your wife does not, your son will be at an increased risk for developing COPD, but your daughter will only be a carrier."

"Because your children will each have only one mutated gene allele, their risk for COPD is primarily dependent on chronic environmental exposure to inhalation irritants."

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Question 19

Multiple Choice

Which factor is consistent with multifactorial (complex) genetic disease?

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Expression of the trait often involves mutations in several genes.

Monozygotic (identical) twin concordance is 100%.

Genotype consistently predicts phenotype.

It tends to be autosomal dominant.

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Question 20

Multiple Choice

An obese patient (body mass index of 35) states, "There is no point in changing how I eat because it is all genetics anyway." What is the best response?

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"Even with a large genetic component, obesity can be reduced through a sensible diet and exercise."

"Let's gather some more family history about body height, weight, and eating patterns."

"You are right; you can't change your genes. There is no point in dieting."

"With your genetics, your best bet would be a low-carb Atkins-type diet."

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