Chapter 8 – Microbiology Test Questions – Flashcards
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| genetics |
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| the science of heredity |
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| genome |
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| all the genetic information in a cell |
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| chromosomes |
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| structures that contain DNA, physically carry the hereditary information |
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| genes |
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| segments of DNA that code for functional proteins |
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| base pairs |
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| adenine to thymine (or Uracil), cytosine to guanine |
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| genetic code |
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| the set of rules that determines how a nucleotide sequence is converted into the amino acid sequence of a protein |
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| genotype |
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| the genetic makeup of an organism, represents the potential properties |
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| phenotype |
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| actual, expressed properties |
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| genomics |
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| sequencing and molecular characterization of genomes; can be used to identify strains of bacteria/viruses |
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| DNA replication |
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| one double stranded parental strand divides into two identical double stranded daughter strands; is semi-conservative: each daughter strand contains one of the parent strands |
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| DNA adds in the _______ direction |
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| 3' to 5' |
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| Lagging strand |
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| Okazaki fragments |
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| DNA Gyrase |
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| relaxes supercoiling of DNA |
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| DNA helicase |
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| unwinds DNA double strand |
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| DNA polymerase |
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| synthesizes new DNA/proofreads and repairs DNA |
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| DNA primase |
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| adds RNA primers for DNA polymerase |
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| RNA polymerase |
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| transcribes DNA into mRNA |
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| DNA ligase |
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| connects Okasaki fragments on the lagging strand |
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| DNA error |
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| 1 in 10 to the 10 bases |
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| Bacteria DNA replication |
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| bidirectionally because of circular DNA, had origin of replication and termination |
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| Transcription |
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| RNA polymerase binds to promotor site, translates DNA gene sequence until kicked off by the terminator |
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| Translation |
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| occurs in ribosomal complex: large and small ribosome subunits +mRNA + tRNA with attached amino acids; mRNA code is read in triplets |
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| codon |
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| triplet of amino acids |
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| Anticodons of tRNA are _______________ of mRNA |
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| complementary |
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| sense codons |
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| code for amino acids |
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| nonsense codons |
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| don't code for amino acids |
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| There are ___ sense codons but only ____ amino acids |
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| 61; 20 |
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| mRNA has introns spliced out before mRNA leads the nucleus. Eukaryotes or Prokaryotes |
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| Eukaryotes. |
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| Lack of nucleus allows simultaneous transcription and translation. Eukaryotes or Prokaryotes |
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| Prokaryotes. |
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| Regulatory Gene |
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| before the operon; it encodes for the repressor protein molecule that switches inducible or repressible operons 'on' or 'off' |
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| operon |
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| consists of the control region (promotor, and operator) and the structural gene region (part that is transcribed); the operator serve as a point of attachment for the repressor protein |
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| repression |
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| a mechanism that inhibits gene expression/protein synthesis |
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| induction |
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| a process that turns on the transcription of a gene |
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| inducible operon |
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| can be switched from a default 'off' or 'on'. It uses a REPRESSOR protein to inhibit RNA polymerase transcription; the default position for the REGULATORY gene is 'on'. In the presence of an inducer molecule/protein or 'substrate' the repressor protein is inactivated and detaches from the operator sequence on the DNA. This allows transcription of the structural gene by RNA polymerase to occur. |
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| repressible operon |
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| can be switched from a default 'on' to 'off'. Uses a corepressor molecule to activate the repressor protein. REGULATORY gene is still turned on but the protein product is inactive (not bound to the operator) until it is attached to the corepressor. The addition of the corepressor allows the repressor protein to bind to the operator, which inhibits transcription. |
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| positive regulation |
