Protien Synthesis

Protein Synthesis

The Expression of a Gene

The process of Protein Synthesis involves many parts of the cell. Unlike other similar productions, this process is very complex and precise and therefore must be done in proper sequence to work effectively. The slightest error during this process could cause the action to experience difficulty or even fail. For example, in the production of starch, glucose molecules are combined to be stored and eventually utilized as usable chemical energy. The cell can break down the starch with little difficulty as if each molecule was identical, even though there is a wide variety of molecules. This is a different case in Protein Synthesis. In Protein Synthesis, there are twenty different amino acids and if one is out of place than is will effect the specificity of the protein. In a healthy person, the protein hemoglobin can be found in red blood cells, hemoglobin is helps with the transfer of respiratory gases from the blood to the tissues of the body. With an illness called sickle-cell anemia, the red blood cells are changed from a round, disk shape to a floppy looking sickle shape. These cells therefore cannot pass through small blood vessels due to their divergent shape. The actual cause of this mutation is a gene disorder, where the sixth codon of the protein glutamaric acid is changed with valine. This small change in the genetic code can cause severe defects in the effected such as blood clots, severe disorders and even death. All this can result from a misinterpretation in one codon in a chain of hundreds! Protein synthesis acts in this way, that is if there is only the most minuscule mistake it can have monstrous effects.

THE BASICS OF DNA AND GENES

Protein synthesis first begins in a gene. A gene is a section of chromosome compound of deoxyribonucleic acid or DNA. Each DNA strand is composed of phosphate, the five-carbon sugar deoxyribose and nitrogenous bases or nucleotides. There are four types of nitrogenous bases in DNA. They are (A)denine, (G)uanine, (T)hymine, (C)ytosine and they must be paired very specifically. Only Adenine with Thymine (A-T) and Guanine with Cytosine (G-C).

To form a polynucleotide DNA, many nucleotides are linked together with 3'-5' phosphodiester linkages. In a complete molecule of DNA two of these polynucleotide strands are linked together by nitrogenous bases at 90 degrees to the sugar-phosphate "spine" (FIG. 1). The nitrogenous bases are held together with weak hydrogen bonds. One polynitrogenous chain runs in a 3'-5' direction, the 3' being the top hydroxyl and the 5' being the bottom phosphate attached to the carbon five of the sugar. The other string runs the opposite. The two strands of the structure cannot be identical but they are complimentary. There is no restrictions on the placement and sequence of the nucleotides, which becomes important in storage of information.

TRANSCRIPTION: The Synthesis of RNA

Genetic information would be rendered useless if the stored information did not have a way of reaching the desired focal area. Since protein synthesis occurs in the cytoplasm and the DNA must remain in the nucleus, a way of transporting the code is essential. This comes in the form of messenger ribonucleic acid or m-RNA. Since the information on the DNA must stay the same on the m-RNA, the two have to be very similar. There are three major differences between RNA and DNA. RNA is only a single strand. The five carbon sugar of RNA is ribose opposed to deoxyribose and in RNA the pyrimidine uracil (U) replaces DNA's pyrimidine thymine (T). Since RNA is produced from DNA, the nucleotides of RNA can hold the same information as the nucleotides of DNA because the code for amino acids is centered around the RNA structure.

The process in which m-RNA is synthesized is called transcription. This process is similar to DNA replication in the way that for transcription to occur, the double helix DNA must be unwound as in DNA replication (FIG 2). The major difference between transcription and replication is that in transcription only one of the strands is used as a template and only one m-RNA strand is produced. Transcription can be broken up into three parts in order to be understood. These steps are: i)initiation, ii)elongation and iii)termination. Initiation of transcription is how the transcription begins. The enzyme responsible for m-RNA synthesis is called RNA polymerase 2. The RNA polymerase knows where to begin transcription because it is coded into the DNA.

Elongation of transcription represents how the process happens.