Gene mapping Flashcards
Define epistasis?
Allele at one location affects the phenotypic expression of an allele at another.
Define epistatic allele?
Masks the expression.
Define hypostatis allele?
Is the masked allele.
What is dominant epistasis?
A single dominant allele at an epistatic locus is sufficient to mask the phenotype.
Produces a 12:3:1 ratio
What is recessive epistasis?
Two recessive alleles at an epistatic locus masks the phenotype of the second gene.
Produces a ratio of 9:3:4
What is duplicate dominant epistasis?
When either gene is homozygous recessive, the phenotype of the other is masked.
Both the genes are in the same pathway, both are needed to produce intermediates without which the final product can’t be synthesised.
What is double recessive epistasis gene duplication?
When either gene has a dominant allele it masks the phenotype produced by a homozygous genotype at both loci.
Both genes have the same role in the pathway (enzyme to convert precursor). One is redundant so as long as one is functional the product can me synthesised.
What are suppressors?
Allele of a gene that reverses the effect of a mutation at another locus by restoring the WT phenotype. The alleles usually have no effect in the absence of the other mutation.
What are biochemical pathways?
Epistatic genes act upstream in the pathway (before the hypostatic gene). They can be used to deduce the order of genes based on the accumulation of different products with mutation of different genes in the pathway, and the ability of ability of different chemicals to rescue the auxotroph phenotype.
