MICROBIO 310: CHAPTER 10
45 Cards in this Set
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Mutation
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Heritable change in DNA sequence that can lead to change in phenotype
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Mutant
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A strain of any cell of virus differing from parental strain in genotype
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Wild-type strain
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Typically refers to strain isolated from nature
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Selectable mutations
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- Those that give the mutant a growth advantage under certain conditions
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Non-selectable mutations
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- Those that usually have neither an advantage nor a disadvantage over the parent
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Induced mutations
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- Those made environmentally or deliberately
- Can result from exposure to natural radiation or oxygen radicals
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Spontaneous mutations
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Those that occur without external intervention
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Point mutations
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- Mutations that change only one base pair
- Can lead to a single amino acid change in a protein, an incomplete protein or no change at all.
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Silent mutation
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Does not affect the amino acid sequence
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Missense mutation
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Amino acid changed; polypeptide altered
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Nonsense mutation
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Codon becomes stop codon; polypeptide is incomplete
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Frameshift mutation
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- Deletions of insertions that result in a shift in the reading frame
- Often result in complete loss of gene function
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Reversion
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Alteration in DNA that reverses the effects of a prior mutation
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Revertant
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-Strain in which original phenotype is restored
- Two types
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Same-site revertant
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Mutation is at the same site as the original mutation
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Second-site revertant
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Mutation is at a different site in the DNA
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Mutagens
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Chemical, physical, or biological agents that increase mutation rates
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Nucleotide base analogs
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Mutagen - resembles nucleotides
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Chemical modifications
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Induced by chemical mutagens
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Two main categories of mutagenic electromagnetic radiation
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- non-ionizing
- ionizing
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Non-ionizing
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-Purines and pyrimidines strongly absorb UV
- Pyrimidine dimer is one effect of UV radiation
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Ionizing
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(cosmic rays, X-rays, gamma rays)
- Ionize water and produce free radicals
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Three types of DNA repair systems
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- Direct reversal
- Repair of single strand damage
- Repair of double strand damage
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Direct reversal
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Mutated base is still recognizable and can be repair without referring to other strand
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Repair of single strand damage
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Damaged DNA is removed and repaired using opposite strand as a template
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Repair of double strand damage
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A break in the DNA, requires more error-prone repair mechanisms
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When DNA damage is large scale the cells use a different type of repair system -
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SOS regulatory system
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SOS regulatory system
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This system is more error prone. It allows replication to proceed and cell to replicate.
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Recombination
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Physical exchange of DNA between genetic elements
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Homologous recombination
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Process that results in genetic exchange between homologous DNA from two different sources
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Transformation
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Genetic transfer process by which DNA is incorporated into a recipient cell and brings about genetic change
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Electroporation
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Electricity can be used to force cells to take up DNA
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Transfection
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Transformation of bacteria with DNA extracted from a bacterial virus
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Transduction
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Transfer of DNA from one cell to another by bacteriophage, 2 modes.
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Generalized transduction
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DNA tom any portion of the host genome is packaged inside the virion
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Specialized transduction
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DNA from a specific region of the host chromosome is integrated directly into the virus genome
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Bacterial conjunction (mating)
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Mechanism of genetic transfer that involves cell-to-cell contact
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Donor cell
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Contains conjugative plasmid
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Recipient cell
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Does not contain plasmid
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F (fertility) plasmid
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- Contains genes that regulate DNA replication
- Circular DNA moleucle
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Sex pills is produced by who?
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The donor cell
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Merodiploid
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Bacterial strain that carries two copies of any particular chromosomal segment
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Complementation
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Process by which a functional copy of a gene compensates for a defective copy
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Trans - configuration
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Two mutations on different genes
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Cis - configuration
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Two mutations on the same gene
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Microbio 310: Exam 1