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| though a gene may not be inhibited by a repressor attached to an operator region, RNA polymerase may still not bind without the help of another protein. This other protein is activated by another molecule in the environment, which activates it and allows it to bind to RNA polymerase. This aids RNA polymerase in binding to the promotor region so transcription can occur. Helps decrease energy loss on transcribing unneeded gene sequences. |
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| mutation |
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| a change in the base sequence of DNA |
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| Base substitution (mutation) |
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| most common type, a single base at one point in the DNA sequence is replaced with a different base; doesn't necessarily cause change in protein sequence because 61 codons code for only 20 amino acid types. |
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| Missense mutation |
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| results in an amino acid change in the protein |
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| nonsense mutation |
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| base substitution results in an earlier stop codon, results in a shorter protein |
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| frameshift mutation |
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| one or few DNA nucleotide pairs are deleted/inserted; changing the 3 codon reading frame |
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| spontaneous mutation |
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| occur spontaneously in teh absence of mutation-causing agents; occurs because occasional mistakes made during DNA replication (can be base substitution or frameshift |
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| mutagens |
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| agents in the environment that directly or indirectly bring about mutations |
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| mutation rate |
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| the probability that a gene will mutate when a cell divides, usually increased with the presence of mutagens |
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| identifying mutagens |
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| can be tested/selected for based of phenotype |
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| positive (direct) |
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| detects mutant cells by rejection of the non-mutants |
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| negative (indirect) |
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| involves replica plating; mutant lose ability to synthesize something so it cn grow on certain mediums that none mutants can |
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| auxotroph |
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| any mutant microbe having a nutritional requirement that is absent in the parent |
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| carcinogen |
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| causes cancer; many mutagens are carcinogens |
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| Ames Test |
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| tests for carcinogens; suspected carcinogens/mutagens identified if they cause a change in bacteria samples which allows them to grow when they wouldn't have otherwise; the more mutant colonies the stronger the carcinogen/mutagen |
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| Vertical Gene Transfer |
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| information passed from one generation to teh next to the next, one cell divides into two identical daughter cells |
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| gene recombination |
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| the exchange of genes between two DNA molecules to form new combinations of genes on a chromosome; involves chromosome crossing over |
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| horizontal gene transfer |
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| genetic information transferred between cells for the same generation "recombination", often done through DNA plasmids, viruses, or sex pili; transfer involves 'donor' and 'recipient' cells |
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| transformation |
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| genes are transferred from one bacterium to another as 'naked' DNA; *heat killed bacteria still have DNA that can be transferred to other bacteria Ex. if mouse is injected with heat killed pathogen, the mouse will live. If mouse is injected with head killed pathogen and live non-pathogenic microbes, genetic transformation will occur turning the non-pathogens into pathogens and the mouse will die. (Griffith's experiment) |
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| Griffith's experiment |
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| If mouse is injected with heat killed pathogen, the mouse will live. If mouse is injected with head killed pathogen and live non-pathogenic microbes, genetic transformation will occur turning the non-pathogens into pathogens and the mouse will die. |
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| conjugation |
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| horizontal transfer also, occurs with plasmids; F factor-fertility, plasmids can be transferred from an F+ to F- cell via sex pili making two F+ cells; |
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| F+ |
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| plasmid present in cell |
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| F- |
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| plasmid absent in cell |
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| Hfr |
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| plasmid is incorporated into the cell's chromosomes |
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| transduction |
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| 3rd horizontal transfer; involves bacteriophages, bacteria DNA is transported from one cell to anotehr by the virus infection |
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| conjugative plasmids (special plasmids) |
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| carries genes for sex pili/ for transfer of the plasmid between cells |
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| dissimilation plasmids (special plasmids) |
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| code for unusual enzymes that aid in metabolism |
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| resistance factors (R factors) |
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| plasmids that enable bacteria to be more resistance to certain drugs; can be resistance transfer factor or R-determinant |
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| RTF |
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| resistant transfer factor (genes for plasmid conjugation/replication |
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| R-determinant |
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| genes for more drug resistance |
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| transposons |
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| small segments of DNA that move from one region of DNA to another; occurs in all organisms; occurs rarely; all carry the information for their own translocation |
