Deoxyribonucleic acid, DNA, is involved in the manufacturing process of all proteins in the body. It synthesizes proteins that repair and replace worn out tissues in the body. Stem cells (undifferentiated cells with the ability to differentiate) researches have shown that cells from some regions of the body can differentiate into different tissues. Therefore, they can replace worn out tissues and hence function as a repair mechanism. These cells can be induced to become tissue or organ cells. Scientists argue that perhaps the stem cells may carry out similar functions as DNA hence can replace it. This paper seeks to show that the DNA plays a key role in all the processes that take place in and outside the cell.
Before cell division, the genetic materials and other organelles in the cell must double up such that the new cell can also have the right quantities of these elements. Therefore, DNA must create an exact copy of itself in a process called replication. During the replication, an enzyme called DNA polymerase first unzips the two strands of the DNA, and a replication fork is formed. Helicase enzyme then unwinds the double helix at the replication fork to set two parent strands which act as templates. Primase then produces RNA primer at the 5’ end and also at the Okazaki fragments (these are fragments of DNA that are formed in the process). DNA polymerase III then catalyses the synthesis of new strands from the 5’ to the 3’ end direction.
The formation of the two strands occurs at different rates. DNA ligase then joins the Okazaki segments on the lagging strand. Finally, DNA polymerase proofreads the new strand to ensure that correct nucleotides have been added (Lewin, 2000). See figures 1 and 2 for illustrations.
DNA contains genes that are codes for the synthesis of various proteins in an organism. The codes must be translated so that the protein they code for can be synthesized. Before protein synthesis occurs, transcription of the DNA into a messenger RNA takes place. The messenger RNA is then translated (Griffiths, 2005). The process of transcription begins in the 5’ end and is initiated by RNA polymerase II using a DNA strand as a template. It begins at the promoter sequence on the template strand and ends at the terminator sequence. RNA polymerase attaches to the DNA and unwinds the helix hence leading to the formation of new nucleotides along the template strand. Once it is through, RNA polymerase then zips back the opened strands. The new strand formed is called mRNA (Cox et al., 2005).
The mRNA formed moves to the cytoplasm of the cell where it binds to a site on a ribosome where it is translated to produce a protein. Transfer RNA translates the message in the nucleotide sequence of the mRNA into amino acids. The tRNA contains an anticodon that recognizes the sequences (codons) in the mRNA. The mRNA and the tRNA then both bind to the ribosome at different sites. The ribosome moves along the mRNA during the formation of the amino acids. When it reaches a different codon, a tRNA with that anticodon comes in until the termination codon is reached. The chain of amino acids formed are joined together to form a polypeptide chain that is modified to form a protein (Pique-Regi et al., 2011; Lehninger, 2005). See figures 3 and 4 for illustrations.
The death cap mushroom (Amanita phalloides) is one of the most poisonous fungi existing. It contains two main toxins called amatoxins and phallotoxins that affect the kidney. The toxins exhibit severe effects that can cause death when ingested. They also prevent RNA polymerase II from forming mRNA hence making it impossible to generate a template that guides the process of protein synthesis. Therefore, the required proteins for cell division are not formed leading to the inability of the cell to carry out its normal functions. For instance, no new cells can be synthesized thus leading to death (Hanson, 2008).
References:
Griffiths, A. J. F. (2005). Introduction to genetic analysis. New York: W.H. Freeman and Co.
Hanson, J. (2008).The chemistry of fungi, RSC Publishing, Cambridge,
Lehninger, A. L., Nelson, D. L., & Cox, M. M. (2005). Lehninger principles of biochemistry. New York: W.H. Freeman.
Lewin, B. (2000). Genes VII. New York: Oxford University Press.Top of Form
Pique-Regi, R., Degner, J. F., Pai, A. A., Gaffney, D. J., Gilad, Y., & Pritchard, J. K. (January 01, 2011). Accurate inference of transcription factor binding from DNA sequence and chromatin accessibility data. Genome Research, 21, 3, 447-55.Top of Form
