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.
