GENETIC INTERACTIONS Flashcards
What are modifiers in genetic interactions?
Mutations that modify the expression of a different gene.
For example, the dilute locus for coat color in cats results in two phenotypes: full color or dilute color for each genotype at other loci.
What are suppressors in genetic interactions?
Suppressors are mutations that reverse the effect of another mutation, restoring the wild-type (WT) phenotype.
There are only two phenotypes: WT or mutant.
Suppression can occur within the same gene or in a different gene and can be dominant or recessive in action.
intrageneic - same gene
extragenic - different gene
What are non-allelic interactions?
These are interactions between different genes, often observed in genes that are part of the same genetic pathway.
Define epistasis.
Epistasis is when the expression of one gene is masked by the expression of one or more other genes, observed on a phenotypic level.
For example, the epistatic gene B masks the expression of gene A (hypostatic).
What is recessive epistasis?
A type of epistasis where the recessive phenotype of one gene overrides the phenotypes of another gene.
Example: If a flower is homozygous recessive (w/w), it remains white, overriding the expression of the gene that would normally convert white to pink.
What is the difference between allelic and non-allelic interactions?
Allelic interactions occur between alleles at the same locus (between homologous chromosomes).
Non-allelic interactions occur between alleles of different genes.
What is complete dominance in heterozygotes?
In heterozygotes, if complete dominance is present, the individual is phenotypically identical to a homozygous dominant.
It often relates to protein dosage, where one allele produces enough protein for a normal phenotype.
What is haplosufficiency?
A situation where a single functional gene copy is sufficient to produce enough protein for normal function, so the mutation in the recessive allele does not manifest unless both gene copies are mutated.
Yy and YY - phenotype the same
What is haploinsufficiency?
Haploinsufficiency occurs when one functional copy of a gene is not enough to produce sufficient protein, so a single mutated allele (dominant) results in a mutant phenotype.
yy and Yy - phenotype the same
How does recessive epistasis work in terms of enzymes?
The mutant phenotype of an upstream gene takes precedence. For example, if a flower is homozygous recessive for a gene that produces an enzyme (w/w), it remains white because the enzyme necessary to convert white to pink is not produced.
What is dominant epistasis?
In dominant epistasis, the dominant allele of an upstream gene inhibits the progression of a pathway.
Example: W is epistatic over G, meaning color will only be observed when the individual is homozygous recessive for W (w/w).
What is a dominant negative mutation?
A dominant negative mutation occurs when a loss-of-function allele dominates over a functional allele, compromising the activity of the wild-type protein that is co-expressed.
What are lethal alleles in genetic interactions?
Lethal alleles compromise the function of essential genes. When two lethal alleles combine in a homozygous individual, it leads to the organism’s death. Lethality can vary based on environmental factors.
What is duplicate gene action?
Two genes encode for the same biological function, creating genetic redundancy.
One dominant allele from either gene is sufficient for normal activity, and only if both genes are homozygous recessive will there be a mutant phenotype.
This is also called duplicate dominant epistasis.
What is complementary gene action
Complementary gene action (duplicate recessive epistasis) occurs when the phenotype is determined by the combined action of two genes in the same biochemical pathway.
Loss of function of either gene produces the same phenotype, and when either gene is homozygous recessive, it masks the effect of the other.
