Deck 16: Identifying the Roles of Genetic and Environmental Factors in Disease Causation

Question 1

In a study of Korean migrants to the United States,the following standardized mortality ratios (SMRs) were found for disease X.What is the most reasonable conclusion to be drawn from these data? Use the table below to answer the question. Standardized Mortality Ratios by Migrant History

A) Environmental factors are unimportant in the etiology of disease X.
B) The data suggest potentially important genetic components.
C) Environmental factors exposed between age 15 and 30 are associated with disease X.
D) Migrants are highly representative of the population in their native country.
E) Age at the migration is not related with disease X.

Answer 1

C
Korean migrants who left the country at age younger than 15 have relatively lower SMR compared with Korean migrants who left the country at age older than 30 and native Korean living in Korea.This indicates that environmental factors to which people are exposed at ages between 15 and 30 have an effect on disease X SMR."Environmental factors are unimportant in the etiology of disease X" is not correct.If environmental factors were not unimportant,SMR will not be changed by immigrant status."The data suggest potentially important genetic components" is not correct.If genetic components were important factors,SMR in children of Korean ancestry will be high."Migrants are highly representative of the population in their native country" is not correct.Migrants cannot be representative of the population from the country."Age at the migration is not related with disease X" is not correct.Age at migration shows a major role for SMR in this study.

Question 2

A total of 1,500 pairs of adult twins,600 monozygotic and 900 dizygotic,were studied to estimate the concordance for a childhood cancer.In the 600 monozygotic twins,40 of the pairs were concordant for the disease,60 of the pairs were discordant for the disease,and neither twin had the disease in the remaining 500 pairs.In the 900 dizygotic twins,30 of the pairs were concordant for the disease,120 of the pairs were discordant for the disease,and neither twin had the disease in the remaining 750 pairs.What is the concordant rate,in monozygotic twins,of the disease in twin pairs with at least one affected member?

A) 0.1
B) 0.4
C) 0.6
D) 0.7
E) 1.5

Answer 2

B
The concordant rate of the disease in twin pairs with at least one affected member among monozygotic twins is 40,the number of pairs with concordant,divided by 100,40 plus 60,the total number of pairs with at least one affected member.The concordant rate equals 0.4.

Question 3

Huntington disease is an autosomal dominant disease.It is characterized by the adult onset of abnormal movements,cognitive impairment,and,often,psychiatric symptoms.For its type of transmission pattern (autosomal dominant) it is considered a

A) complex genetic disease.
B) multiple gene disease.
C) environmental disease.
D) vector borne.
E) Mendelian disease.

Answer 3

E
Mendelian diseases are characterized for being mutations in single genes affecting either autosomal or sexual chromosomes,and being either dominant or recessive.Such information is enough to answer this question because the sentence indicates that Huntington is an autosomal dominant disease.

Question 4

A total of 1,500 pairs of adult twins,600 monozygotic and 900 dizygotic,were studied to estimate the concordance for a childhood cancer.In the 600 monozygotic twins,40 of the pairs were concordant for the disease,60 of the pairs were discordant for the disease,and neither twin had the disease in the remaining 500 pairs.In the 900 dizygotic twins,30 of the pairs were concordant for the disease,120 of the pairs were discordant for the disease,and neither twin had the disease in the remaining 750 pairs.What is the discordance rate,in dizygotic twins,of the disease in twin pairs with at least one affected member?

A) 0.1
B) 0.2
C) 0.6
D) 0.8
E) 1.5

Question 5

A total of 1,500 pairs of adult twins,600 monozygotic and 900 dizygotic,were studied to estimate the concordance for a childhood cancer.In the 600 monozygotic twins,40 of the pairs were concordant for the disease,60 of the pairs were discordant for the disease,and neither twin had the disease in the remaining 500 pairs.In the 900 dizygotic twins,30 of the pairs were concordant for the disease,120 of the pairs were discordant for the disease,and neither twin had the disease in the remaining 750 pairs.What is the most reasonable conclusion to be drawn from these data?

A) Genetic factors are unimportant in the etiology of childhood cancer.
B) The data suggest a potentially important genetic component.
C) The incidence of childhood cancer within monozygotic twins is higher than dizygotic twins.
D) The prevalence of childhood cancer within dizygotic twins is higher than monozygotic twins.
E) Environmental factors are the major determinants of child food cancer.

Question 6

The following suggests environmental factors causing a disease:

A) Monozygotic twins getting the same disease
B) Family history of disease
C) Early development
D) A rapid change in the trends of disease over time
E) Biologic brothers adopted by different families getting the same disease