Microbiology Topics (Ch7-Ch10)

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Polycistronic

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mRNA contains several genes

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Monocistronic

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mRNA contains only one gene

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Cistron

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Gene

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sigma (σ) factor

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Part of RNA polymerase that detects primer for Bacteria. Eukaryotes use transcription factors.

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Core Enzyme

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Part of RNA polymerase that completes transcription after primer binding.

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(-) Strand

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Stranf of DNA that serves as a template fr RNA synthesis.

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Promoter

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Nucleotide sequence to which RNA polymerase binds to initiate transcription.

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Terminator

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Sequence at which RNA synthesis stops.

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Directions of RNA synthesis

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5' to 3' (Nucleotides added to 3' end)

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The Direction of Translation

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5' to 3'

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The region before the AUG start codon on an mRNA.

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ribosome-binding site

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Polyadenylation

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Polyadenylation is the addition of a poly(A) tail to an RNA molecule. The poly(A) tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA which only has As. In eukaryotes, polyadenylation is part of the process that produces mature messenger RNA (mRNA) for translation.

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RNA Splicing

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Splicing is a modification of an RNA after transcription, in which introns are removed and exons are joined

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What are the sizes of the units make up the prokaryotic ribosome?

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30S + 50S = 70S

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Corynebacterium diphtheriae

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Bacteria that produces Dipthera toxin. The toxin binds to and inactivates one of
the elongation factors of eukaryotes.

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Bioinformatics

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Analysis of nucleotide sequence data.

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Open reading frame

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Stretches of DNA, generally longer than 300 bp, that begin with a start codon and end with a stop codon

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Operon

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An operon is a unit of key nucleotide sequences of DNA including an operator, a common promoter, and one or more genes.

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Repressor

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Blocks transcription of a gene by binding to its operator.

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Operator

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A segment of DNA that a regulatory protein binds to. Usually downstream of the operon.

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Corepressor & Inducer

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These act alongside a repressor to either block transcription or induce it. Both bind to a repressor.

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Activator

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Protein that, when bound to the activator-binding site upstream to a DNA promoter, activates transcription.

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lac operon

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Consists of three genes, a promoter, and both repressor and activator binding-sites.

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Diauxic growth

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Example: When E-coli utilize glucose until it runs out, then stop growth, and then resume growth by utilizing lactose. Glucose represses the enzymes of lactose degradation.

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Catabolite Repression

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Example: Glucose represses the enzymes of lactose degradation. Occurs in diauxic growth.

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Quorum Sensing

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Bacteria sense the density of cells within their populations and module their actions.

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Antigenic Variation

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The ability of certain bacteria to change markers on their external surface.

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Expression Locus

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When one of many allelic genes enters this part of the chromosome it is expressed.

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Auxotroph

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A mutant bacteria which cannot survive without the addition of an exogenous growth factor.

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Prototrophs

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Bacteria that can survive without the addition of any growth factors.

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Missense Mutation

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A mutation in which one amino acid is changed into another.

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Point Mutation

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A mutation in which only one DNA base is changed.

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Leaky Mutation

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A missense mutation that results in a partially functional protein.

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Nonsense Mutation

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A mutation in which an amino acid is changed to a stop codon. Most proteins with such mutations are not functional.

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Knockout/Null Mutation

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A mutation that results in a completely non-functional protein.

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Frameshift Mutation

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When a number of amino acids that is not a multiple of 3 is added or removed a frameshift mutation results. Most are knockouts.

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Transposons

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Segments of DNA that can move from one postition to another in a DNA molecule (transposition). Usually knocks down expression of the target gene.

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Alkylating Agens

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Mutagens that add alkyl groups onto purines and pyrimidines. This alters their hydrogen bonding properties.
Example: Nitrosoguanidine

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Mutagen

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Induces mutations in the DNA sequence of an amino acid.
Example: Nitrous acid converts cytosine to uracil.

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Base Analog

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A compound that resembles a purine/pyrimidine base such as 5-bromouracil. Its hydrogen binding is different from the base it replaces and occasionally base-pairs with the wrong base.

