Multifactorial

Question 1

difference between single gene and multifactorial gene

Answer 1

single - determined by alleles at a single locus (ex: AR, AD, X linked diseases)

multifactorial/complex - genes + environment

Question 2

amount of diseases in the human population that can be attributed to multifactorial disorders

Answer 2

a hell of a lot

Question 3

explains disorders that do not show clear Mendelian inheritance but show familial aggregation

Answer 3

multifactorial inheritance

Question 4

what does it mean for multifactorial disorder to show quantitative trait

Answer 4

number of contributing (dominant) alleles determines phenotype not the specific combination (so can be additive [AA] or non-additive [aa])

Question 5

mutations or variations in more than one gene contribute to the trait describes?

Answer 5

polygenic

Question 6

environmental factors that can influences diseases

Answer 6

diet, environmental toxins, lifestyle

Question 7

polygenic theory of quantitative traits shows what type of expression/curve

Answer 7

normal or gaussian distribution (so a range/variations in phenotypes)

Question 8

frequency if only controlled by one gene

frequency if controlled by two genes (digenic)

Answer 8

1 gene: 1, 2, 1

2 genes : 1, 4, 6, 4, 1

Question 9

what happens to phenotype if controlled by more than one gene

Answer 9

broader range of phenotype/continuous phenotype

Question 10

human characteristics controlled by polygenic/quantitative traits (does not exclude that there are environmental factors)

Answer 10

height, weight, skin color, intelligence etc

Question 11

Say intelligence is a polygenic trait (which it is) and controlled by only two genes (which it is not). Two alleles exist at each locus, one fully additive (A and B) and one non-additive (a and b). How smart are you if your mother is A/A B/B and your father is a/a B/B?

Answer 11

intermediate between mother and father

Question 12

all factors that contribute to a disease and the type of graph it produces

Answer 12

liability

normal/gaussian distribution

Question 13

point where there is enough contribution to some underlying quantitative variable to cause expression of abnormal phenotype

Answer 13

threshold

Question 14

does where you sit in a gaussian distribution a result of your genes and environment

Answer 14

yeah

Question 15

what happens to the distribution curve in families with “bad genes” and what does that mean

Answer 15

curve shifts to the right meaning more people are above the threshold

Question 16

definition: the more closely related you are to someone with a complex disease, the more likely you are to have some of the same alleles

Answer 16

familial relative risk

Question 17

what happens to your risk of getting a disease for every degree distance you are away from affected persons

Answer 17

it decreases by 1/2 with every degree

1/2 (sibs and parentals) –> 1/4 (grandparents, uncles) –> 1/8 (first cousins, great grand parents)

Question 18

equation for relative risk ratio

Answer 18

lambda = prevalence of disease in relatives of affected person / prevalence of disease in general population

Question 19

what does it mean to have a lambda of 1

Answer 19

relative is no more likely to develop the disease than any other individual in the general population so basically no genetic influence

Question 20

what does sit mean to have a large lambda or a low lambda

Answer 20

large lambda - greater familial aggregation

low lambda - less likely familial aggregation and more likely greater impact of environment and multiple genes

Question 21

is the risk of recurrence lower or higher in relatives of severely affected individuals

Answer 21

higher

Question 22

what does it mean if multiple members in the family are affected with the same multifactorial inheritance disease

Answer 22

genes contribute greatly to the disease so higher lambda and greater risk of having disease if part of this family

Question 23

pyloric stenosis is more common in what population

Answer 23

males (have a lower liability threshold)

Question 24

what happens to recurrence risk if the less likely affected sex is the one with the disease

Answer 24

then there is a greater recurrence risk of the disease …and even greater for the more susceptible sex

Question 25

what does it mean to identify the genetic component of a complex disease

Answer 25

means to identify the heritability of the disease

Question 26

supplementation of the mother’s diet with folate can reduce the incidence of neural tube defects by about 70% is evidence of what

Answer 26

evidence for environment

Question 27

a woman who has had one child with a neural tube defect such as spina bifida, has ~3% risk of having another (much higher than population risk) is evidence of what

Answer 27

evidence for genetics

Question 28

incidence of breast cancer is lowest in Asian women but after migrating to the US and after a few generation, incidence was the same as US women …what does that mean

Answer 28

strong evidence for environment although it appeared to be genetics

Question 29

are most cancers genetically or environmentally associated

Answer 29

environment

Question 30

difference between a monzygotic and a dizygotic twin

Answer 30

monozygotic - from same ovum and genetically same with exception of mitochondrial DNA

dizygotic - from two separate ova but share intrauterine environment (just sibs - 50% identical)

Question 31

what is concordance and discordance

Answer 31

concordance - twins have the same disease

discordance - one twin has disease while other does not

Question 32

what happens if concordance is 100% or <100% in MZ twins

Answer 32

concordance 100% - genetically determined

concordance <100% - environmentally determined

Question 33

the greater the discordance, the greater the…?

Answer 33

environmental input

Question 34

what does it mean if concordance is similar in both dizygotic and monozygotic twins

Answer 34

then environment plays a big role

Question 35

what do associate studies not analyze

Answer 35

they do not analyze familial inheritance patterns instead they are case control studies

Question 36

common diseases are accounted for by genetic variants found in what percent of the population

Answer 36

1-5%

Question 37

molecular diagnostic used in common disease-common variant hypothesis

Answer 37

SNP

Question 38

account for the majority of the disease load in human populations

Answer 38

multifactorial disease