Estimating Risk of Inherited Genetic Disease Flashcards
fitness
relative ability of organisms to survive (long enough) to pass on their genes
effect of different allels on fitness
- Not at all (neutral)
- Sometimes decrease (deleterious)
- Rarely increase (advantageous)
what may change the importance of certain allales or cause some to become more common in population
selective pressure —> favours those with a selective advantage
effect of mutation in recessive genes
rarely affects carriers
notable common recessive diseases
- sickle cell disease
- thalassaemia
what is uncommon as a cause of disease
De novo recessive mutation
what can mutation in dominant and X-linked genes be from
inherited or de novo
where are de novo mutation common in
dominant disorders (especially where disease reduces reproductive fitness)
what is up to 1/3 due to de novo mutation
lethal X-linked cases
Hardy-Weinberg equations
p + q = 1.0
1.0 = p2 + 2pq +q2 (AA:Aa:aa)
ratio of p to q always works out the same
Briefly descripe genotype and allele frequencies of offspring
- relative frequencies remain constant
- Dominant conditions (alleles) do not become more common at the expense of recessive ones
hardy-weinberg equilibrium
- allele frequencies remain constant generation to generation
- Relative proportion of genotype frequencies remain constant from generation to generation
assumptions made in hardy weinberg equilibrium
6
Only works in an ideal population:
* no mutation (it is ignored)
* not gene flow/migration
* random mating
* no selective pressure
* lare population size
* allele frequencies are equal in all sexes
what does mutation do
increase the proportion of new alleles
what does introduction of new alleles as a result of migration or intermarriage lead to
new gene frequency in hybrid population
