genetic diseases sl12008

Lethal recessive disorder

Genetic condition killing homozygotes before age 5.

Rare genetic disorder

Affects fewer than 1 in 2000 individuals.

Fitness (AA)

Homozygous dominant genotype fitness value of 1.

Fitness (Aa)

Heterozygous genotype fitness value of 1-hs.

Fitness (aa)

Homozygous recessive genotype fitness value of 1-s.

Mean fitness (w)

Average fitness across all genotypes in a population.

Equilibrium

State where allele frequencies remain unchanged.

Stable equilibrium

System returns to original state after perturbation.

Unstable equilibrium

System cannot return to original state after perturbation.

Mutation-selection equilibrium

Balance between mutation introducing alleles and selection removing them.

Polymorphism

Presence of multiple genetic types within a population.

Mutation rate (μ)

Frequency at which allele A mutates to allele a.

Equilibrium frequency (q*)

Frequency at which mutation-selection equilibrium is achieved.

Local stability analysis

Examination of system stability upon low frequency mutation.

Allele frequency (p)

Proportion of a specific allele in a population.

Allele frequency (q)

Proportion of the alternative allele in a population.

Next generation frequency (p')

Allele frequency in the subsequent generation.

Heterozygote advantage

Condition where heterozygotes have higher fitness than homozygotes.

Fitness component (1-hs)

Reduction in fitness due to heterozygote disadvantage.

Fitness component (1-s)

Reduction in fitness due to homozygous recessive disadvantage.

Frequency-dependent selection

Fitness of a genotype depends on its frequency.

Allele invasion

Ability of an allele to increase in frequency in a population.

Deleterious mutants

Mutations causing harm, often recessive.

Mutation selection equilibrium

Population balance between mutation and selection.

Load

Difference in fitness due to deleterious mutations.

Semidominance

Heterozygote fitness is intermediate between homozygotes.

Mutation rate (μ)

Frequency of mutations occurring in a population.

Selection coefficient (s)

Measure of fitness disadvantage due to mutations.

Heterozygous condition

Genotype with two different alleles at a locus.

Recessive mutations

Mutations expressed only in homozygous condition.

Segregational load

Fitness loss due to mating of less fit homozygotes.

Recombinational load

Fitness reduction from gene interactions during recombination.

Fitness (w)

Relative reproductive success of a genotype.

Fitness maximum (wmax)

Theoretical highest fitness achievable by a genotype.

Load calculation formula

L=hs 2pq + s q² for mutational load.

Completely recessive case

When h=0, load simplifies to μ.

Independent load factors

Load depends on mutation rate, not selection strength.

Disease-causing mutations

Mutations leading to health issues in individuals.

Long genes

Genes with higher mutation rates due to size.

Median size of disease genes

Average length of disease-related genes is 1689bp.

Example disease genes

DMD, BRCA1, and BRCA2 are long genes.

Harmful mutation comparison

s=0.1 and s=1 have equal effects if μ is same.

Fitness reduction

Population fitness decreases due to accumulated mutations.

Mutation Rate

Frequency of mutations per base pair per generation.

Recessive Lethal

Genetic condition lethal in homozygous recessive individuals.

Dominant Lethal

Genetic condition lethal in homozygous dominant individuals.

Overdominance

Heterozygotes exhibit higher fitness than homozygotes.

Heterozygote Advantage

Heterozygotes have a survival benefit in certain conditions.

Sickle Cell Anaemia

Condition caused by HbS variant of hemoglobin.

HbS

Variant of hemoglobin associated with sickle cell disease.

HbA

Wild type hemoglobin variant, normal function.

Homozygotes

Individuals with two identical alleles for a trait.

Fitness

Reproductive success of a genotype in a population.

Allele Frequency

Proportion of a specific allele in a population.

Mutation-Selection Equilibrium

Balance between mutation introduction and selection removal.

Mendelian Inheritance

Inheritance patterns based on Gregor Mendel's laws.

Stable Equilibrium

Condition where allele frequencies remain constant over time.

Random Mating

Mating without regard to genotype or phenotype.

Genetic Load

Burden of deleterious alleles in a population.

Geographical Distribution

Spread of genetic traits across different regions.

Sickle Cell Gene

Gene variant providing malaria resistance in heterozygotes.

Internal Equilibrium

State where allele frequency changes are balanced.

Allele Fixation

When an allele reaches a frequency of 100%.

Long Genes

Genes associated with higher disease prevalence.

Chromosomal Context

Influence of gene location on evolutionary dynamics.