Polygenic Disorders and Genes In Populations

Question 1

What is a polygenic disorder?

Answer 1

Condition controlled by multiple genes

Question 2

What is an acquired polygenic disease?

Answer 2

A disease that you’re more likely to get if a family member has it, that probably has a genetic basis but is not caused by a single gene

Question 3

Which is more common, polygenic or single gene mutation genes?

Answer 3

Polygenic

Question 4

What effects do each gene in a polygenic disorder have? How then can the distribution of a phenotype parameter be displayed then?

Answer 4

Additive/cumulative

Normal distribution

Question 5

How does being a sibling of a person affected by a polygenic disease affect the sibling’s liability to getting the same disease?

Answer 5

Increases their liability - as they are more likely to have the same susceptibility genes

Question 6

What does recurrence risk mean? What does an increase in affected family members do to the recurrence risk?

Answer 6

Risk that a disease will occur elsewhere in a pedigree given that at least one member of the pedigree exhibits the disease

More family members affected = increased RR

Question 7

What does homozygosity mean?

Answer 7

Degree of genetic similarity

Question 8

What kind of genetic diseases are cleft lip and spina bifida?

Answer 8

Polygenic disorders

Question 9

How to reduce the risk of developing spina bifida?

Answer 9

Taking folic acid during pregnancy

Question 10

What does heritability mean?

Answer 10

Estimates the proportion of the total phenotypic variance of a condition that can be ascribed to additive genetic rather than environmental variance

Question 11

Which type of twin has a higher genetic concordance rate?

Answer 11

monozygotic > dizygotic

Question 12

How do you identify genes that cause multifactorial disorders: Genome-wide Association studies or Whole Genome sequencing? Why?

Answer 12

Genome-Wide Association studies

Whole genome sequencing for single gene mutations

Question 13

What is the Hardy-Weinberg distribution?

Answer 13

Explains why a genetic disorder can be more common in one population than another

Question 14

In the H-W equation for a gene pool of 2 alleles, what is the expression for the chance you are homozygous dominant, homozygous recessive and heterozygous?

Answer 14

p^2 = AA
q^2 = aa
2pq = Aa

Question 15

What does p + q =

Answer 15

1

Question 16

What does p^2 + q^2 + 2pq=

Answer 16

1

Question 17

What is an ideal H-W population?

Answer 17

Large 
Random mating
No new mutations
No selection for or against any genotype
No migration/gene flow

Question 18

What is genetic drift? THINK OF ROSS THE BARMAN (HOT AND CARRIER OF RARE GENETIC MUTATION)

Answer 18

The increased circulation of a certain allele in an isolated population such that children of members of that population are more likely to have that allele than other populations

Question 19

What is the founder effect?

Answer 19

Lower genetic diversity of founding populations that get isolated from the rest of a large population

Question 20

What is a polymorphism?

Answer 20

Coexistence of multiple alleles at the same gene locus

Question 21

What factors affect ethnic genetic differences?

Answer 21

Open/closed populations
Survival advantages
Consanguinity etc.

Question 22

Examples of ethnic differences?

Answer 22

Mediterranean/Africa = B-thalassaemia and sickle cell

Maori = chrohns

Finland = familial CJD

Amish = Maple Syrup urine disease and MCAD

Ashkenazi Jews = Tay-Sachs, Riley-Day, Familial breast cancer

Question 23

Why does consanguinity increase the risk of recessive inheritance?

Answer 23

Related partners are more likely to have mutations in the same genes