gene interaction Flashcards
What is inhibitory gene action (dominant epistasis I)?
Inhibitory Gene Action (13:3): Homozygous recessive hypostatic gene (iicc) produces the same phenotype as the masked condition.
What is the Bombay phenotype, and how does it affect blood type?
Definition: The Bombay phenotype occurs in individuals with two recessive alleles for the H locus (hh), meaning they cannot produce the H antigen, the precursor required for A and B blood antigens.
Without the H antigen, A and B antigens cannot form, so their blood tests as type O (technically Oh).
Even if they carry IA or IB alleles, these cannot be expressed due to the lack of the H antigen.
This is an example of recessive epistasis where hh masks the ABO blood group alleles.
Bombay phenotype individuals can only receive blood from others with the same phenotype (hh).
They can donate blood to anyone in the ABO blood group system because their red blood cells lack A, B, and H antigens.
Why does the Bombay phenotype (Oh) appear as O blood type? What is the main difference between regular O blood type and the Bombay phenotype?
Because hh prevents the production of the H antigen, so A and B antigens cannot form no matter whats at the other locus. reg O has ii and Oh is due to the second locus being hh bc H is the precursor needed to produce a and b antigens
What is complementation analysis, and when can it be used?
Complementation analysis determines whether mutations are in the same or different genes by testing if two mutants can “rescue” each other’s defects. It can only be used with loss-of-function (recessive) mutations, where both mutant genes must be expressed in the same cell to observe functional interaction.
Same gene: No complementation (mutants cannot rescue each other).
Different genes: Complementation occurs (mutants rescue each other).
How does complementation analysis help determine the number of genes and alleles involved in a phenotype?
Complementation analysis identifies how many genes are involved in a phenotype by grouping mutants into complementation groups:
Each group represents one gene.
Mutants that do not complement each other (show the mutant phenotype) belong to the same gene.
Mutants that do complement each other (show the wild-type phenotype) belong to different genes.
Each gene can have multiple mutant alleles, which are variations of mutations in the same gene.
Why is complementation analysis typically done with a homozygous recessive (homo rec) strain?
Complementation analysis is done with a homo rec strain to clearly observe whether mutations are in the same or different genes. In a homo rec strain, both alleles are defective, leading to a mutant phenotype. If the mutation is in a different gene, crossing with another strain can restore the wild-type phenotype (complementation). If the mutations are in the same gene, no complementation occurs, and the mutant phenotype persists. This makes it easier to interpret the genetic relationship between mutations.
