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NBME 23 Answers

nbme23/Block 1/Question#19 (35.5 difficulty score)
Unlike the DNA polymerases found in ...
Mistakes in transcription are not transmitted to progeny🔍
tags: biochem genetics 

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 +8  upvote downvote
submitted by krewfoo99(75),

So basically what this is saying that DNA will be transmitted to the progeny not RNA. So DNA will replicate in the G2 phase and transfer of DNA material to progeny will occur in the M phase. The RNA may be mutated and making defective products, but this will not transmit into the progeny, thus not affecting species survival based on RNA mutations.

bk2458  makes sense!! +  
almondbreeze  good work +1  
tyrionwill  the question asks the reason of no impact on its survival. if a protein translated from a wrong mRNA loses its function, how can we say the bacteria will still survive well? if there is always fatal error happened during mRNA transcription, and always leading to fatal dysfunctional protein, how can the bacteria and its progeny still survive? so the point will be whether the fatal errors will always happen during transcription? I dont know... +  
tyrionwill  actually FA and NBME seem to have made a wrong statement that RNA polymerase has no proofreading function. RNA polymerase has more fidelity to DNA than DNA polymerase by 2 ways: 1) highly selection of correct nucleotide, and 2) proofreading. (Jasmin F Sydow and Patrick Cramer, RNA polymerase fidelity and transcriptional proofreading: https://pure.mpg.de/rest/items/item_1940413/component/file_1940417/content) however, if survival of the species refers only to the reproduction of progeny, mRNA mutation has nothing with the progeny. +1  



 +4  upvote downvote
submitted by keycompany(268),
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ls3076  the phrasing of this explanation doesnt make sense to me. +3  
ls3076  oh wait sorry i just read it again. So instead of proofreading how are errors handled with RNA? +  
thomasburton  Think the point is basically although errors with RNA polymerase make make the bacterium not very good at infecting or killing or whatever it does not affect replication as it is not used during replication! +5  
almondbreeze  common sense asked in a very very convoluted way.. +  



 +1  upvote downvote
submitted by seagull(1112),
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eyngkl(bpw_d/aso.ooi//ewprtrg.o/tii:rgPniikiaio)dfeh

rHee si a lettli tbi on dprHrpeoofoi.nega ti hpsle

jcmed  I'm dropping out +  
drzed  This question doesn't have to do with proof reading, even though it is mentioned. It is just saying this: you can make all the misfolded proteins you want (e.g. proofreading can be messed up), but it has no relevance to the PROGENY. Why? The progeny of a cell is dependent on DNA replication only--so long as your DNA is perfectly replicated, the progeny will come out perfect. You don't need to worry about RNA to make DNA (unless you're HIV, of course!) +4