Gene Structure 1 Flashcards
How can a gene be defined as a complementation unit?
Genes are a series of mutant alleles that fall into a single complementation group.
What is complementation?
Different mutations are partly or entirely cancelled out when they occur together, giving a functional genome.
What are complementation tests used for?
To see if recessive mutations that result in the same phenotype are on the same gene or on different genes.
How are complementation tests carried out?
Cross the homozygous mutant for mutation A with the homozygous mutant for mutation B. If mutations are on different genes, they will complement each other and the progeny shows the normal phenotype. If mutations are on the same gene, they affect the same functions and cannot complement each other- the progeny shows the mutant phenotype.
What type of genes are unsuitable for complementation testing?
Genes that have been alternatively spliced.
Describe T4 bacteriophage.
Virulent, capable of lytic acitivity. Virus infecting E.coli. 100-1000 progeny per hour per infected bacterium.
What is defined by complementation?
Gene relationship
How can gene order be determined?
The frequency of recombinants indicates the strength of linkage and the distance between genes. If genes are closer together they are more likely to be inherited together.
What is determined by a recombination test?
The location of 2 genes relative to each other.
What is seen in a recombination test if recombination has occurred?
Get double mutants and WT progeny. Plaques are only seen for WT progeny, must multiply the number of plaques by 2 to account for double mutants.
What is the recombination frequency in Benzer’s test?
((2 x plaques on K12)/plaques on strain B) x 100
Describe Benzer’s recombination test.
Infected E.coli strain B and harvested the lysate. Infected E.coli strain K12 with the lysate. Get double mutants and WT progeny.
What is defined by deletion mapping?
Approximate mutation regions.
Describe the test for deletion mapping.
Point mutation is crossed with a deletion mutant. If mutation lies within the deletion region, there is no recovery of WT function. If the mutation lies outside of the deletion region, WT function is recovered.
