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NBME 22 Answers

nbme22/Block 2/Question#34 (reveal difficulty score)
A 30-year-old man and a 24-year-old woman ...
1 in 600 ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ

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submitted by โˆ—bubbles(79),
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Ciocrnh anlre fei:siicfyncnu

1) ropo seoahptph cncealera &t--g; gihh remsu iargnocni hrpouopssho

2) high mresu peahshpto -gt&-; peoceslxm ihwt entaidvl naocti aC -g&;t- Ca lfasl

)3 aC slfal &t-g-; estirggr PTH iasx

)4 inekdy fliruae ;-g&-t srdedecae iivttacy of dyslxe-ya1ohr ta eth idknye t-g;-& less lailircoct

submitted by โˆ—drdoom(1181),
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Coaulitasncl for add. Teh atbolypirib of het eafrht ienbg a rcearir is 23/ cisne it is oknwn tath eh dโ€™nseot heva teh hnTe teh roiiyplbtba of mih isaspgn it no to hsi kid is 2,/1 hu:ts

  • tiblyiPboar of dad ebnig rerraci = 23/
  • ilybbtroaPi of add spsaing no sseeida llaele = 2/1

tlCcoanilusa rof mom. ithW eht eWyaerb-ngdHir elrciip,nP uoy can griufe tou the brytaiipolb of eht oemthr ebign a :aercrir

q = ,4/s)rt000q(01 = 0210/

oS, qp2 = 2 * 1/002 * 021909/, ihcwh is ppoarx .1100/

oFr eth lhcid ot etg the elleal morf ,mom otw higtns deen to phnpea: )1( mmo stum eb a rrrciea y[otโ€œrezeho]gteโ€ and 2() mom muts spas eht llelea ot :idclh

  • tioybbPrial of mom gineb rcrreai = 010/1
  • tryabPobili fo mmo inpgass no sadseie leelal = 21/

ngtPiu it all ttogheer. Nwo, mibnoec lla gtoeet:hr

= a(typlobiibr of dda gebni crrreai) * rtyioblaib(p of dad spisnag on edssaie )lellae * yiltbpabio(r of omm gebni irrrc)ea * biabyorpt(il fo mom pgnsias on saseedi lla)lee

= /32 * 12/ * /0011 * /21
= 1 ni 060

kernicterusthefrog  oT oteuq hyTgor ,Thor darg e:equn ",we ,eJsus sgors" +52  
niboonsh  Thsi uienotsq amkse em awnt to ivotm +14  
drdoom  oll +  
5thgencephalosporin  ykoa wow +  
tekkenman101  You nac amek shti a olt rikcueq yb unsgi silpem urlse fro tlmouoaas evesseirc ssad) i.1see cefnadtfUe rptnea ihwt tcefdafe iegelna wlil eb a ceiarrr 32/ fo het ietm A()2 a) urfceeynq ni aitnpulpoo si upesr owl os yuo nca rgnoie P and jsut sue 2(q) ni doerr to aalucelct ierarrc qufcnree.y oS ktae the aersqu otor fo hte sooymgohuz eivseserc ueeycrnfq 10(0,)04/0 nda usjt lpgu ti in: )025(.0 = . 310) Teh dosd fo tiehr hidlc bengi dfefteca ithw teh two ptrsean gnbie dmauess lcihaotpyhte rsraiecr is 1/4 )a(a or aD.5d. 2s' aicrrre cncahe /)23( x M'oms reaircr acenhc ).(01 x hd'lcsi hecnac fo ngibe rsevecise .)2(5 +1  

Instead of doing all those calculations for the mom, you can also just multiply the dad's probability by 1/200 โ†’ q, the probability of the allele in the general population

+/- hungrybox(1263),

submitted by โˆ—keycompany(351),
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daiealnnM tsGn:eice

Mna has 23/ nchcae fo igebn a ir.rarce (eH dsoe otn vhea eth is) om nWa arrcier riks usmt eb cetdclaaul iwht p2^ + p2q + .q^2 ^q 2 = 140,/000 q = 0/1,02 p is hoyrlgu = p2q 1 = 1/100 = irrerCa nyeucerqf .

Riks of aihgvn a ihcld hstu uqaesl /23 x 0/101 x 4/1 = 160/0sc 2/3eB a:eu = Man rraCier isrk 0011/ = Famlee rCrarie k/s R41i = eacnCh tyhe hace sspa no het siesverec neeg ot hiret prof.sngfi

hello  See ym nlopnxtaaie fi uyo edne rmoe wrdos to xlipane itsh aploitenanx +2  

submitted by โˆ—hello(426),
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sThi eht amse as saeoycp'@yknm lannaetxoip wiht orem atxineaplon setho htat eend .i.t.

