MLS 558_Isolation of Mutant Flashcards
What is a mutation?
A heritable change in the base sequence of a genome
Mutations can affect the genetic blueprint of organisms.
What is recombination in genetics?
The process that creates new combinations of genes even in the absence of mutation
Recombination typically generates larger genetic changes than mutation.
What defines a mutant?
A strain of any cell or virus carrying a change in nucleotide sequence
A mutant differs from its parental strain in genotype.
What is genotype?
The genetic constitution of an organism
It is the underlying genetic makeup that may not be directly observable.
What is phenotype?
The observable properties of a mutant
Phenotype can include physical traits and behaviors.
What is a wild-type strain?
A strain isolated from nature that has not undergone mutation
Wild-type strains serve as a reference point in genetic studies.
What is the difference between selectable and non-selectable mutations?
Selectable mutations confer an advantage; non-selectable mutations do not
Selectable mutations can be easily identified under specific conditions.
What is a selectable mutation?
A mutation that confers a clear advantage under certain environmental conditions
An example is antibiotic resistance in bacteria.
What is a non-selectable mutation?
A mutation that does not confer any distinct advantage or disadvantage
An example is color loss in pigmented organisms.
What is a selection in genetic terms?
A growth condition that allows for the selective propagation of genetically marked cells
Selection is a powerful tool in isolating mutants.
What is screening in genetics?
The process of examining large numbers of colonies to identify mutants
Screening is used when selection cannot be applied.
What is an auxotroph?
A mutant with a nutritional requirement for growth
Auxotrophs cannot grow on minimal media without specific nutrients.
What is a prototroph?
The parent from which an auxotroph was derived
A prototroph can grow on minimal media.
What is the method of replica plating?
A technique used to detect nutritionally defective mutants
It involves transferring an imprint of colonies to a medium lacking nutrients.
How does the penicillin-selection method work?
Penicillin kills only growing cells, allowing for the isolation of auxotrophs
The parent cells are unaffected in a nutrient-lacking medium.
What is negative selection?
A selection method that is against the parental type, not for the mutant
The penicillin-selection method exemplifies negative selection.
What does a temperature-sensitive mutation affect?
An essential protein making it more heat-sensitive
This leads to inability to grow at high temperatures.
What does a cold-sensitive mutation cause?
Inactivation of an essential protein at low temperatures
Such mutants cannot grow at low temperatures that normally support growth.
What does a drug-sensitive mutation indicate?
Alteration of drug target or permeability to drug
This allows growth in normally inhibitory drug concentrations.
What results from a rough colony mutation?
Loss or change in the lipopolysaccharide layer
This leads to granular, irregular colonies instead of smooth ones.
What is a non-encapsulated mutant?
A mutant with a loss or modification of the surface capsule
This results in smaller, rough colonies.
What does pigmentless mean in the context of mutations?
Loss of an enzyme in the biosynthetic pathway leading to color loss
This results in the presence of different colors or lack of color.
What can mutations lead to?
Heritable changes in DNA sequence that can cause changes in phenotype
Selectable mutations are particularly useful in genetic research.
