Non-Medelian: Multifactorial inheritance Flashcards

(10 cards)

1
Q

Multifactorial Inheritance

A

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

  • Considerable variation in severity and expression of the phenotype
  • Gender difference in the frequency of occurrence
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Multifactorial Traits

A

Quantitative Traits- measured on a numerical scale; tend to follow ‘bell-shaped’ distribution in populations (i.e. height, weight, and BP)

Threshold Traits- Either present or absent. A bell-shaped distribution in the population with respect to liability to a trait, and only those individuals exceeding the threshold on the liability scale will actually exhibit the trait (i.e. club foot, diabetes, cleft lip, and pyloric stenosis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Liability

A
  • Total combined genetic and environmental factors that influence the development of a multifactorial disorder or trait
  • Cannot be measured; determined from the incidence of the disease in a group using statistics of the normal distribution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Recurrence risk for common birth defects

A

~4%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Recurrence Risk

A

The likelihood that a trait or disorder present in one family member will occur again in other family members in the same or subsequent generations

-Multifactorial traits have a recurrence risk less than that of single gene disorders, but are not insignificant.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Recurrence Risk Rules for MF inheritance

A
  1. The greater the severity, the higher recurrence
  2. Recurrence risk is higher if more than one family member is affected
  3. Decreases rapidly in more remotely related individuals
  4. Greater if the pro band is of the less commonly affected sex
  5. For first degree relatives it is approximately the square root of the population incidence of the trait
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Heritability

A

Measure of the fraction of the total phenotypic variance of a trait in a population that is caused by genes; this value lies between 0 and 1
-Evidence of genetic contribution to a disorder comes from;
observations of familial aggregation and twin studies (comparing concordance rate of monozygotic twins vs dizygotic twins)

Heritability= (MZ concordance - DZ concordance) x 2
Concordance Rate = # of all concordant pairs/ # of all twin pairs.

i.e. when 100% genetic MZ = 1 and DZ = 0.5 so Heritability=1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Linkage Analysis

A
  • Used to determine whether the inheritance of a genetic marker predisposes to a particular disease/trait in a family
  • Goal is to find a region of the genome where a candidate disease allele could be found
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Linkage Analysis: Steps

A
  1. Determine how far apart the loci are by calculating recombination frequency
  2. Assess the strength of evidence for linkage by calculating the LOD score
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Association Studies

A

To identify specific alleles for a particular disease/trait within an already designated gene region
-Hypothesis is that a particular allele occurs more frequently in individuals with the disease than in controls

How well did you know this?
1
Not at all
2
3
4
5
Perfectly