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LIFE09200604007 Tabish - Homi Bhabha National Institute

LIFE09200604007 Tabish - Homi Bhabha National Institute

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Synopsis<br />

8.3 Restriction fragment length polymorphism (RFLP): Restriction digestion of the<br />

PCR product with appropriate restriction enzyme was done to analyse the genotype.<br />

PCR product from gene specific PCR reactions was incubated with specific restriction<br />

enzyme with appropriate buffer. Restriction digestion products were analysed by<br />

agarose gel electrophoresis along with DNA ladder.<br />

8.4 SNaPshot reaction: SNaPshot genotyping is based on the dideoxy single-base<br />

extension of an unlabeled oligonucleotide primer which binds to a complementary<br />

template in the presence of fluorescently labelled ddNTPs and Taq DNA polymerase.<br />

The polymerase extends the primer by just one nucleotide, adding a single ddNTP to its<br />

3‟ end. First the desired gene was amplified by PCR using gene specific primers.<br />

SNaPshot assay was performed according to manufacturer‟s protocol which consists of<br />

three steps: (1) EXO-SAP purification (remove unused dNTPs, primer and primerdimers),<br />

(2) SNaPshot reaction (single base extension of the primer) and (3) Post<br />

SNaPshot purification (remove unused ddNTPs from SNaPshot reaction. The processed<br />

samples were then sequenced in Genetic analyzer for interpretation of SNaPshot<br />

results.<br />

8.5 Genotype Score: Genotyping of 22 candidate single nucleotide polymorphisms<br />

(SNPs) in 17 candidate genes involved in DNA repair, apoptosis, cell cycle regulation<br />

and carcinogen metabolism was done and a Genotype Score (G Score) was created<br />

from the number of variant alleles. A value of 2, 1 and 0 was allotted to homozygous<br />

variant, heterozygous and homozygous wild type alleles respectively, and a<br />

consolidated G Score was calculated taking values of all genes together.<br />

9. Microarray: Whole genome expression profiling was done for 5 MPN and 5 Control<br />

cell lines after 5 Gy γ-radiation exposure and 24 h time point using Toronto 27 K slides<br />

(University Health Network Microarray Centre, Toronto). RNA was isolated using<br />

TRIzol protocol and was used for first strand cDNA synthesis using Superscript II<br />

reverse transcriptase for each slide. Indirect labelling of test and reference cDNA<br />

samples was done using Cy5 and Cy3 dyes (Amersham), respectively. Labelled<br />

samples were added to microarray slides and were kept in hybridization chambers at 42<br />

o C in water bath overnight. After hybridization slides were sequentially washed using<br />

reducing concentrations of saline sodium-citrate (SSC) buffer containing SDS. The<br />

9

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