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30 Cards in this Set

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What are selectable mutations?
mutations giving a growth advantage like antibiotic resistance
What are non selectable mutations?
mutations having neither an advantage nor a disadvantage, detected by screening
What types of organism do replica plating identify?
Auxotrophs: cells with a nutritional requirement for growth
What are induced mutations?
mutations made deliberately or as a result of env. influence (ex. exposure to natural radiation)
What are spontaneous mutations?
mutations occurring without external intervention, like mistakes in DNA replication/repair
What is genetic engineering?
involves introduction of specific mutations (site-directed mutagenesis)
What is reversion?
Alteration in DNA that reverses the effects of a prior mutation
What is a revertant? What are the two types?
strain in which original phenotype is restored
1) Same site revertant: mutation at same site as original mutation, reproduced WT
2) Second site revertant
What is a second site revertant
Mutation is at a different site in DNA, but still restores WT Phenotype.
Called a suppressor mutation
which genome DNA virus/RNA virus has a higher error rate?
RNA genome
What are mutagens?
Chemical, physical or biological agents that increase mutation rates
What are the different classes of chemical mutagens?
1) Nucleotide base analogs (resemble nucleotides, DNA can't bp correctly)
2) Chemical mutagens-induce chemical modifications
3) Chemical mutagens causing frameshift mutation
What is an example of a chemical mutagen inducing chemical modification?
Nitrosoguanidine
What is an example of Chemical mutagens causing frameshift mutation
Intercalating agents like acridines
What forms of radiation are mutagenic?
1) Non-ionizing (UV): purines & Pyrimidines absorb UV, produce dimers
2) Ionizing (X-ray, cosmic ray, gamma ray): ionize water and produce free radicals damaging cells
What type of radiation uses higher energy?
Ionizing radiation (X-ray, cosmic ray, gamma ray)
What are three types of DNA repair systems?
1) Direct reversal: mutated base is recognized by enzymes, repaired without referring to other strand.

2) Repair of ss damage: damaged DNA removed and repaired using opp. strand as template

3)Repair of ds break: Require more error-prone mechanism--> If break can't be repaired-cant replicate-die
What is the Ames test?
Detects an increase in mutations in a bacterial strain treated with suspected mutagen which are usually carcinogenic

Reversion of auxotrophic strains: revertants can grow on minimal medium, colonies can be counted
What is recombination
Physical exchange of DNA between genetic elements (Chromosomes, plasmids, virus, free DNA fragment)
What is homologous recombination?
genetic exchange between homologous DNA regions from 2 different sources- homologous DNA regions have a common ancestor, contain similar seq and genes
What is a competent?
cells capable of taking up DNA and being transformed.
What conditions are needed for a cell to become competent?
Some bacteria are naturally competent. Others need to be treated with: calcium, cold temp, electroporation (electric voltage spike)
What is transduction?
Transfer of DNA from one cell to another by a bacteriophage (virus)
What are two types of transduction?
1) Generalized: DNA from any portion of the host genome is packaged inside vision

2) Specialized: DNA from a specific region of host chromosome is integrated directly into virus genome.
What types of viruses are involved with generalized transduction?
Both temperate and virulent
What types of viruses are capable of specialized transduction?
Temperate virus: DNA of temperate virus excises incorrectly, takes adjacent host genes along
What is bacterial conjugation?
Mechanism of genetic transfer involving cell to cell contact.
What does the donor cell and recipient cell contain in bacterial conjugation?
Donor=Contains Conjugative plasmid (F+)
Recipient=No conjugative plasmid
What are essential features of conjugation?
1) Sex pillus (produced by donor cell, encoded by F+ plasmid)
2) DNA synthesis by rolling circle replication necessary for DNA transfer
What features does the F plasmid contain?
1)Circular DNA
2) Genes regulating DNA replication
3) Transposable elements that allow plasmid to integrate into host chromosome
4) Tra genes that encode transfer functions