DNA application under synthesis

DNA application under synthesis

The synthesis or the S phase of cell cycle is when the DNA of each chromosome is copied. This process is known as DNA replication. Each chromosome consists of many genes that hold the genetic information that is transferred. Indeed, it is the combination of a genetic organization that determines all of its characters. It codes for the manufacture of peptides, which themselves are composed of amino acids. DNA is a sequence of nucleotides and a protein molecule is a sequence of amino acids. A gene is a particular sequence of nucleotides within the DNA that specifies the sequence of amino acids in a particular protein. By controlling which proteins are produced by an individual cell the gene controls the characteristics of that cell and, consequently, the characteristics of tissues, organs, and organisms. Proteins, and consequently genes, vary in length, but most genes are approximately 1,000 to 4,000 nucleotides long. The entire complement of genes in an organism's DNA is called the genome (James, 2001).

A gene is a DNA fragment, which is in the nucleus. It consists of a sequence of nucleotides (variable number may range, for example up to several thousands), and allows the synthesis of a protein, process which occurs in the cytoplasm. The DNA synthesis takes place in two parts (Arthur and Tania, 2005).

The transcript

The translation

The Transcript

At the level of transcription, the double helix of DNA opens by an enzymatic complex (group of enzymes), RNA polymerase progresses along the DNA and catalyzes the formation of a messenger RNA from a matrix (the transcribed strand) on the basis of the complementary bases.

RNA messenger is identical to the coding strand, only the thymine (T) which is replaced by uracil (U). Once past the RNA polymerase, the double helix of DNA is reformed. When the transcription termination signal is emitted, DNA polymerase, DNA, and RNA messanger gets separated. Many RNA polymerases travel along a gene (Arsceni, 2005).

The Translation

The translation involves ribosomes that consist of ribosomal proteins and RNA and transfer RNA (tRNA), intermediate between the codon and amino acid. Enzymes catalyze the synthesis of the polypeptide. Ribosomes are bodies involved in this translation: they build the polypeptide by the gradual establishment of a sequence of amino acids according to the codons of mRNA.

There are 3 steps in translation (Arthur and Tania, 2005):

Initiation: begins with setting of a ribosome on the AUG codon corresponding to the methionine (start codon). The amino acid chain builds with a methionine (eliminated at the end of translation which counted as No. 0) (Hugh, 2007). The elongation of the polypeptide: another t-RNA (with a corresponding amino acid methionine at following codon) binds to the site of the ribosome. An enzyme connects the two amino acids by a peptide bond. Then shifts the ribosome to mRNA and the codon following the second tRNA is found on the P site, thus freeing the A site to allow the fixing of a new tRNA r (corresponding to the third codon) and then carrying ...