Genetic Basis of Multifactorial Disease

Question 1

Single gene disorders are known as

Answer 1

deterministic

Question 2

complex traits

Answer 2

probabilistic-evenifhaveall susceptibility alleles, disease still depends on whether encounter certain environmental hazards

Question 3

continuum of genetic risk

Answer 3

somepeoplewillhave only a couple of susceptibility alleles that increase risk, others will have all

Question 4

Liability threshold model

Answer 4

all factors which influence the development of a multifactorial trait or disorder can e considered as a single entity: liability
these come from a CONTINUOUS variable

Question 5

Threshold Model

Answer 5

• Discontinuous phenotype with underlying continuous distribution
• threshold exists above which the abnormal phenotype is expressed

Question 6

Population incidence

Answer 6

the proportion beyond the threshold in the general population

Question 7

familial incidence

Answer 7

Among relatives, the proportion beyond the threshold

Question 8

Heritability

Answer 8

the proportion of the total variance that is genetic.

The overall variance of the phenotype is the sum of the environmental and genetic variance.

Question 9

Mutation

Answer 9

A gene change that causes a genetic disorder (a disease causing mutation)

Question 10

a. Synonymous polymorphism

Answer 10

changes DNA sequence but not the amino acid or subsequent protein produced

Question 11

b. Non-synonymous missense polymorphism

Answer 11

changes DNA sequence and the amino acid and protein produced.

Question 12

Non-synonymous nonsense polymorphism

Answer 12

changes DNA sequence to code a premature stop codon.

Question 13

Polymorphism

Answer 13

Any variation in the human genome that has a population frequency of greater than 1%

• Any variation in the human genome that does not cause a disease in its own right. It may however, predispose to a common disease. ie is a risk factor

Question 14

Family Studies

Answer 14

This method does not take into account a risk caused by a shared environment such as a familial predilection for hamburgers in siblings

Question 15

Effect of relatives of effect in the liability curve

Answer 15

shifts to the right so familial incidence is higher than the general population incidence

Question 16

Twin Studies

Answer 16

This doesn􏰀t take into account the possibility that being a monozygotic twin itself predisposes to disease.

Question 17

Predicting risk of heart disease

Answer 17

– Cholesterol
– Blood pressure 
– Diabetes
– Smoking
treatment based on clinical parameters