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MMBIO Quiz 6
| Term | Definition |
|---|---|
| DNA replication is both | semi-continuous and semi-discontinuous |
| each daughter strand is hybridized to a | parent strand |
| half old | half new |
| semi-conservative method guarantees | accuracy and preserves continuity |
| pulse-chase experiment | add a "pulse" of a labeled substance (radioactive labeled aa/nucleotides) label in then incorporated into the newly synthesized molecules (protein, RNA, DNA) remove labeled and add regular molecules "chase" watch and track the labeled molecules |
| a pulse-chase experiment tells you | where things go in a cell, how they move in a cell, how new things are made and the rate of their production, how long things last |
| Meslson-Stahl pulse-chase experiment showed that | DNA replication is semi-conservative |
| not conservative | old DNA stays together, new DNA is seperate |
| not dispersive | old and new DNA are mixed along each strand |
| Meselson-Stahl steps | started bacteria cells in heavy nitrogen shifted bacteria to lighter/regular nitrogen centrifuge to separate by weight result: after one replication was intermediate density (each had one heavy and one light strand) |
| leading and lagging strand | 5 to 3 okazaki fragments |
| DNA origin of replication (ori) | an AT rich region of DNA where replication beings |
| initiator (DnaA protein) | recognizes ori sequences and bind to them starts to unwind DNA recruits other proteins to the site |
| helicase | breaks hydrogen bonds to open DNA makes DNA into a suitable template molecule makes replication bubble |
| single stranded DNA (ssDNA) and binding proteins (ssBs) | keeps DNA un-annealed (separated) to use as a suitable template DNA naturally wants to bind so these keep it apart |
| primase (DnaG) | synthesizes small primers made of RNA to start the process provides 3' - OH ends for extension |
| primers | where DNA polymerase knows where to start building |
| DNA polymerase | adds nucleotides (pre-existing 3'-OH required) uses template strand to know what nucleotide to add |
| DNA Polymerase III | one cop[y does all of the DNA synthesis on the leading strand one copy does most of the DNA synthesis on the lagging strand proofreading capacity - detects mistakes, cuts them out, fixes them |
| Rnase H | finds RNA primers on the DNA molecule and removes the RNA nucleotides |
| DNA polymerase I | fill in the gaps created as RNA primers are removed at the start of okazaki fragments on the lagging strand (so it only does a small amount) also has proofreading capacity |
| ligase | connects the okazaki fragments together |
| topoisomerase I | nicks one strand of DNA to relieve pressure made as the DNA gets unwound and the tension gets too high |
| complete DNA replication steps | initiator binds to ori and unwinds DNA helicase separates the two strands SSB keeps them apart topoisomerase relieves tension primase makes primer DNA polymerase III synthesizes DNA DNA polymerase I removes primers and fills gaps ligase seals it |
| on the lagging strand the final RNA primer at the very end cannot be replaced because | there is no 3' OH to extend from |
| this means each time a cell divides, the newly made strand is | slightly shorter |
| telomeres | repeated DNA sequences at the ends of chromosomes to protect the essential genes when the DNA shortens |
| telomerase | extends the ends of newly replicated linear chromosomes does reverse transcriptase activity |
| error rate of DNA polymerase is super low | 1 in 10^4-10^5 nucelotides |
| proofreading and mismatch DNA repair corrects | 99.9% of the mistakes in DNA damage |
| permanant errors occur 1 in every | 10^8 - 10^11 bp (and there is 6x10^9 bp of DNA per diploid cell) |
| mismatch | a base is changed, and so the pairing base is changed as a result too |
| pyrimidine dimers | cause by UV light from sunlight |
| hydrolytic cleavage | caused by water |
| alkylation | enzyme adds alkyls |
| DNA insertions | viruses and transposons |
| double-stranded breaks | X rays, gamma rays |
| pyrimidine dimers | intra-strand cross-links they can form when DNA is exposed to UV light |
| UV light causes destabilization of chemical bonds | the bonds reform they can assume improper configuration |
| intra strand | within the same strand between bases on the same strand |
| thymine dimer | covalent double bond between the C5s and C6s of the thymine |
| thymine-cyotsine photoproduct | covalent bond between the C4 and C6 of a thymine and a cytosine |
| in dimers, hydrogen bonding is disrupted, resulting in a | bubble |
| dimers make a ____ in the DNA helix | kink |
| dimers pull the bases closer making it harder to | separate the bases |
| dimers act as ______ and block replication | roadblocks |
| hydrolytic cleavage can disrupt 3 types of bonds | phosphodiester bonds (sugar and phosphate bond) N-glycosyl bonds (base and sugar) exocyclic amine group to base bond |
| phosphodiester bonds and hydrolytic cleavage | single strand breaks (nicks) in the backbone easily fixed with ligase |
| N-glycosyl bonds and hydrolytic cleavage | causes depurination removes an entire purine base |
| depurination happens 10,000 times every day per cell meaning DNA repair enzymes must fix | 10^17 of these per day |
| bonds linking amine group and base and hydrolytic cleavage | causes deamination removes amine group, potentially change base |
| alkylation | adding on an alkyl (hydrocarbon) cytosine --> 5-methylcytosine |
| cytosine after deanimation loses the amine group leaving a carbon exposed that | binds to an oxygen, becoming uracil |
| 5-methylcytosine undergoes deanimation and loses the amine group so it binds to an oxygen and | becomes a thymine |
| reactive oxygen species (ROS) | oxygen that have an unpaired electron and are highly reactive |
| different bases can now H-bond with an extra OH and O groups which causes | mutations |
| inter-strand | between two bases on different strands |
| ionizing radiation | X rays and gamma rays can induce double-stranded DNA breaks cell doesn't know which to attach to which - random joining |
| most susceptible to DNA damage | cells that divide quickly (and don't have enough time to fix mistakes) |
| purposeful DNA damage | drug testing/cancer research studying repair mechanisms |
| transposons | cut itself out of one place in DNA, insert itself elsewhere |
| retroviruses | inserts itself into the host genome |
| pros vs cons of DNA damage | pros: antibodies, evolution, gametes/meiosis cons: cancer, diseases, cell death |
| mutagen | something that causes mutations |
Created by:
anyasalmon