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Intercalating Agent

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Inserted between two DNA bases thereby spreading them apart. Often, an extra nucleotide is added in the strand being synthesized resulting in a frameshift mutation.

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Ethidium Bromide, for example.

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Insertion Mutation

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Occurs when a transposon is inserted into a gene causing a knockout mutation.

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Thymine Dimers

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An intrastrand DNA bond usually formed upon exposure to UV radiation.

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Proofreading

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DNA polymerase excises and replaces an incorrectly placed base with the correct one after synthesis. It detects the problem based on the poor hydrogen bonding of the mismached pair.

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Mismatch Repair

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An enzyme removes a string of nucleotides surrounding a mismatch. This allows DNA polyermase and DNA ligase to repair the strand.

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Photoreactivation (Light Repair)

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Occurs when an enzyme uses light to break Thymine dimers on DNA previously induced by exposure to UV light.

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Excision Repair (Dark Repair)

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The bases containing Thymine dimers along with the bases surrounding them are excised. The DNA is then repaired by DNA polymerase and ligase.

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SOS Repari

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A secondary or last resort method of DNA repair that bacteria employ in the case of a high amount of UV damage. It's able to skip damages segments but is also very error prone.

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Combination Therapy

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A treatment strategy in which multiple drugs are used at the same time to prevent the possibility of resistance formation.

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Conditional Lethal Mutant

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A mutant with mutations in essential genes needed for survival The mutations are only apparent in certain conditions.

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Lateral Gene Transfer

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Transfer of genetic material between bacteria.

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Vertical Gene Transfer

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Transfer of genetic material from parent to daughter cell.

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Homologous Recombination

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When a single strand of DNA from one bacterium transfer to another bacterium and integrates into its genome at a homologous gene.

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DNA-mediated Transformation

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Naked DNA from ruptured or dead bacteria can enter growing ones and integrate into their DNA replacing the homologous genes.

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Competent Cells

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Cells with the ability to take up naked DNA and integrate it into their genome.

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Electroporation

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A method in which an electric current makes pores in the cell membrane of bacteria thereby inducing artificial competence.

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Transduction

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A process in which horizontal gene transfer occurs through the actions of a bacteriophage.

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Generalized Transduction

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The process in which a bacteriophage releases deoxyribonuclease to break down both its DNA and its host DNA. The host DNA is taken up and incorporated into the next infected cell.

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Specialized Transduction

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Occurs during the lysogenic phase of the phage life-cycle. A phage may excise part of the nearby host DNA when it enter the lytic phase.

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Conjugation

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Bacterial recombination via a sex-pilus and plasmid transfer.

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Hfr (High Frequency Recombination)

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When an F plasmid becomes integrated into the bacterial chromosome.

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Insertion Sequence

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A sequence of nucleotides that allows a transposon to insert into a chromosome. Usually an inverted repeat.

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Modification Enzyme

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An enzyme that methylates adenines and cytosines on a DNA molecule to protect it from its own restriction enzymes.

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Vector

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The bacterium that incorporates a DNA insert.

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Reporter Gene (Reporter)

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A sequence inserted into a gene that produces a readily detectable molecule when the gene is expressed.

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Probe

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A probe hybridizes to a specific nulceotide sequence in a DNA molecule and gives off a signal (radioactive, fluorescent, etc.)

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Southern Blot

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Resriction fragments are separated by size and then probed.

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Colony Blot

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Cell is lysed, DNA is denatured, and restriction enzymes cut it up. A probe is then added which hybridizes with the target sequence.

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Restriction Fragment Length Polymorphism (RFLP)

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Occurs when restriction enzymes are added to a mixture of bacterial DNA. The produced restriction fragments will be of different lenfth for each bacterial DNA.

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Fluorescent In SItu Hybridization (FISH)

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A probe is added to intact cells of a microscope slide and fluorescence is detected. For prokaryotes, the probe binds rRNA and can differentiate between many different species.

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Selectable Marker

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A sequence inside a plasmid vector which, when interrupted by an insert, changes the phenotype of the bacterial cell.