Representative electrophoresis of the PCR products of 24 bp indel in the promoter region of the prolactin gene on 2% agarose gel. M: DNA ladder (50 bp). No. 1-4; 7-8 and 11: individual samples with DD genotype; Nos. 5-6 and 10: ID genotype; No. 9: II genotype; (-): Negative control.