Estimating risk of inherited genetic disease Flashcards
(33 cards)
Fitness
Relative ability of organisms to survive and pass on genes
What does fitness depend on?
Types of alleles eg neutral, deleterious or advantageous
Do deleterious mutations sometimes or rarely decrease fitness?
Sometimes
Do advantageous mutations sometimes or rarely increase fitness
Rarely
Frequency of alleles affect healthy population
Population genetics
1 gene with 2 alleles what are p and q
p = dominant q = recessive
Genotype frequency
GG/total
Allele frequency
Gt/ total alleles ( NB double the number as alleles separate)
Do dominant conditions become more common at the expense or recessive alleles?
NO
Hardy-Weinberg principle
Use quadratics
What are constant generation to generation?
Allele frequency and relative proportion of genotype frequency
p squared = q squared = 2pq=
1
What can HWE allow?
Calculate risk in genetic counselling
Plan population based carrier screening programmes
p squared
Homozygous dominant
q squared
Homozygous recessive
pq
Heterozygous
When is HWE not always achieved?
Blood type
Name some characteristics of an ideal population
- Mutation can be ignored and migration is negligible
- Mating is random and there are no selective pressure
- Allele frequency equal in sexes in large population
Do mutations increase or decrease proportion of new alleles?
Increase
What else increases the proportion of new alleles?
Migration and intermarriage
Give an example of migration and proportion of alleles
60% of men in NW Scotland have Scandinavian DNA and leads to a hybrid population
What does non random mating do?
- Increase mutant alleles
- Increase affected homozygotes
Assorative
Shared characteristic
Consanguinity
Close blood relatives
