21. Multifactorial Inheritance

Question 1

Describe the threshold model for multifactorial inheritance.

Answer 1

Polygenic traits often present with a bell curve of phenotypes. When dealing with disease, only individuals at one end of the curve develop the disease and usually they have to reach a “threshold” level of mutations before this happens.

Question 2

Example presented in lecture of how a liability threshold differs between the gender of the patient.

Answer 2

Pyloric stenosis. Higher liability for males than for females.

Question 3

Name 3 things that increase the recurrence risk of a patient developing a disease.

Answer 3

1. Higher if there is more than 1 affected family member.
2. Higher if proband is more severely affected
3. Higher if the proband is a less affected sex.

Question 4

Mutations in different genes give the same phenotype.

Answer 4

Locus Heterogeneity

Question 5

Used in twin studies to determine possibility of developing qualitative traits.

Answer 5

Concordance Rate (ex. schizophrenia)

Question 6

Used in twin studies to determine possibility of developing quantitative traits.

Answer 6

Intraclass Correlation (ex. weight)

Question 7

Describe the values obtained when calculating a measured heritability of a trait.

Answer 7

Numbers range usually from 0-1. Can be greater than 1. Closer to 1 means the trait is more genetically inherited. Closer to 0 means the trait is more environmentally acquired.

Question 8

Regions of a genome that correlate with a trait and are found by analyzing VNTRs or SNPs in a genome scan.

Answer 8

Quantitative Trait Loci (QTLs)

Question 9

Name 3 common multifactorial disorders that were discussed in lecture.

Answer 9

1. Hypertension
2. Heart Disease
3. Diabetes

Question 10

There are many environmental factors that can increase the risk of heart disease. What is one major genetic factor that can increase the risk?

Answer 10

Familial Hypercholesterolemia

Question 11

Defective protein in patients with familial hypercholesterolemia.

Answer 11

LDL receptor

Question 12

Name 3 possible therapies for treating Familial Hypercholesterolemia

Answer 12

1. Decrease fat and cholesterol intake
2. Take bile-acid binding resins
3. Statins

Question 13

Name 4 things that can increase the risk of stroke.

Answer 13

1. MELAS
2. Mutations in NOTCH3 gene
3. Protein C and S mutation (anti-clot genes)
4. Increase Factor V (clotting factor)

Question 14

Hypertension caused by a defective epithelial sodium channel (ENaC).

Answer 14

Liddle Syndrome

Question 15

Hypertension caused by increased renal salt reabsorption (WNK2 or WNK4 kinases).

Answer 15

Gordon Syndrome

Question 16

Gene associated with increased riskof developing Type 1 diabetes mellitus.

Answer 16

HLA

Question 17

Concordance rate of Type II diabetes in monozygotic twins.

Answer 17

90%

Question 18

2 genetic mutations indicated with increased risk of diabetes Type II.

Answer 18

1. Calpain - 10

2. PPAR - gamma transcription factor

Question 19

Mutation in glucokinase resulting in diabetes-like symptoms.

Answer 19

MODY

Question 20

Two genes that deal with apetite suppression that may be mutated in patients suffering from obesity.

Answer 20

1. Neuropeptide Y

2. MCR4