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NBME 21 Answers

nbme21/Block 4/Question#39 (52.1 difficulty score)
A 46-year-old man comes to the physician ...

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submitted by hello(349),
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2^q = 9001/ -t-&g; q = 103/

irrareC rfynqcuee per ebi-rWraedyngH mulrfao si .p2q

,wNo orf rrea aosloaumt resiceesv seasides het ecarrri yequrfenc of pq2 ≈ .2q

2q = 2(/103) = 03/2 = /511

esnwAr = /115

submitted by taway(32),
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sJtu sa a teno rfo yabydno lese who aws WTF at hwo 090/22(3(3/03)) = 1.5.a/1. tol fo ostnique bnask nrodu 2390/ ro( nay sliyrilam alreg o)nactirf tou to 1

gh889  I think you meant 2(29/30)(1/30) just to clarify! +7  
niboonsh  i am confusion +3  
arkmoses  You have to use the hardy weinberg formula (1=p^2+2qp+q^2)and p + q = 1 they basically tell you that q^2=1/900 which makes q=1/30 now you can figure out (p=1-q) so p=1-(1/30), p=29/30 then to figure out carrier you solve for 2qp, 2(29/30)(1/30)=1/15 I got it wrong cuz I forgot how to figure out p but hopefully wont happen on the real deal. +5  
garibay92  2pq= 2(29/30)(1/30).... Transform this to 2 1 1 2 1 x x = _ = ____ 1 1 30 30 15 +  
garibay92  Nevermind :/ It didn't come out as planned :( +  
garibay92  /Users/carlosgutierrez/Desktop/IMG_2423.jpg +  
pg32  How do we know this disease is autosomal recessive? I assumed it was just because they love these carrier frequency questions with AR diseases, but how do we know it's AR? +  
turtlepenlight  Sounds like Gaucher (ish?) if i'm remembering correctly +5  
ownersucks  Niemann Pick disease is characterized by foam cells, which are lipid-laden macrophages. Question stem also mention HSM +  

submitted by link981(172),
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^p2 + q2p + 2^q = =1 qp+ 1

=^q2 09=/01 q =p 1/03 /3092 hchiw drunso ot 1

ehTy ear kgnias orf irrcrea feeqrunyc ihwhc si .q2p

submitted by whoissaad(90),
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eWrhe is hsit eevn fmor? yM sni'md inggo hay iwre yngrti ot urnndsdeat .isth

sahusema  Hardy Wineberg equilibrium square root 900 = 30 1/2 of all offspring will be carriers so 30*.5 = 15 simple as that +6  
maxillarythirdmolar  this deserves a million upvotes. +1  

submitted by eacv(41),
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fI u ear tno otog in hmta liek me Dx. I ddi ti tish h:aywye T vgea em 00^1/9p2= os .03p/=1

Nwo I deen ot infd ,P so ues +p.= =pq1 3=1/-)(01 1=0.-03 7.09

,oS p2=q .)709(0.(023)= 4.600 = )(511/ D: I tgo it th,rig stih is my ywa ot do it sueac im not oodg ta toaisncfr.

eacv  **** q=1/900 +  
bdaines8  you literally have a calculator to use.... use it +  

submitted by electrosalt(0),

Here's how I did it

X is the frequency a parent will be a carrier of the disease. 1/4 is the probability the parents will have a child with the disease. Therefore

X * X * 1/4 = 1/900

X = 1/15