Multifactorial Inheritance Flashcards Preview

Me: Genetics MBS > Multifactorial Inheritance > Flashcards

Flashcards in Multifactorial Inheritance Deck (13):

multifactorial inheritance definition

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



distinct variant of a phenotypic characteristic that may be inherited


single gene trait

results from the influence of only one gene


multifactorial trait

results from the combined influence of multiple genes and environmental factors


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


quantitative traits

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


threshold traits

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


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


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



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


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


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