Lecture 4&5 Flashcards
Polymorphism
A change in the DNA sequence, occurring naturally in populations.
Mutation
A change in the DNA sequence occuring in less than 1% of the population.
Pleiotropy
One gene affecting several independent phenotypes.
Epistasis
The masking / modulation of alleles of one gene by the alleles of another gene through an interactive (non-additive) enhancing or suppressing effect on the phenotype.
Silent / Synonymous mutation
Base changes that cause no change in the amino acid (e.g. codons AAA and AAG both encode Lysine).
Missense / Non-synonymous mutation
Base changes that cause a change in the amino acid.
Nonsense / Null mutation
Base changes that result in non-transcription into RNA, leading to the production of a non-functional protein or no protein at all (through the formation of a premature stop codon).
Lethal mutation
A mutation leading to a phenotype incapable of effective reproduction / resulting in the death of the organism.
Hypomorphic mutation
A type of mutation in which the altered gene product possesses a reduced level of activity (expression at a lower level).
Hypermorphic mutation
A type of mutation in which the altered gene product possesses a heightened level of activity (expression at a higher level).
Gene-Environment Correlation (GEC)
When the genotype and environment work in an additive / cumulative way to influence the phenotype.
Gene-Environment Interaction (GEI)
When the specific genotype is dependent upon a specific environmental influence to manifest the phenotype.
Penetrance
The proportion of the individuals in a population with a given genotype that display the phenotype associated with that genotype.
Expressivity
Variation in the expression of a phenotype among individuals of the same genotype.
Heritability
The proportion of phenotypic variation that is explained by genetic variation.
Broad sense heritability
The extent to which variation in phenotypes in a population is due to variation in genotypic values.
Narrow sense heritability
The portion of additive genetic variance that contributes to the total phenotypic variation and represents the extent to which variation in phenotypes is determined by variation in effects of alleles transmitted by parents to offspring.
