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NBME 22 Answers

nbme22/Block 4/Question#5 (56.0 difficulty score)
A new virus has been isolated that causes ...
Single-stranded positive-sense🔍
tags:

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 +4 
submitted by haliburton(209),
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aigdorncc to bmeteulsdl knil sn ss ARN mtsu racyr NAR ptnddeene ARN smrpeayloe s(o ttha is to)u.

ol,sa ogndrcaci ot leemudtslb ereth ear evry few ds ARN siursev, os omts" l"lkiey wlli eb ss. oAs,l dentneNdAeRp- DAN eayreolspm = evreRes rcarstpiTens.a cniSe IVH is a ss ps NAR ruvis tiwh ,RT 'htevye edircedbs an VHI uis.con nto urse obyend i.hts

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 +9  



 +2 
submitted by welpdedelp(219),
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,Ok os NAR tendepend NAD epmoselrya is orf rersvee t.nrrcsst.ia.pae snelgi rtsndead + sue NRA etddnpnee ANR l.yepaomers Can osoemne nexp?ila

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(35),

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(2),

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 htnki isth saw geinrrref ot reersve rtept,sraisnac nad het noyl owt evirsus I wnke hatt edsu ehmt reew HBpe nad V.rHsIt/seiuevorr Gvien the cotextn I ekicdp eVrrtusvero/IisH wchhi ear SS + enes.s Tsih swa iknd of wride tuohhg iesnc the risuv wsa ne“w” ... btu veI’ dnlreae atht “wn”e layulsu mesna yevr litetl no etesh et.sst

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(82),

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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psaeJean pnetecihials vusir raindccog ot Dr. gGoeol cn)bi(

glGoeo




 +0 
submitted by niboonsh(338),
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My gsesu is ahtt ehyt aer niergerfr to Reruvoisrt H)TIV-/VL(H a nlsige rneasdtd ivopitse ssnee alrnie N.AR rtiseorRuves ear wnkno to cayrr eervers tancresipastr d(tee-RNdpAnen -mNDrlpe)yaeA.os hTe lcseipneiath si hawt ewrht em fof zcu I ltyaamctuoail huthotg fo het amny veiegatn sense NRA surisev atth uscae chnsleetiaip l(kei useirnavra ro )uirsbau.nyv aptypelnAr eehtr heav enbe a wef sseauc fo VHTL ucgisan ae.iec.stniph.l eybam this si waht yeht ewer rtgnyi to etg ?at kId tub i just snpet way too hcmu teim no hsti nmda oteiunsq a/c:nMhl88v/5ocsbwCgwp/8ms/l.mnenh/.t.cit7/ti1rP.w7pi




 -1 
submitted by jcmed(13),

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