Chromatogram is really important when you have to read a sequence. Often if you read only FASTA file, you can lose some variations that you can see only watching the chromatogram, especially when you have a missense mutation, because the double peak that you have in the chromatogram is difficult to be detected if you have only a FASTA file

Another issue that is important when reading Sanger sequencing data is the peak resolution. Peak resolution is limited to the quality of the template, the primer and the type of instrument used. Peak resolution can often begin to degrade as early as 600 bases downstream from the primer for older systems and often lead to calling multiple bases for a single peak. Sequencing analysis programs will often provide sequence data beyond the point where resolution is degrading. We have seen problems in primer walking a gene when people use only FASTA or text files to select a primer and the primer doesn't work simply because the text data is not accurate. When we select a primer from sequence data, we always use the chromatogram to view peak resolution.

As Pia suggested, there are freeware programs that will allow you to view the electropherogram provided by Geospiza and ABI which work with MAC and Windows compatible systems.

I am assuming you have sequence data generated by a machine, in that case you need the original chromatogram files that were output by the machine and which can not be altered. Without them your sequence is not verifiable.

Thanks for the response sir one of my research colleague is having 16s rRna sequencing data and he has obtained accession number by submitting the sequences to NCBI Gen bank he is not having the chromatogram does it possible to obtain chromatogram ?