Multifactorial Inheritance Flashcards
1
Q
multifactorial trait
examples
A
- results from the combined influences of multiple genes AND environmental factors
- height, weight, intelligence
2
Q
polygenic traits
A
-results from the combined influence of multiple genes
3
Q
quantitative traits
- definition
- classification
- distribution
A
- a type of multifactorial trait
- caused by the ADDITIVE effect of many genes as well as the environment
- can be represented on a number scale
- bell shape curve for the population
- height, weight, blood pressure
4
Q
threshold traits
- definition
- classification
- liability
- distribution
- examples
A
- trait is either present or absent, no middle ground
- multofactorial
- follows a bell shape curve with respect to liability
- people who surpass the threshold of liability, express the trait
- club foot, diabetes, cleft lip
5
Q
signs of multifactorial inheritance
A
- familial concentration wihtout a set pattern of inheritance
- absence of clear biochemical defect resulting from a singe gene
- considerable variation in severity and expression of the phenotype
- gender differences in the frequency of occurrence
6
Q
recurrence risk
- basis in multifacorial traits
- gender bias
- rate of multi fact vs single gene
- birth defects
A
- in multifactorial traits, based on population and family studies and are called empiric risks
- often different for males and females
- multifactorial typicaly have a lower rate than single gene
- birht defects are typoically 4% but can vary
7
Q
rules for common birth defects
- multiple family members
- severity of disease
- gender bias
- remote family members
- risk equation for first degree relatives
A
- reccurence risk is higher if more than one family member is affected
- the greater the severity of the disease in the pro band, the greater the recurrence risk
- recurrence is great if the proband is of a less commonly affected sex
- recurrence risk decreases drastically if more remote family members are affected
- recurrence risk for first degree relatives is approx the square root of the population incidence
8
Q
heritability
- what
- how it is derived
A
- identifies the genetic distribution of the disorder
- comes from observations of familial aggregation patterns
9
Q
family aggregation patterns associated with heritability
- monozygotic vs dizygotic twins
- adopted children
A
- more common in biological relatives than in nonbiological
- monozygotic twins for frequently concordant than dizygotic twins
- monozygotic twins reared separately have greater concordance than expected by chance
- adopted children more closely take after their biological parents than adopted despite living in the same environment
10
Q
inheritance of coronary artery disease
risk is higher if
A
- positive family history (one or more first degree family members) is a sig risk factor along with envirmental quess (smoking, obesity, hypertension, etc.)
- this raises risk by 2-7 fold
- risk is higher if: more than one effected am member, if the relative is the least likely of the two genders, if the fan age of onset is under 55
- over 15 genes involved in lipid metabolism
11
Q
positive family history
A
-one or more of first degree family members are affected
12
Q
breast cancer
A
- increases with pos family history, even without the BRCA gene mutation
- womens risk doubles if first degree fan affected
- increases with more relatives or earlier age of onset
- environmental: nulliparity, first child after 30, high fat diet, alcohol, estrogen replacement therapy
13
Q
Alzheimers
A
- doubles in indies who have a first degree family member
- apolipoprotein E is a risk factor and has three major alleles: E2,3,4
- E4 has the strongest association (homozygotes much more prone)
- there are still many people without this gene defect that develop alzheimers
- whites and japanese have a higher risk
