Population Genetics

Tay-Sachs disease

A rare Autosomal Recessive disease characterized by hexosaminidase A deficiency and accumulation of GM2 gangliosides in ganglion cells.

Gaucher disease

A lysosomal storage disease characterized by glucocerebroside accumulation in macrophages, resulting in Gaucher cells.

GM2 gangliosidoses

A group of diseases caused by mutations in HEXA, HEXB, or GM2A genes, resulting in the accumulation of GM2 gangliosides in neuronal lysosomes.

Allele Frequency

The frequency of a specific allele in a population, calculated as the number of copies of the allele divided by the total number of alleles in the population.

Genotype Frequency

The frequency of a specific genotype in a population, calculated as the number of individuals with that genotype divided by the total population size.

Hardy-Weinberg law

A principle that describes the relationship between allele and genotype frequencies in a population under certain assumptions, including random mating, large population size, and constant allele frequencies.

Hardy-Weinberg equilibrium

A state in which allele and genotype frequencies in a population remain constant from generation to generation, according to the Hardy-Weinberg law.

Stratified Mating

Mating patterns in which individuals within a population preferentially mate with individuals from the same subgroup, leading to non-random distribution of alleles.

Assortative Mating

Mating patterns in which individuals choose mates based on shared traits, leading to an increase in homozygosity and mutant allele frequency.

Consanguineous Mating

Mating between individuals who are closely related, resulting in an increased likelihood of rare recessive alleles becoming homozygous.

Genetic Drift

Random fluctuations in allele frequencies in small populations due to chance events, leading to changes in the genetic composition of the population.

Founder Effect

A phenomenon in which a small group of individuals establishes a new population, leading to a different allele frequency distribution compared to the source population.

Gene Flow

The transfer of alleles between populations through migration, leading to changes in allele frequencies.

Heterozygote Advantage

A situation in which heterozygous individuals have a higher fitness compared to both homozygous genotypes, leading to the maintenance of a disease-causing allele in the population.

Selection

The process by which certain alleles or genotypes are favored or disfavored in a population, leading to changes in allele frequencies over time.

Fitness

The reproductive success of an individual or genotype, measured as the proportion of offspring that survive to reproductive age.

Mutation

A change in the DNA sequence of a gene, leading to the creation of new alleles and genetic variation in a population.

Tay-Sachs disease

- onset: 6 - 12 months

- progressive neural degeneration

- loss of motor skills, responsiveness

- seizures

- loss of movement, hearing, and vision

- cherry red spot @ fovea centralis

- death @ 2 - 5 years

cherry red spot

GM2 gangliosides accumulate in ganglion cells of retina (esp. in the macula)

- macula become milky or pale grey

- fovea has few ganglion cells and remains bright red (from underlaying vascular choroid)

- subnormal vision as ganglion cells degenerate

Gaucher disease Type 1

nonneuropathic

- bone disease

- hepatosplenomegaly

- anemia

- thrombocytopenia

Gaucher disease Type 2

acute infantile neuropathic

- onset by 3 months

- extensive brain damage

- death before 2 years

Gaucher disease Type 3

chronic neuropathic

- slower progression

- neural damage

- seizures

- decreased cognition

Gaucher disease Perinatal Lethal

Perinatal Lethal

- severe neural damage

- fluid accumulation