BIO204 - Chapter 7 (Microbial Genetics)
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40 terms
Terms | Definitions |
|---|---|
 genetics | the study of inheritance and inheritable traits as expressed in an organism's genetic material |
| genome | the entire genetic complement of a cell or virus composed solely of deoxyribonucleic acid & ribonucleic acid, including both its genes and nucleotide sequences that connect genes to one another; a code of info for making things; |
| genes | specific sequences of nucleotides that code for polypeptides or RNA molecules |
| genes are contained in | 1 chromosome and plasmids |
| plasmids | small molecules of DNA that replicate independently of the chromosome; usually circular and smaller than a chromosome; carry info for its own replication and often for one or more non-essential cell traits, including disease-causing genes |
| how does DNA duplication in bacteria differ from that of eukaryotes? | it is a continuous process |
| what is one major trait that accounts for microbial adaptability? | mutation |
| reproductive processes require a lot of | energy, carbon, enzymes |
| replication | a continuous anabolic polymerization process for the synthesis of new DNA from energy-rich monomers called deoxyribonucleotides |
| deoxyribonucleotides | DNA nucleotides with 3 phosphate groups linked together by 2 high energy bonds (dATP, dCTP, dTTP, dGTP) |
| replication: the process overview | a semi-conservative, bidirectional pathway of chromosomal duplication starting at an initiation point and ending 180 degrees away at the termination point |
| origin of replication | aka OriC; a spot on the genetic material indicated as the starting point |
| replication fork | the division at the initiation site that separates the 2 directions leading to the termination point |
| replication: the process in detail | proteins expose the DNA helix and helicase unzips the DNA molecule at OriC by breaking the H bonds b/w complementary bases; primase synthesizes a short RNA molecule at initiation to indicate direction; DNA polymerase binds to each unzipped strand and replicates simultaneously with the other polymerase, 1 being the leading strand that reads continuously and 1 lagging that creates okazaki fragments that ligase ties up later; then proof-reading and repairs occur before it's finished |
| replicons | DNAs suitable for replication based on their having an origin of replication; all plasmids and chromosomes have these |
| gyrases | enzymes used to untwist the helix during replication by grabbing it once separated and spinning it backwards |
| replication enzymes are halted by | inhibitors (analogues) |
| transcription | the synthesis of RNA from DNA in 4 main types (RNA primer, mRNA, rRNA, tRNA); the process whereby information is copied into RNA information by dsDNA-dependent RNA polymerase, requiring a template dsDNA, high energy ribonucleotide triphosphates, and RNA polymerase |
| transcription: initiation, elongation & termination | RNA polymerase binds to promotors forming a stable RNApolymerase-DNA complex to locally unzip and unwind the DNA without the aid of helicase or a primer, then process starts 10 nucleotides away by reading the uncovered base information; then it's either self-termination or rho-dependent termination |
| self vs. rho dependent termination | when RNA polymerase transcribes a terminator sequence vs. when a termination protein (rho) binds to RNA sequences near the end of a transcript and moves toward RNA polymerase to force it off the DNA strand |
| sigma factor | a polypeptide subunit of RNA polymerase that is necessary for recognition of the promoter in transcription |
| promoters | specific nucleotide sequences located near the beginning of a gene that bind to RNA polymerase to start transcription |
| translation | the process of initiation, elongation/translocation, & termination whereby ribosomes use the genetic information of nucleotide sequences from mRNA to synthesize proteins |
| translation: the process | molecules of tRNA deliver preformed amino acids as anticodons to a ribosome at site A which assembles them in a specific order according to the instructions from DNA delivered via mRNA (after transcription), attaching them to a growing P site (translocation) and allowings pace for the next aa to move in |
| translation: codons | groups of 3 nucleotide bases that either code for an amino acid (61) or a stop (3--> UAA, UAG, UGA); AUG is start/methionine (one of the 61) |
| release factors | what actually halt elongation in translation by recognizing stop codons and modifying the larger ribosomal subunit to sever the polypeptide from the final tRNA |
| genote | either endo or exo; the physical structures that contain the genetic information of a genome (the intangible message) |
| sense vs. antisense strands | strands of DNA not read in transcription, a mirror image of the RNA being synthesized (but with T instead of U) vs. the strand of DNA that is read, a complement of the synthesized RNA |
| what is the most commonly targeted process by humans to kill pathogens? | translation |
| eukaryotic vs. prokaryotic translation | eukaryotes complete mRNA in the nucleus and must export it to the cytoplasm; interspersed with junk vs. bacteria produce mRNA in the cytoplasm for instantaneous translation; just the necessities |
| gene recombination | the exchange of nucleotide sequences between two DNA molecules and often involves segments that are composed of identical (or nearly) nucleotide sequences |
| recombinants | DNA molecules that contain new arrangements of nucleotide sequences as a result of recombination |
| vertical vs. horizontal gene transfer | passing genes to the next generation vs. to the same generation |
| there are ___ mechanisms for gene recombination | 3: transformation, conjugation, transduction |
| transformation | the process by which a competent cell (one that expresses competin, near the end of logarithmic phase) accepts and internalizes exogenous DNA more efficiently to potentially integrate it into the chromosome |
| transformation: origins | Griffith, Avery & McCloud discovered that diplococcus pneumonia produces smooth, fatal colonies and rough, harmless colonies, but when dead S & live R are injected into mice, the mice still die because the R integrate the deadly S traits and become lethal |
| conjugation | involves the use of a sex pilus in order to transfer genetic material from F+ (with a sex pilus) to F- (no sex pilus organisms); limited to gram negative; linear unidirectional replication that can involve the inheritance of resistance |
| F' organisms | F+ organisms who have joined with another plasmid; when conjugation occurs, either F' and F- or 2F' are produced, depending on the time spent in conjugation (F' trait is transferred last, so if it doesn't last long enough it won't be F') |
| HFr organisms | high frequency recombinant cells; F+ cells that have been incorporated into the chromosome; HFr x F- = Hfr & F-, diploid for some genes |
| transduction | this is accomplished by viruses when they infect a cell and replicate within it to destroy the host cell DNA; newly formed virus particles may pick up a fragment of the host DNA and bring it into cells they later infect |
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