Polygenic Disorders and Genes In Populations Flashcards
What is a polygenic disorder?
Condition controlled by multiple genes
What is an acquired polygenic disease?
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
Which is more common, polygenic or single gene mutation genes?
Polygenic
What effects do each gene in a polygenic disorder have? How then can the distribution of a phenotype parameter be displayed then?
Additive/cumulative
Normal distribution
How does being a sibling of a person affected by a polygenic disease affect the sibling’s liability to getting the same disease?
Increases their liability - as they are more likely to have the same susceptibility genes
What does recurrence risk mean? What does an increase in affected family members do to the recurrence risk?
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
What does homozygosity mean?
Degree of genetic similarity
What kind of genetic diseases are cleft lip and spina bifida?
Polygenic disorders
How to reduce the risk of developing spina bifida?
Taking folic acid during pregnancy
What does heritability mean?
Estimates the proportion of the total phenotypic variance of a condition that can be ascribed to additive genetic rather than environmental variance
Which type of twin has a higher genetic concordance rate?
monozygotic > dizygotic
How do you identify genes that cause multifactorial disorders: Genome-wide Association studies or Whole Genome sequencing? Why?
Genome-Wide Association studies
Whole genome sequencing for single gene mutations
What is the Hardy-Weinberg distribution?
Explains why a genetic disorder can be more common in one population than another
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?
p^2 = AA q^2 = aa 2pq = Aa
What does p + q =
1
What does p^2 + q^2 + 2pq=
1
What is an ideal H-W population?
Large Random mating No new mutations No selection for or against any genotype No migration/gene flow
What is genetic drift? THINK OF ROSS THE BARMAN (HOT AND CARRIER OF RARE GENETIC MUTATION)
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
What is the founder effect?
Lower genetic diversity of founding populations that get isolated from the rest of a large population
What is a polymorphism?
Coexistence of multiple alleles at the same gene locus
What factors affect ethnic genetic differences?
Open/closed populations
Survival advantages
Consanguinity etc.
Examples of ethnic differences?
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
Why does consanguinity increase the risk of recessive inheritance?
Related partners are more likely to have mutations in the same genes
