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Cell bio
DNA replication repair and recombination
| Question | Answer | |
|---|---|---|
| self replication is the fundamental property of life (T/F) | True | |
| creation of DOlly from ___ nuclear transfer indicates that most of the information need for individual development. | somatic nuclear transfer | |
| what are the challenges of coping and keeping genetic information | continuity vs adaptation ; speed vs error rate ; repair or not to repair ; recombination | |
| what is mitosis used for | growth and repair , maintenance ( old to new) cells ; repair( damaged tissues ) | |
| what does it mean for DNA replication to be semi-conservative | each new strand can serve as a template for synthesis of new DNA strand | |
| what initiates DNA replication | ORC( origin of replication center) | |
| motor proteins which can unzip double-stranded DNA | DNA helicases | helicases binds to single - stranded DNA , using the energy from ATP hydrolysis , they push the other strand away |
| germline cells replicate at ___ rate or ____ accuracy than somatic cells | a much lower error rate or much higher accuracy | |
| DNA synthesis occurs only in the ___ direction | 5' to 3' direction | |
| ___ catalyzes the addition of nucleosides to the 3' -end of an existing oligonucleotide | DNA pol | |
| what are the two important feature of DNA polymerase | speed and primer | |
| de novo synthesis is ( error prone / not ) | error prone | |
| an endonuclease responsible for removing the RNA primer in lagging strand | Flap endonuclease 1 | |
| on lagging strand RNA primers are needed every | 200nucleotides | |
| an enzyme that stiches ligate the gap b/n okazaki fragments | DNA ligase | |
| proteins present at the fork of replication | DNA clamp , ssDNA binding protein , clamp loader ( replication factors ) | |
| what enzyme adds RNA primers | DNA primase | |
| what relaxes the supercoil adead of the unwinding strands | topoisomerase | |
| the error rate of DNA polymerization is 1 in__ and the total error per cell doubling is __ | 100,000 bases , 30,000 ( 3, 000,000,000 / 100,000) | |
| DNA polymerase has a domain with ___ activity , how much is the error rate now | exonuclease : 1 /10,000,000nt copied | |
| The cleavage of a mismatched nucleotide at the 5’ end will leave __ (n) | a monophosphate group at the 5’ end, | this blocks the addition of a new precursor unless a PP is added back to the 5 end |
| three steps that give rise to high-fidelity DNA synthesis | 5' - 3' polymerization ; proof-reading ; strand-directed mismatch repair | |
| why would DNA shorten | RNA primer at the end will be removed and the copy is short the size of the RNA primer | |
| the mistamch repair mechanism invloves __ and __ proteins | MUtL and MutS | |
| enzyme ___ maintains the length of genome | telomerase | |
| Telomerase is Expressed in | stem cells, such as embryonic stem cells, which proliferate indefinitely. | |
| telomerase is turned off in | most somatic cells, e.g. epithelia cells | |
| Telomere may function as | a molecular timer to prevent indefinite proliferation in somatic cells. Why? | |
| what 3 things are repaired in DNA repair | Errors in DNA replication ; "spontaneous" DNA alterations , induced mutaions | |
| nitrous acid is not an example of a mutagen | false ; it causes deamination | |
| the most frequent DNA damage : | depurination and deamination | |
| one of the consequences of DNA damage is strand breakage which entails | deletion of longer stretch of DNA ; translocation ; fusion | |
| what are visible DNA damage response to sunburn | transcriptional changes ( darkening of skin ) and apoptosis ( skin peeling ) | |
| list 4 DNA damage response | DNA repair , Cell cycle arrest , Transcription regulation , Apoptosis | |
| what are the "drill-n-fill" methods for repairing damaged DNA | base excision repair and nucleotide excision repair | |
| how does DNA repair double strand breaks | end joining and homologous recombination | |
| list enzymes is base excision repair (n) | DNA glycosylase : Apurinic/Apyrimidinic endonuclease ; DNA polymerase : DNA ligase | glycosylase removes the defective nucleotide , endonucleases create nicks ; polymerase adds new nucleotide ; ligase ligates |
| what is the quick and dirty way of DNA strand break repair (N) | broken ends processed by endonuclease and joined by DNA ligase | net result is : it will be repaired with deletion of nucleotides/ it becomes shorter |
| what is slow but flawless way of repairing DNA strand breaks | homologous recombination | |
| how is site specific recombination achieved/ what mediates it | Mobile Genetic Elements :: Transposons and Retroviruses | |
| what are the steps in DNA repair using recombination | 1. specific enzymes create a strand breakage 2. recombination can happen anywhere between two homologous DNA 3. process results in exchange over long stretches of DNA | |
| what are the ultimate parasite ( viruses) | MGEs(mobile genetic elements) | |
| 50% of human geneome is MGE (T/F) | True | |
| MGE's include Viruses(T/F) | True | |
| An inverted repeat (or IR) is | a sequence of nucleotides that is the reversed complement of another sequence further downstream. | |
| three mode of transposon movement | answer on slides | |
| Transposons move by (n) | cut-n-paste or copy-n-paste | non-replicative -- cut and paste ; replicative - copy n paste |
| the simplest mobile element is | DNA-only transposons | |
| what are the 3 major types of transposons | DNA only , Restroviral - like , non-retroviral | |
| Transposon movement : why is cut-n-paste non replicative and copy and paste is replicative | the total # of transposons did not change , where as in copy and paste the copy number of the transposons is increaed | |
| list steps in the cut-n-paste process | expression of transposase ; excision in the donor chromosome , insertion of short direct repeats in the target chromosome | |
| Transposons typically do not move unless | the cell is placed under stress, such as by irradiation or the during homologous recombination. | |
| transposon activation during stress may serve as | a source of genetic variation for evolution | |
| because retrotransposons can not be removed, their integration can be used | as molecular clock. | |
| the ultimate MGE, that is fully mobile | viruses | |
| significance of MGE (n) | Evolution , they are genetic parasites | ==>Accelerate evolution: gene duplication, Create genetic variation ==> Disrupt genome (cancer; hemophilia etc.)Suppressed by mutation, methylation, siRNA, piRNA etc. |
Created by:
jemalk
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