Dominance/Recessive: If your genotyping method allows you to observe both alleles (you see both the C and T allele if the individual is truly CT) then the marker is codominant (neither dominant or recessive).

For your population, you only see T alleles, so the allele frequency (of the reference allele) is zero and Hardy-Weinberg is not relevant as there is no variation in your population.

Thank you Ali Mahmoudpour and Ken G Dodds for your answer.

I am elaborating details of my work below. Pls guide on us.

I have screened one human gene for polymorphism (SNP) as per findings seen in vitro study model to check in ex-vivo by Sanger sequencing method. Data was analysed SeqScape software, in that reference sequence taken form UCSC browser. When data of all samples compaired with reference sequence that time i observed, in reference sequence 'C' nucleotide and all samples sequence having 'T' nucleotide. Although it is synonymous change but this has been done first time in this groups and population. 

Considering above all i didnt understand what kind of polymorphism it is? may i think about dominance /recessive genotype? can i calculate frequency? 

Please guide on us.

Dear Nawaj

When we talk about one locus and talking about dominance and recessive, then we must use the same letter C or T and use the capital letter for the dominance allele and small letter for the recessive allele.

Calculating gene frequency for dominant allele can be achieved by square root of the genotypic frequency of the recessive to get ( q ), then calculate the dominant allele frequency ( p ) from the equation p+ q = 1

Good Luck

 Thank you all.