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Epistasis and Complementation quiz #1

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  • What is an example of epistasis?
    An example of epistasis is the Bombay phenotype in humans, where a recessive mutation in the H gene masks the expression of ABO blood type alleles, resulting in blood type O regardless of the ABO genotype.
  • What type of gene action occurs when one gene masks the effect of another gene at a different locus?
    Epistasis occurs when one gene masks or alters the effect of another gene at a different locus, affecting the phenotype.
  • What is an example of dominant epistasis in squash?
    In squash, the presence of a dominant W allele masks the effect of the D gene, resulting in a white phenotype regardless of the D gene's alleles. This is an example of dominant epistasis.
  • Which statement below defines epistasis?
    Epistasis is the interaction between two genes where the allele of one gene masks or modifies the phenotypic expression of another gene.
  • What is an example of recessive epistasis in a flower species?
    In a flower species, a recessive mutation in the W gene results in a white phenotype, masking the effect of the M gene, so both wwmM and wwmm genotypes produce white flowers. This is recessive epistasis.
  • What phenotypic ratio is expected from a dihybrid cross involving complementary gene action?
    The expected phenotypic ratio is 9:7, with 9 showing the dominant phenotype and 7 showing the recessive phenotype due to both genes needing a dominant allele for the trait.
  • How does a suppressor gene affect the phenotype in a genetic cross?
    A suppressor gene can reverse the effect of a mutation in another gene, often restoring the wild type phenotype and resulting in a 13:3 phenotypic ratio.
  • What is the difference between genotypic and phenotypic ratios in epistatic interactions?
    Genotypic ratios in epistatic interactions remain 9:3:3:1, but phenotypic ratios are altered depending on the type of epistasis, such as 12:3:1 for dominant and 9:3:4 for recessive epistasis.
  • What is a synthetic lethal interaction in genetics?
    A synthetic lethal interaction occurs when two single mutations are viable on their own, but their combination results in lethality, leading to a phenotypic ratio of 9:3:3 in observed offspring.
  • How do modifiers influence the expression of mutated genes?
    Modifiers change the degree of expression of a mutated gene, affecting the severity of the phenotype depending on the combination of mutations present.