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NBME 22 Answers

nbme22/Block 4/Question#5 (50.8 difficulty score)
A new virus has been isolated that causes ...
Single-stranded positive-sense🔍
tags:

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 +3  upvote downvote
submitted by haliburton(191),
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cnoagcidr to smltdbulee iknl ns ss ARN tusm rryca RNA ednndetep RAN msyrpeelao (so htta si ou).t

los,a gaoicnrcd to tedlbmlues rtehe aer evyr ewf sd RAN rivess,u os tm"so ikleyl" ilwl be s.s ,loAs pteRndA-enedN AND esylamopre = vRreees pt.rarescisTan eicSn VIH si a ss ps NAR isvru wtih T,R hteyve' rbidesced na IVH scnui.o not rseu ebyndo itsh.

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 +7  



 +2  upvote downvote
submitted by welpdedelp(198),
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,Ok so NAR eptndndee NDA yoeprmslae si for evrrees isp.as.raret.nct lignse sderatdn + use RAN etnnpddee NRA yolem.aepsr naC meeoson lp?xeain

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  



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  upvote downvote
submitted by kenyaboi(1),

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




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I ntihk sthi asw fnrireger ot erveesr ttpscrsan,eair nad teh nyol tow iesrsvu I newk that sedu mhte were HBep nda r.erurevisos/tHIV vineG hte tnoxtce I ciekpd vreoVrIssiu/rtHe chiwh aer SS + .snese sihT asw nidk of ediwr thhugo ecnis hte uisvr swa we“”n ... ubt ’evI erlenad atht ”“wen lalsyuu smnea ryev tlltie no heset tes.st

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 +  



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  upvote downvote
submitted by meddeku(0),
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apnJeaes tspneiailech svriu ginccrdoa to .Dr oeGgol n(cbi)

olGoge




 +0  upvote downvote
submitted by niboonsh(284),
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yM ssuge si tath tyeh era rgnierfer to vutersorRi T/I(-L)VHVH a nesgli trdsaden oiisevpt senes aliner NR.A retveouRisrs ear onnwk ot cayrr seererv sctniaprarset end-dpRtn(eAeN Nee)ayorAD.-slpm Teh ncisleeptiah is whta ewhtr em off zuc I omyaalautcitl tthuogh of het myan tveaeing essen NRA vusersi atht ceuas tneiliasecph li(ke neuaaisrrv ro ).uranvsbuyi trppAleyan rethe ehva nebe a fwe easusc fo HTLV nigusac th.s.icnl.eipea mabey shti si whta ehty wree rytgin to tge at? Idk btu i jsut ptnes yaw oot uhcm eimt no hsit nmad siqtnuoe wnowe1v5ini/tc/p.ls/7C8rs.mnwtgclbt8iphmP//:/cM7.8a.h




 -1  upvote downvote
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