Question 1

Which condition or factor most strongly supports a genetic basis for development of type 2 diabetes mellitus?&#10;A)Type 2 diabetes occurring in two cousins before age 30 years&#10;B)The disease developing in a person whose parents also have type 2 diabetes&#10;C)The incidence of disease concordance is higher in dizygotic twins than in monozygotic twins&#10;D)The fact that type 2 diabetes is more prevalent in one city than it is in another similar size city

Accepted Answer

The presence of a family history of type 2 diabetes strongly suggests a genetic basis for the development of the disease. Studies have shown that having a first-degree relative with type 2 diabetes increases an individual's risk of developing the disease by 3-5 times compared to those without a family history. While other factors such as lifestyle and environmental influences also play a role, the familial clustering of the disease strongly supports a genetic component.

Question 2

Why are complex or multifactorial disorders more commonly expressed among adults than among children?&#10;A)As adults age there is more time for environmental factors to influence the expression of a genetic disorder.&#10;B)Gene expression in adults is greater than in childhood as a result of age-related amplification of gene copy numbers.&#10;C)Children have better DNA repair mechanisms than adults and are more likely to correct a predisposition for a complex disorder.&#10;D)In order for a complex or multifactorial disorder to be expressed in childhood,the child must be homozygous for the genetic mutation.

Accepted Answer

Complex or multifactorial disorders often require the interaction of both genetic predisposition and environmental factors for their expression. As adults age, there is more time for environmental factors to accumulate and influence the expression of the genetic disorder. In contrast, children may not have been exposed to the environmental triggers long enough for the disorder to manifest.

Question 3

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?&#10;A)The trait is recessive.&#10;B)Mutation repair is incompletely penetrant.&#10;C)Nongenetic factors can influence expression.&#10;D)Homologous genes can undergo chromatid exchanges.

Accepted Answer

The fact that type 2 diabetes mellitus affects only one twin 70% of the time and affects both twins 30% of the time suggests that nongenetic factors can influence expression. This may include lifestyle factors such as diet and physical activity, as well as environmental factors. This is supported by numerous studies that have shown that lifestyle modifications can prevent or delay the onset of type 2 diabetes even in individuals who are genetically predisposed to the disease.

Question 4

Which statement regarding autoimmune diseases is true?&#10;A)Autoimmune disorders and diseases are more common among females than among males.&#10;B)Autoimmune disorders and diseases are more common among males than among females.&#10;C)The main characteristics of an autoimmune disorder are a reduced inflammatory response and increased susceptibility to infection.&#10;D)The main characteristics of an autoimmune disorder are a reduced inflammatory response and increased resistance to infection.

Accepted Answer

Autoimmune disorders and diseases are more commonly observed in females than in males. This discrepancy in incidence rates is thought to be related to hormonal and genetic factors. Studies have consistently shown that autoimmune diseases occur 2-10 times more often in women than men.

Option C and D are incorrect as autoimmune disorders are associated with an increased inflammatory response, which can lead to tissue damage and organ dysfunction. There is no evidence to support the assertion that autoimmune disorders reduce the inflammatory response or increase resistance to infection.

Question 5

Which statement best explains the &#34;thrifty genotype&#34; for the high incidence of type 2 diabetes?&#10;A)The person with a thrifty genotype has an efficient metabolism that generates more energy from less food and is more likely to survive famine.&#10;B)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.&#10;C)The person with a thrifty genotype stores energy rather than expends energy so that more energy is available for survival when food is scarce.&#10;D)The person with a thrifty genotype feels satiety with smaller amounts of food and is less likely to become obese,thus increasing longevity.

Accepted Answer

During historical times when populations experienced periods of plenty followed by times of famine, those people who were better at storing fat survived to pass on their genes to their offspring. People who were not metabolically "thrifty" would be less able to store fat, and they would not survive during times when there was little food.

Question 6

If a man with hereditary hemochromatosis has children with a woman who is a carrier for the disorder,what is the expected risk pattern?&#10;A)All sons will be affected;all daughters will be carriers.&#10;B)Daughters have a 50% risk for being affected;all sons will either be affected or carriers.&#10;C)Each child of either gender has a 50% risk of being a carrier and a 50% risk of having the disease.&#10;D)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.

Accepted Answer

The disease is expressed in an autosomal-recessive pattern of inheritance, and the individual must be homozygous to express the disease. Although males express the disorder at earlier ages than females, both genders are equally expressed. Because the man is homozygous for the mutation, and the woman is heterozygous, any children he fathers have a 4 out of 4 chance (100% risk) to inherit a mutated allele from him. Each child has a 2 out of 4 chance (50% risk) to inherit a mutated allele from the carrier woman. There is no chance for children of this couple to not inherit at least one mutated allele.

