Extended optimization studies were performed to maximize PCR
amplification efficiency of GC-rich 1087 bp fragments for both HBA1
and HBA2 genes, including Mg2+ and DMSO concentration, enzyme
units, primer concentration and PCR cycling parameters. In addition,
several parameters affecting the specificity and the yield of genotyping
reaction were optimized. These includeMg2+ concentration, annealing
temperature and time, concentration of primers and dNTPs, quantity of
DNA template, etc. The effect of each parameter was studied in a series
of PEXT reactions containing amplified target DNA from wild type
samples or samples carrying mutations and varying amounts of the parameter
under investigation. Some indicative results of the performed
optimization studies are presented in Fig. 2. The optimized parameters
selected for the multiplex PEXT reactions were as follows: Mg2+ concentration
4 mM, allele-specific primer concentration 1 pmol each,
annealing temperature 65 °C (60 °C for HBA2 gene), dNTPs concentration
10 μΜ and about 100 fmol (2 to 3 μL) of unpurified PCR product.