DNA and RNA
DNA and RNA are similar in a number of ways. Both of them are made up of pyrimidine and purine nitrogenous bases, a single radical of benzoic acid and a pentose molecule (Richards & Hawley, 2010). In both the DNA and RNA, the bases are connected in series in a backbone that holds them in place. During base pairing, both follows the same rules with the exemption being that RNA pairs the bases A and U. DNA and RNA are also different in some ways. DNA pairs the bases A with T, while RNA pairs A and U. Another visible difference is that RNA contains temporary information while DNA is a permanent record of genetic information. RNA is used to carry information to ribosome and eventually becomes degraded after it fulfills its function in the cells. Both have structural differences in that DNA mostly occurs as double stranded while the RNA contains single strands (Richards & Hawley, 2010).
Humans did not evolve with a centralized repository of DNA. As such, each cell in the human body contains its own DNA. This is because the cells of the human body are different and function entirely different. The DNA in each cell contains the blueprint which defines what the particular cell is, and its function in the body. This DNA directs the various activities of each cell in the body, directing it on the functions to do, the specific ways of carrying out the activities and when to carry out the activities. In other words, DNA directs specific divisions of single cells which make up the body. This formed the need for DNA which is different for each particular cell in the body, and thus the replication of DNA throughout the entire human body.
Richards, J. E., & Hawley, R. S. (2010). THE HUMAN GENOME: A User’s Guide. Burlington: Elsevier Science.