We have made a density functional study of the structural and electronic properties of B or N (individual) doped and BN co-doped graphene. The effect of doping has been studied by incorporating the doping concentration amount varying from 2% (one atom of the dopant in 50 host atoms) to 12 % atomic concentration in case of individual doping and from 4% (2 atoms of the dopant in 50 host atoms) to 24 % in case of co-doping, at the same time, altering different doping sites for the same concentration of substitutional doping. We made use of VASP (Vienna Ab-Initio Simulation Package) software based on density functional theory to perform all calculations. While the resulting geometries do not show much of distortion on doping, the electronic properties show a transition from semimetal to semiconductor with increasing number of dopants. The study shows that the BN doping introduces the band gap at the Fermi level unlike individual B and N doping which causes the shifting of Fermi level above or below the Dirac point. It is observed that not only concentration but position of B and N atoms in the hetero-structure also affects the value of band gap introduced.