10.11.18 Probabilities in Populations Flashcards
What are the molecular mechanisms of hemoglobinpathies?
- Novel property mutations
- Loss of function
- Heterochronic or ectopic expression
Mutation that confers a novel property on the protein without necessarily altering its normal functions (Sickle Cell Disease)
Novel property mechanism
How is SCD genetically passed on?
Autosomal recessive
Study of the distribution of alleles in populations and of how the frequency of alleles and genotypes are maintained or changed
Population genetics
What is the Hardy-Weinberg Principle (2 equations)?
p+q=1
p^2 + 2pq + q^2 =1
What is the Hardy-Weinbergy approximation for carrier frequency?
The carrier frequency is about twice the minor allele frequency which twice the square root of prevalence
2pq= 2q
What are the assumptions in Hardy Weinberg Equilibrium?
- Large population
- Random mating
- Constant allele frequency
Fluctuations in the frequency of alleles resulting from chance occurrences operating in small populations
Genetic drift
Non-random distribution of alleles among the individuals who founded particular subpopulations
Founder (bottleneck) effect
What are some examples of non-random mating?
- Stratification
- Assortative mating
- Consanguinity
Population that contains a number of subgroups that have remained genetically separate during modern times (AA and White mating)
Stratification
Choice of mate because the mate possesses some particular trait (deaf x deaf)
Assortive mating
Mating with someone who is related by descent
Consanguinity
What are some exceptions to constant allele frequency?
- Selection against or for alleles
- Mutation
- Migration
Measure of the number of offspring or affected persons who survive to reproductive age
Minor allele causing death; heterozygote advantage
Fitness
introduction of new alleles in a population
Mutation
Mutations associated with a reduction or a complete loss of one or more of the normal function of a protein (Thalassemia)
Loss of function
More than 200 pathogenic mutations in the HBB gene have been described. This is an example of what?
Allelic heterogeneity
Inappropriate expression of a gene at an abnormal time or place (Hereditary persistence of fetal Hb)
Heterochronic or ectopic gene expression
What molecular mechanism does Factor V Leiden illustrate?
Gain of function- mutant protein enhanced in normal properties and increases production of normal protein (enhanced thrombin generation – venous thrombosis; persists longer in circulation)
Loss of half of the normal activity of a protein; refers to dominant phenotypes
Haploinsufficiency
Abnormal protein causes an abnormal phenotype by interfering with function of the product of the normal allele (osteogenesis imperfecta)
Dominant negative effect
Number of different mutant alleles at a single locus
Allelic heterogeneity
Phenotype can be produced by mutations at two or more different loci
Locus heterogeneity
At least two cell lines are present that differ in genotype or karyotype
Mosaicism
Probability that a gene will have any phenotypic expression
Penetrance
One gene has multiple phenotypic effects, particularly when the effects are not obviously related
Pleiotropy
Severity of expression of the phenotype, although there is always some degree of expression present
Variable expressivity
How is Factor V Leiden inherited?
How are thalassemias, SCD inherited?
How are blood groups inherited?
Autosomal dominant
Autosomal recessive
Codominant
