Multifactorial Conditions

Question 1

Polygenic

Answer 1

A disorder or trait caused by a combined small additive effects of multiple genes

Question 2

Multifactorial

Answer 2

A disorder or trait caused by a combination of genetic and environmental factors

Question 3

Characteristics

Answer 3

-phenotype is familial, but no pattern of inheritance -recurrence risk is higher when more than one relative is affected -when the phenotype is more common in one sex, the risk is higher for relatives of the proband of the less susceptible sex -consanguineous parents face an increased risk for having a child with a multifactorial condition

Question 4

Risk for first degree relatives

Answer 4

square root of the population risk second degree relatives face a significantly lower risk than 1st degree. Risk decreases rapidly for more distant relatives.

Question 5

3 categories of multifactorial inheritance

Answer 5

1. continuous variation 2. threshold traits 3. common diseases

Question 6

Continuous variation

Answer 6

Frequently follow a normal distribution (ex// height, intelligence, weight). Abnormality involving one of these traits is considered an extreme variant of the normal distribution.

Question 7

Threshold traits

Answer 7

multifactorial traits which do not follow a normal distribution. They are either present or absent and there is no sharp delineation between normal and abnormal phenotypes (ex// CHD, NTDs, cleft lip +/- cleft palate)

Question 8

Common diseases

Answer 8

Conditions that are common in the adult population and contribute to a significant proportion of morbidity and mortality in this population (ex// hypertension, diabetes, coronary heart disease, mental illness)