Ans. is 'c' i.e., Tay-Sach's disease Ion channels provide pores for the passive diffusion of ions across biological membranes.They are often highly selective for a particular ionic species, leading to a classification into sodium (Na+), potassium (K+), calcium (Ca2+), chloride (Cl)and unspecific cation channels. Ion channels serve many functions apart from electrical signal transduction: chem ical signalling (Ca2+as a second messenger), transepithelial transport, regulation of cytoplasmic or vesicular ion concentration and pH, and regulation of cell volume. Therefore, ion channel dysfunction can cause diseases in many tissues.The list of human diseases known to be associated with defects in ion channels has grown considerably during the past years. This review gives a short overview of known channelopathies, and focuses in particular on recent findings and on channelopathies that have significantly advanced our physiological insight.Known ion channel diseasesChannelGene |DiseaseCation channels:CHRNA1 /ACHRACHRNA1* Myasthenia congenitaCHRNA4CHRNA4* Autosomal dominant nocturnal frontal lobe epilepsyCHRNB2CHRNB2* Autosomal dominant nocturnal frontal lobe epilepsyPolycystin-2PKD2* Autosomal dominant polycystic kidney disease (ADPKD)CNGA3CNGA3* Achromatopsia 2 (color blindness)CNGB1CNGB1* Autosomal recessive retinitis pigmentosaCNGB3CNGB3* Achromatopsia 3Sodium channels:Navl.lSCN1A* Generalized epilepsy with febrile seizures (GEFSp))Navl.2SCN2A* Generalized epilepsy with febrile and afebrile seizuresNavl.4 paralysisQSCN4A* Paramyotonia congenitaQ potassium aggressive myotonia, hyperkalemic periodicNavl.5SCN5A* Long-QT syndrome, progressive familial heart block type I, Brugada syndrome (idiopathic ventricular arrhythmia)SCN1BSCN1B* Generalized epilepsy with febrile seizures (GEFSp))ENaCaSCNN1A* Pseudohypoaldosteronism type 1 (PHA1)ENaCbSCNN1B* PHAI, Liddle syndrome'2 (dominant hypertension)ENaCgSCNN1G* PHAI, Liddle syndromeQPotassium channels:Kvl.lKCNA1* Episodic ataxia with myokymiaKCNQl/KvLQTlKCNQ1Autosomal dominant long-QT syndrome (Romano-Ward)Autosomal recessive long-QT syndrome with deafness (Jervell-Lange-Nielsen)KCNQ2KCNQ2* BFNC (epilepsy), also with myokymiaKCNQ3KCNQ3* BFNC (epilepsy)KCNQ4KCNQ4* DFNA2 (dominant hearing loss)HERG/KCNH2KCNH2* Long-QT syndromeKirl.l/ROMKKCNJ1* Bartter syndromeQ (renal salt loss, hypokalemic alkalosis)Kir2.1/IRK/KCNJ2KCNJ2* Long-QT syndrome with dysmorphic features (Andersen syndrome)Kir6.2/KATpKCNJ11* Persistent hyperinsulinemic hypoglycemia of infancy (PHHI)SUR1SUR1* PHHIKCNE1 /MinK/ISKKCNE1* Autosomal dominant long-QT syndrome (Romano-Ward) Autosomal recessive long-QT syndrome with deafness (Jervell-Lange-Nielsen)KCNE2/MiRPlKCNE2* Long-QT syndromeKCNE3/MiRP2KCNE3* Periodic paralysisCalcium channels:Cavl.lCACNA1S* Hypokalemic periodic paralysisQ, malignant hyperthermiaCavl.4CACNA1F* X-linked congenital stationary night blindnessCav2.1CACNA1A* Familial hemiplegic migraineQ, episodic ataxiaQ, spinocerebellar ataxia type 6QRyRlRYR1* Malignant hyperthermia, central core diseaseRyR2RYR2Catecholaminergic polymorphic ventricular tachycardia, arrhythmogenic right ventricular dysplasia type 2 Chloride channels:CFTRABCC7* Cystic fibrosisQ, congenital bilateral aplasia of vas deferensClC-1 CLCNl* Autosomal recessive (Becker) orC1C-5 CLCN5dominant (Thomsen) myotonia * Dent's diseaseQ (X-linkedC1C-7 CLCN7proteinuria and kidney stones) * Osteopetrosis (recessive orCIC-Kbdominant)CLCNKB* Bartter syndromeQ type IIIBarttin BSNDBartter syndrome typeQ IVGLRA1 (associated with sensorineural deafness)GLRA1 * Hyperekplexia (startle disease)GABAal GABRA1* Juvenile myoclonus epilepsyQGABAg2 GABRG2* EpilepsyGap junction channels:Cx26GJB2* DFNA3 (autosomal dominantCx30 GJB4hearing loss)DFNB1 (autosomal recessive hearing loss)DFNA3Cx31 GJB3* DFNA2Cx32 GJB1* CMTX (X-linked Charcot- Marie-Tooth neuropathy)