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NBME 22 Answers

nbme22/Block 4/Question#5 (51.3 difficulty score)
A new virus has been isolated that causes ...
Single-stranded positive-sense🔍
tags:

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 +4 
submitted by haliburton(192),
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cicrongad to ledmsetubl inlk ns ss ARN sutm yrrca RAN peeednntd NRA myersloaep (os atht is )uot.

laos, noccrgaid ot lelumdsetb terhe rae rvye fwe ds RNA ivsuesr, so to"ms ilkeyl" llwi be .ss osl,A dAntNeRdpne-e DAN prosameyel = reseveR .srrTntsiecpaa cinSe IHV is a ss sp NAR suriv whit ,RT 'tehyve edicsbdre na HIV .iusocn tno uesr eondby i.hst

nc1992  negative stranded can't be read by a translator so it needs to be transcribed into + first. Only then can it be used for protein. + is basically mRNA already. There's only one double stranded RNA family as far as I know- Reovirus so no encephalitis +8  



 +2 
submitted by welpdedelp(199),
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O,k os ARN petdnndee DAN eosrmayelp si rfo rrseeev apncerisats...tr glnsei dtdseran + sue NRA ntedndepe RAN alpoee.msyr Cna seemono ae?ixnpl

hyoid  The only thing I can think of is that HIV is a (+)-sense single-stranded RNA virus that relies on an RNA dependent DNA polymerase (reverse transcriptase) to synthesize DNA. +1  
haliburton  according to [medbullets link](https://step1.medbullets.com/step1-microbiology/104196/rna-viruses_) ns ss RNA must carry RNA dependent RNA polymerase (so that is out). also, according to medbullets there are very few ds RNA viruses, so "most likely" will be ss. Also, RNA-dependent DNA polymerase = Reverse Transcriptase. Since HIV is a ss ps RNA virus with RT, they've described an HIV cousin. not sure beyond this. +  
some0217710  Can’t think of any retroviruses outside of HIV and HTLV and they’re both +ssRNA +1  



 +1 
submitted by b1ackcoffee(26),

my problem with this, why can't it be similar to Hep B (circular DNA)? virus is new or hypothetical.

andro  Hep B - is " partially " Double stranded and not fully double stranded . Double stranded Circular does not necessarily denote Hep B even though the virus has a reverse transcriptase . I think they wanted you to pay attention to this . And besides the obvious fact that Hepatitis viruses cause inflammation of the Hepar ( liver) and not encephalon ( brain) +  



 +1 
submitted by kenyaboi(1),

the gotdamn trick here is HIV is single standed + sense "diploid". NBME writers are just fuckers. ughhhh




 +0 
submitted by hipster_do(6),
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I hintk shti wsa erfgrneri ot veerers psraas,ncittre nda hte ynlo wto uvsesri I ewkn thta ueds emht wree epHB dna ie/rvIeHuoVss.trr neiGv teh ocnttxe I ecipkd euIrvt/sHeVsiror chiwh aer SS + s.esne iTsh was dnki fo iedrw ghtouh neisc hte isvur swa “we”n ... but eI’v lndaree that w”“en ulyausl asemn vrye ltltei no shete ss.tte

yotsubato  "New" means made up fantasyland virus +5  
yotsubato  Also Hep B is a ssDNA virus that goes to RNA, then is reverse transcribed to dsDNA +  



 +0 
submitted by drschmoctor(69),

RNA depended DNA polymerase = reverse transcriptase (FA 20 p 38, under telomerase).

Given the virus has reverse transcriptase, it is likely a retrovirus (hepadnavirus also has reverse transcriptase).

Retroviruses are SS+ RNA viruses (FA 20 p 167)




 +0 
submitted by meddeku(0),
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aeeJsnpa isecletihnpa ivsru ocigcadrn ot .rD eGoolg cn)b(i

Glgeoo




 +0 
submitted by niboonsh(293),
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yM guses is ttah ehty rae fierergnr ot sveutrirRo HIHV/(VT)-L a slneig ndrsdaet ievoitsp seesn liaern RAN. ussiteeRvorr aer wknno to rryac rrevees cetisntrsraap eRnnNpde-Aed(t DlpyrAse)ea.Nm-o hTe eclenpahisti is wtah thewr em off uzc I cmollyaaautit ouhghtt of teh many vngteeia eessn NRA sveursi htat esacu tlesinhepaci (ielk earvnaisru or bvuryis)a.nu Aetrlapynp eerth aveh ebne a fwe casuse fo HTLV nsuiacg ilcep..ntasih.e aymbe stih si ahtw they eerw tgrnyi ot egt a?t Idk utb i tjus ptens awy oot much imet no iths mnda iuotnesq p1hgnb.///ce8rtnmilh5tsi.Cs7.7iw/:cw.matMo8/vcwn8l/pP




 -1 
submitted by jcmed(9),

As soon as I saw encephalitis I thought of Flaviviruses which are:

SS ⊕ linear Icosahedral including:

HCV,Yellow fever, Dengue, St. Louis encephalitis, West Nile virus aka meningoencephalitis and Zika virus

p. 167 First Aid 2018