You have sequenced the genome of the bacterium Salmonella ty

You have sequenced the genome of the bacterium Salmonella typhimurium and find a protein that is 100% identical to a protein in the bacterium Escherichia coli. When you compare the sequences of the S. typhimurium and E. coli genes, however, you find that their DNA sequences are only 87% identical. Explain this observation-how could identical proteins be encoded by different DNA?

Solution

In general, the different cell types contain the same DNA, it is the proteins that is being translated from RNA which is transcribed from DNA that results into different cells performing different functions. Here, its a little different. S.typhimurium DNA-B is a member of the protein family whose prototype is the E.Coli DNA-B protein, the very typical DNA binding protein OmpR is identical between these two organisms, and the widely conserved fab gene cluster are the primary reasons for such an effect.

References

1. Wong, A., Kean, L., & Maurer, R. (1988). Sequence of the dnaB Gene of Salmonella typhimurium. Journal of bacteriology, 170(6), 2668-2675.

2. Quinn, H,J., Cameron, A,D,S., & Dorman, C,J. (2014). Bacterial Regulon Evolution: Distinct Responses and Roles for the Identical OmpR Proteins of Salmonella Typhimurium and Escherichia coli in the Acid Stress Response. PLOS genetics.

3. Zhang, Y., & Cronan, J, E, Jr. (1998). Transcriptional Analysis of Essential Genes of the Escherichia coli Fatty Acid Biosynthesis Gene Cluster by Functional Replacement with the Analogous Salmonella typhimurium Gene Cluster. Journal of bacteriology, 180(13), 3295-3303.