Question 7

Why do the clinical signs and symptoms of hereditary hemochromatosis not appear until middle adulthood?&#10;A)The adult over 50 has had more exposures to environmental insults over time.&#10;B)Prolonged dietary exposure to toxins produces clinical symptoms.&#10;C)Hereditary hemochromatosis has age-related penetrance.&#10;D)Stored iron builds up over time causing organ damage.

Accepted Answer

The cause of organ damage and symptoms in hereditary hemochromatosis is the buildup of stored iron over time. This is a single-gene disorder, and environmental factors such as diet and environmental insults do not play a significant role. Hereditary hemochromatosis does not have age-related penetrance.

Question 8

Why are women usually older than men before symptoms of hereditary hemochromatosis manifest?&#10;A)Women have a counterbalancing normal gene on their second X chromosome.&#10;B)Women lose some iron with normal menstruation during childbearing years.&#10;C)Men have a larger muscle mass and more iron-storing capability than women.&#10;D)Men have greater expression of the gene for hemoglobin than do women.

Accepted Answer

Women with hereditary hemochromatosis do not show signs of iron overload until a later age than men, often not until well after menopause, because the menstrual cycle provides natural and regular blood iron loss every month. The gene for hereditary hemochromatosis is on an autosome, not on the X chromosome.

Question 9

Why is predictive testing for Huntington disease avoided for a 4-year-old child who has one grandparent with the disorder?&#10;A)Unless one of the parents is positive for the gene mutation,a negative finding would be noninformative.&#10;B)The Huntington disease mutation is poorly penetrant and may never be expressed even when inherited.&#10;C)A 4-year-old child cannot understand or participate in the genetic counseling process.&#10;D)There are no effective primary or secondary prevention strategies for this disorder.

Accepted Answer

The Huntington disease mutation has a high penetrance, which means that a person who inherits the mutation will eventually express the disease. It also means that if a person is negative for this mutation, he or she will never develop this disease. At the present time, there is no way to prevent the disorder in a person who has the mutation. Identifying the child at this age as having the mutation provides no benefit. Although it is true that a child of this age could not understand or participate in the genetic counseling, if treatment was possible, it would be worth performing the test anyway.

Question 10

Which genetic disorder is associated with an increased risk for type 2 diabetes?&#10;A)Achondroplasia&#10;B)Down syndrome&#10;C)Huntington disease&#10;D)Hereditary hemochromatosis

Accepted Answer

Genetic syndromes or disorders that include an increased risk of diabetes mellitus (DM) are Down syndrome, Turner syndrome, and Klinefelter syndrome. The risk for DM among the other three genetic disorders listed is not greater than that for the general population.

Question 11

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 alpha1-antitrypsin (AAT)gene alleles.His wife has been tested and does not have a mutation of her AAT gene alleles.The man is worried that his three children may eventually develop COPD.What is your best response?

A)"Because your wife does not have the mutation and neither of your parents have the disease,your children will not be affected."
B)"Because your wife is not affected nor is a carrier,your children will have normal levels of AAT and their risk is the same as for the general population."
C)"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."
D)"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."

Accepted Answer

The answer of A 31-year-old man has been diagnosed with...

Question 12

Which factor is consistent with Multifactorial (Complex)Genetic Disease?&#10;A)Expression of the trait often involves mutations in several genes.&#10;B)Monozygotic (identical)twin concordance is 100%.&#10;C)Genotype consistently predicts phenotype.&#10;D)It tends to be autosomal dominant.

Accepted Answer

The answer of Which factor is consistent with Multifactorial (Complex)Genetic...

Question 13

What do each of the genes involved in Maturity-Onset Diabetes of the Young (MODY)have in common?&#10;A)They are all located on the long arm of chromosome 6.&#10;B)They each play a role in metabolism of glucose,or insulin action and release.&#10;C)Although they are of different sizes,they all contain the same exon and intron sequences.&#10;D)The genes that cause MODY are expressed only in the young and suppressed during adulthood.

Accepted Answer

The answer of What do each of the genes involved...

Question 14

An obese patient (Body Mass Index of 35)states &#34;There is no point in changing how I eat because it is all genetics anyway.&#34; What is the best response?&#10;A)&#34;Even with a large genetic component,obesity can be reduced by sensible diet and exercise.&#34;&#10;B)&#34;Let's gather some more family history about body height,weight,and eating patterns.&#34;&#10;C)&#34;You are right,you can't change your genes.There is no point in dieting.&#34;&#10;D)&#34;With your genetics,your best bet would be a low-carb Atkins-type diet.&#34;

Accepted Answer

The answer of An obese patient (Body Mass Index of...

Deck 10: Common Adult-Onset Genetic Disorders