A panel consisting of 25 microsatellite markers was selected for the
diversity analysis of Tibetan sheep population. These were chosen from
literature related with sheep diversity studies aiming to analyze highly
polymorphic markers spread across the genome. These markers also
adhere to the guidelines of International Society for Animal Genetics
and FAO (http://dad.fao.org/en/refer/library/guidelin/marker.pdf).
Detailed information on primers is presented in Table 1. Forwardprimer
of each marker was 5′ labeled with fluorescent dye, i.e. FAM, NED, PET
and VIC. PCR amplification was performed in a reaction volume of
25 μl on i-cycler. Reaction mixture consisted of 50–100 ng of genomic
DNA, 200 μM of each dNTP, 50 pM of each primer and 0.5 units of Taq
DNA polymerase. The amplification was carried out using a Touchdown
program for all microsatellite loci, which consists of initial denaturation
of 95 °C for 1min; 3 cycles of 95 °C for 45 s and 60 °C for 1 min, 3 cycle of
95 °C for 45 s and 57 °C for 1 min; 3 cycles of 95 °C for 45 s and 54 °C for
1 min, 3 cycles of 95 °C for 45 s and 51 °C for 1 min and 20 cycles of 95 °C
for 45 s and 48 °C for 1 min. The PCR amplification was confirmed by
electrophoresing the products in 1.8% agarose gel followed by staining
with ethidium bromide (0.5 mg/ml). PCR products were multiplexed
(Table 1) and genotyping was carried out on an automated ABI-3100
DNA sequencer (Applied Biosystems, USA) using LIZ 500 as the
internal size standard (Applied Biosystems, USA). Allele sizing was
done using GeneMapper™ software v 3.7. Stutter related scoring
error, often seen in dinucleotide repeats, was absent and alleles could
be scored unambiguously.