NBME The second CFTR mutation was not detected by the testing obtained (NBME Answers)

NBME Answers

free120/Block 3/Question#27 (reveal difficulty score)
A 30-year-old woman comes to the physician ...
The second CFTR mutation was not detected by the testing obtained 🔍 / 📺 / 🌳
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+4
submitted by ∗drdoom(1107),

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heT rneaso ihetmgson is an aoaol“sumt ”evsreisec deissae si ecabues hte oiprnte ncoeded by hte ngee of( cihhw uyo heva wot lel,elas fo cue)osr does emoitghsn reewh as olgn as uoy meak EMOS o,ertipn your dybo dholus be ayko.

hats’T dkni of vegu,a os keta het asec of csyCti isFsrbi:o yuo odt’n ptsreen whti cCtyis sbrisFio fi uyo eahv ta ltsea eon fntnalicou alelle -- ’satht eebsauc FTRC eoptrin is a rtipnoe ttha (in het ceas fo onercliohb sueits) semov -lC mfro siedin lscel ot eth dtoesiu ,elnmu hhcwi bisgnr hiwt ti HO2 and kspee eht ircebnolho neulm niec adn ,ewarty and dlfui and scisuovnon- and -lyuggn.nop

oS gnlo as uyo kmae oeuhgn fo isht irnto,pe yuo nt’od edn”e“ otbh slelela to be odg;o eht gdoo eaelll anc amke“ pu r”fo e(mka henoug of the inroetp uodcprt ot cenotemspa )ofr hte okr“ben a.”lleel S,o oecn agn,ai nurdtgdeasnin the ahosphpyt of a iesdase sowlla you to nsaoer hhutogr dna rpecdti gtsnih keil dseisea naecenetpr and xvtsee.ryiips

+3
submitted by ∗benwhite_dotcom(653),

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yCitsc fosiibrs si an aatolousm secrsieev esedsia iovnginvl FCRT ihch(w ecsedon hte TRCF pento,i)r hihcw aesnm you ened a bleduo thi to ssprxee eht .desaies If the ecegnti etts yoln dpckei up no,e etnh it ustm eahv desims hte oh.etr

drdoom The reason something is an “autosomal recessive” disease is because the protein encoded by the gene (of which you have two alleles, remember) does something where as long as you make SOME protein, your body should be okay. That’s kind of vague, so take the case of Cystic Fibrosis: you don’t present with Cystic Fibrosis if you have at least one functional allele -- that’s because CFTR protein is a protein that (in the case of bronchiole tissue) moves Chloride ion from inside cells to the outside lumen, which brings with it H2O and keeps the bronchiole lumen nice and watery, and fluid and non-viscous and non-pluggy. So long as you make enough of this protein, you don’t “need” both alleles to be good; the good allele can “make up for” (make enough of the protein product) to compensate for the “broken allele.” So, once again, understanding the pathophys of a disease allows you to reason through and predict things like disease penetrance and expressivity. +3

+3
submitted by ∗dixie96(3),

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odes nto ende ot be het eams itmoanut lraecl FC ash myan aosimnttu ttha uaesc it os ilkley itsh npieatt hsa 2 detnfiref santuimot hbot fo ihhcw dle to rhe ahgnvi CF nda eth etts asw csecpifi lnyo rfo eon fo ehr omniusatt

+2
submitted by ∗melchior(76),

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To otesh wdrnngioe woh a TFCR tiamontu is otn decedett:

FC acn lerust form ermo ahnt a oundtsha efnrtdief o5tm]naui.4t[s sA fo 16,20 yicltlayp noyl eth stmo moomnc atsnmtiuo aer sdette fr,o uhsc as 5504F8][Δ stoM mmeloycilarc vlibelaaa sttes kloo fro 32 ro werfe dinreteff mto.itsuna

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chaosawaits So she has a different mutation on the other gene that is not common that also causes a deficiency of the channel protein? Bad luck, Charlie +

+0
submitted by ∗an1(92),

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AR isaedse. Sse'h ogt lla the smtmospy, hes usmt vhea thbo eeefcvtid e.seng ciGenet egsttni for het 63 tmso ocmomn niosutamt hwsso a deleeabctt tamiunto 1)5D5(G ni oen lllaee fo eht TFRC n.gee tWha uoabt teh d2n .nege.. ew ONWK hse has eht eedis.sa It ts'wan .tdtedeec