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Flashcards in Multifactorial Inheritance Deck (13):
1

multifactorial inheritance definition

- combined contribution of genes and environmental factors in the causation of a particular disease or trait

2

trait

distinct variant of a phenotypic characteristic that may be inherited

3

single gene trait

results from the influence of only one gene

4

multifactorial trait

results from the combined influence of multiple genes and environmental factors

5

signs of multifactorial inheritance

- no clear mendelian inheritance
- absence of clear defects from a single abnormal gene
- VARIATION in severity and expression of phenotype
- gender differences in frequency of occurrence

6

quantitative traits

- think number (continuous range of measurement)
- follows a normal distribution curve
- e.g. height, weight

7

threshold traits

- think presence or absence of trait
- bell-shaped distribution of liability
- once ind. exceeds the threshold of liability

8

liability

total combined genetic and environmental factors that influence the development of a multifactorial disorder or trait
- once past the threshold, you're affected
- liability cannot be measured (determined from the incidence of the disease in a group)

9

liability sex differences
- cleft lip and palate
- congenital hip dysplasia
- pyloric stenosis

- cleft lip/palate M > F
- congenital hip dysplasia
F > M
- pyloric stenosis M > F
digestive problems

10

recurrence risk rules for multifactorial inheritance

- proband more severe, greater risk
- more than one fam member, greater risk
- distantly related, risk decreases
- proband is of less commonly affected sex, greater risk
- risk for 1st degree relatives is approx sq. rt. of population incidence of trait
- in GENERAL, recurrence risk is approx 4%, but if defect is part of underlying syndrome, could be much higher

11

heritability

measure of proportion of total phenotypic variance of a trait that is caused by a gene
- always between 0 and 1

12

twin studies

- heritability of a trait estimated for concordance rates for monozygotic twins and dizygotictwins
- if MZ share a trait more often than DZ, then more genetic

13

Linkage analysis

- determine whether inheritance of a marker predisposes to a certain trati/disease in family
- identifies a region of genome where candidate disease allele could be found