ehT taeintp si neetfdfacu yb eth raltrucapi tooalmasu rcsevesie assedie dna hsi ortrheb sha eth auoslaotm ciseveres sdesiae t;&g-- ihst smean ehac of rtieh tnrseap erirsca teh AR lelal.e ,Nwo orf eht tpaniet ot eb ftfanecude evgin tath obht his ranpets vahe hte RA laee,ll ti means ahtt eth etpitan sha a /23 ccenha taht he si iuytnsosalmule tudffacnee nad a .ricarre

heT ea'spintt npraret si tfcadefnue nda roanlm nyaeWedrrgiHb- estnicge a(s datest ni teh shit si cfailclyspie tnoe,ednim yuo ear to samuse tath teh aerprnt sah a arerric yueqenrfc rof het AR ale,lle whhci uealq ot pq2.

eTh daesesi hsa a fyrneucqe in teh poipaoltnu fo 0/0.1040 Tihs is q^2 -&-tg; 2q^ = /0.04010 ogSnvli for q, ouy tge q = /02.10

raCreir ufreycneq si .p2q eHweorv, rof a rrae sasedei, 2pq โ‰ˆ .2q o,S teh rcriera cfnqryeeu rof the rprtane = 2q = 2 * 0/012 = 100/1.

,woN teh Q sask oabtu an oprsngiff fo the peitnta adn ish enrtpar ngbei ecadefft, os ot heva na deftfeac idc,lh htere is a 14/ nacceh fo nvgaih na efectdfa ldcih (sceesabu het eatptni nda teh eaptrrn btho vaeh a 12/ nccahe fo sngsapi eth elalle -;-gt& oyu uiltlpme sheet hetetogr /12 * /1.2)

o,S imtluply 2/3 * 01/10 * 4/1 = 601/0. ihsT is ntetPip(a begni a )reircra * (rnratPpe geibn a ieacr)rr * vihP(nga na eeadctff ipofgfnsr teo)htreg.

submitted by beastfromtheastx(0),
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ehT ybibloratpi fo eht ahftre nigeb a areirrc si 2/3 nisec it is nwnok htat he otโ€™ndes hvae teh dsesaei. neTh eth blatrbyioip of imh pigssna ti on ot ihs idk si:

12/ * 3/2 = 13/

hWit teh digaHnryreeW-b Peirlcip,n you cna uifegr uto the liiborbtpya fo hte metohr gibne a rae:crri

q = 0(sqt01)0r,/04 = /1200

,oS 2qp = 2 * 102/0 * /990102, hhciw xpoapr is ,010/1 adn the bboairlytip of eht ilcdh ggitetn tish lellea is 001/1 * /12 = 00/21


0/120 * 1/3 = 061/0

brill45  You idd tish hgitr tub I hnitk eadm it a bti rmeo cietdpmlaoc atnh nedeed ot .be oT iuefrg out eth hkooildile fo a rnodam pnorse ni teh nualoptiop asnigsp no a escireesv lee,lal you tusj deen to od rqsuq)o2o(taer to gte ot q. nAd jstu use taht q to lytiumlp htwi eht 31/ uoy ogt eerai.rl The q aelvu elstl ouy hte alllee feyueqcnr in eth oapoilnput, ewehhtr het osenpr is a rcraeri or oozumsygho evcesresi tobh. oYu ltils gto ,it btu juts gleittn oyu nwko hte sraiee urtoe ni easc uoy ese it ania!g +2  

submitted by kdckjn(0),
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hwy etehr is loyprtaibbi of ratehf ibegn a rarirec is /23

drdoom  We uesmas iths is a versceise sseade.i nI eroth ,rwdso you nisametf eht eidesas if uoy rehiitn a issedae le,aell d, frmo your rmthoe adn a dseisae l,alele ,d fmro yoru e,ftrah ggnivi oyu an lelela iniprag tdoedne yb d.d dd = you eavh eht .ideasse heT etfhra does not vaeh teh eaesd;is sith esanm sih geetoypn acn nloy eb 1 fo ether :hsigtn ,DD ,Dd ro .Dd hTta is, DD = D mfro ish ad,d D omfr his o;mm dD = D mfor sih d,da d morf sih mo;m ro Dd = d omfr ish ,dda D from his Nociet htat ni only two fo etshe 3 silsiiobeipst sode het etrfah noaelyitpt()l hvae a saedeis elllae d)( taht he tigmh asps on to sih .npeoyrg +  

We assume this is a recessive disease. In other words, you manifest the disease if you inherit a disease allele, d, from your mother and a disease allele, d, from your father (giving you the allele pairing denoted by โ€œdd โ€).

dd = you have the disease.

The father does not have the disease; this means his genotype cannot be dd and thus must be one of 3 things: DD, Dd, or dD.

That is,

  • DD = D from his dad, D from his mom;
  • or Dd = D from his dad, d from his mom;
  • or dD = d from his dad, D from his mom.

Notice that in only two of these 3 possibilities (โ…”) does the father (potentially) have a disease allele, d, that he might pass on to his progeny.

+1/- drdoom(1181),

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