Estimating Risk Of Inherited Disease Flashcards
What is reproductive fitness?
Ability of organism to survive long enough on pass on their genes.
Recessive conditions that are common
Sickle cell disease
Thalassaemia
Recessive genetic genes that are associated with selective pressures
Malaria resistance
Plague/ cholera resistance
De novo mutations are very common in:
Dominion ant and x-linked genes/ conditions
NOT recessive
In Dominant and S. linked disorder:
De novo mutations keep these conditions alive
If there weren’t any de novo mutations, they would die out.
Up to 1/3 of lethal x linked conditions are down to de novo mutations
Genotype frequencies
Aa
AA
Aa
Hardy - Weinberg equilibrium equilibrium
Relative frequencies of the alleles … Remain constant unless something changes .
Ideal population?
Mutation can be ignored Migration is negligible Mating is random No selective pressure Population size is large Allele frequencies are equal in the sexes.
Introduction of new alleles as a result of migration or intermarriage
Leads to a new gene frequency in hybrid population.
What % of men in the UK have Norwegian DNA?
60%
Non-random mating - assortative mating
Choosing of partners due to shared characteristics
E.g deafness and sign language
Non-random mating - consanguinity
Marriage between close blood relatives
E.g cultural pressures for inter-marrigage within clans/ religions etc
Natural selection
Gradual process by which biological traits become more or less common in a population
What is glucose -6-phosphate dehydrogenase (G6PD) deficiency associated with?
Malaria
Small populations?
More likely to get genetic drift and founder effect
Genetic drift
Random fluctuation of one allele transmitted to high proportion of offspring by chance
Mutations are widespread and neutral
Chance of random events rather than natural selection
Founder effect
Reduction in genetic variation that results when a small subset of a large population is used to establish a new colony.
Bottleneck effect
Huge disaster e.g tsunami and everyone dies
Reduces genetic diversity as have to start from begnining with lack of genetic diversity.
Cystic fibrosis in Faroes
Result of founder effect
ORkney
Huge family with BRCA1 mutation.
Amish in Pennsylvania (small no of German immigrants to US
Ellis-van crenels syndrome:
Constant baby teeth
Extra fingers
Learning problems
Applications of HWE
Useful for calculating risk in genetic counselling
Useful for planning population bases carrier screening programmes
