Multi-Factorial Inheritance- Lecture 9/2/21

Question 1

Trait

Answer 1

Distinct variant of a phenotypic characteristic that may be inherited

Question 2

Monogenic trait

Answer 2

Results from the influence of only one gene (Mendelian)

Question 3

Polygenic trait

Answer 3

Results from the combined influence of multiple genes

Question 4

Multi factorial trait

Answer 4

Results from the combined influence of multiple genes and environmental factors

Question 5

Quantitative trait

Answer 5

Continuous range of measurement, numerical scale, follows a normal or bell shaped distribution in populations

Question 6

Threshold traits

Answer 6

Trait is either present or absent, liability follows a bell shaped distribution, those individuals exceeding the threshold on the liability scale will express trait

Question 7

Liability

Answer 7

Total genic and environmental factors that contribute to the development of a trait

Question 8

Signs of multi factorial inheritance

Answer 8

1. Familial concentration of a disease or trait without clear Mendelian pattern
2. Absence of clear biochemical defects resulting from a single abnormal gene
3. Considerable variation in severity and expression of the phenotype
4. Differences in the frequency of occurrence based on sex

Question 9

Recurrence

Answer 9

The chance that trait recurs in a member that is not the proband, often not exact but obtained by observation of family and population studies

Question 10

Recurrence risk rules

Answer 10

1. Greater the severity of the proband, the greater the recurrence risk
2. If the proband is the less commonly affected sex
3. Decreases rapidly in more distantly related individuals
4. Higher if more than one family member affected
5. Risk for first degree relatives is approx the square root of the population incidence

Question 11

Heritability

Answer 11

The proportion of the total phenotypic variance of a trait in a population that is due to genetics

Question 12

How to use twin studies to quantify multi factorial traits

Answer 12

<100% concordance in monozygotic twins suggests an environmental component
Monozygotic concordance>dizygotic concordance suggests genetic component

Question 13

Heritability number

Answer 13

The closer it is to one, the closer the trait is to being genetically controlled as compared to environmental

Question 14

Linkage analysis

Answer 14

Whether the inheritance of a genetic marker is associated with a particular disease/trait in a family

Question 15

Association studies

Answer 15

Identify specific marker alleles for particular disease/trait within an already designated region or across genome using SNPS

Question 16

Limitations of association studies

Answer 16

SNP is not necessarily causally related

A larger number of markers are needed because the marker allele needs to be closely linked to disease locus

Question 17

Heritability (equation using twin studies)

Answer 17

H2= (MZ concordance-DZ concordance)x2

Closer to one-> more genetic

Question 18

Liability greater in males (three)

Answer 18

Pyloric stenosis, autism, cleft lip/palate