Lecture 20 - Quantitative traits, inheritance, and bayesian shit

Question 1

Are most diseases Mendelian in nature?

Answer 1

No, most have multifactorial inheritances

Question 2

What are the Mode of Inheritance of Multifactorial traits?

Answer 2

Familial clustering but without obvious family pattern

The recurrence risk is higher the more family members that are affected

Question 3

Describe a Normal Distribution curve is regard to frequency of alleles

Answer 3

Many people a relatively “normal” # of harmful alleles

Few have no harmful, all protective

Few have all harmful (have disease)

Question 4

What is a classic example of a quantitative trait?

Answer 4

Height! Large number of alleles that affect height

But environment is also incredibly important

Question 5

Describe the “threshold model”

Answer 5

Ex. More than 9 predisposing alleles is enough to cross threshold to disease

Individuals w/ less than 9 predisposing alleles are (usually) not affected

Environmental factors muddy this up

Question 6

Average risk for normal parents of one affected child having another?

Answer 6

5%

Question 7

The more children with a multifactorial disorder, _________ the recurrence risk…

Answer 7

The greater!

Question 8

Is it possible to have multi-factorial diseases affect different sexes with different frequencies?

Answer 8

Yes! In these disorders, the most likely individual to be affected is the most susceptible sex offspring of the least susceptible sex parent

Thershold may be different in different sexes

Question 9

Heritability

Answer 9

Proportion of the phenotypic variance caused by additive genetic variance

Reflected by the degree of resemblance between relatives

Estimate of the degree to which relatives will resemble one another

Identical twin studies useful here

Question 10

Bayesian theorem

Answer 10

Used to determine mutlifactorial inheritance

Combines varying factors (prior, conditional, joint, posterior) to determine % of being a carrier