Estimating Risk of Inherited Genetic Disease Flashcards
What is meant by fitness?
Relative ability of organisms to survive and pass on genes
What is an allele that increases fitness?
Advantageous allele
What is a neutral allele?
Doesn’t effect fitness
What is a deleterios allele?
A decrease in fitness
What affects the health of the population?
Frequency of alleles
Do dominant alleles become more common from generation to generation?
No, relative frequencies remain constant
genotype frequencies also remain constant
What are the assumptions underlying the HWE?
- Mutation can be ignored
- Migration is negligible (No gene flow)
- Mating is random
- No selective pressure
- Population size is large
- Allele frequencies are equal in sexes
What does the introduction of new alleles as a result of migration or intermarriage leads to?
New gene frequency in hybrid population.
What is the result of non-random mating?
Increase mutant alleles
Increasing proportion of affected homozygotes
What is assortative mating
Partners with similar phenotype or genotype mate more frequently
What is Consanguinity
Marriage between close blood relatives.
Shown by double horizontal line
What is natural selection?
Gradual process where biological traits become more or less common in population
What is Negative selection?
Reduces reproductive fitness
- decreases prevalence of traits.
- leads to gradual reduction of mutant allele
What is positive selection?
Increases reproductive fitness.
- Increases prevalence of adaptive traits.
- Heterozygote advantage
What is the effect of small population?
Can exhibit “genetic drift” and cause “founder effect”.
What is meant by genetic drift?
Random fluctuation of one allele transmitted to high proportion of offspring by chance.
What is the founder effect?
Reduction in genetic variation
Small subset of large population is used to establish new colony
What is the bottleneck effect?
Catastrophe results in a population with high expression of certain phenotype, regardless of wether or not it is advantageous to population
What is anticipation
Disease presents earlier
Increasing severity in successive generations
What is HNPCC
Autosomal dominant condition
Genetic mutation and impaired DNA MMR
Increases risk of cancers, including colon cancer
Describe Huntington’s disease
Autosomal dominant disease
50% chance passing to child
Brain stops working properly overtime
Describe sickle cell disease
Autosomal recessive disease
Affects RBC
Describe X-linked recessive mutations
Men more likely affected
Only one X chromosome - only needs one mutated allele
