TRANSCRIPTION OF DNA AND TRANSLATION OF RNA Student researchers: Lolita MONNIER ; Christine LAM ; Thibault MARTIN-LAGARDETTE School address : Lycée Romain Rolland 17, rue Lucien Nadaire 94200 Ivry / Seine Grade : 2nde (section européenne) Teachers : Martine PERNODET ; Nathalie OCTO 1°) Statement of purpose and hypothesis We learned that the DNA (deoxyribonucleic acid) carries the genetic message of an individual. So the DNA is the support of the genetic information. It is located in the nucleus of eukaryote cells and in the cytoplasm of the prokaryote cells. DNA is a double helix composed of two chains of nucleotides rolled up one around the other one. These chains contain a deoxyribose and a phosphate associated to a nitrogenous base (adenine, guanine, cytosine and thymine). Hydrogen bands situated between the nitrogenous bases connect both chains. The proteins carry out information. So we want to explain the link between DNA and the proteins, consequently, the link between DNA and the features of the organism. So, we want to know what the link between DNA and the features of organism are; that is to say how DNA encodes information. We suppose that RNA is this link between DNA and proteins. 2) Methodology To test our hypothesis, we were in quest of information about transcription of DNA and about the translation of the RNA. That’s why we read few scientific articles on Internet (www.mit.edu:8001/esgbio/dogma; www.brooklyn.cuny.edu/bc/ahp/BioInfo www.blc.arizona.edu/Molecular_Graphics/DNA_Structure/DNA_Tutorial.HTML ). After that, we worked on a biology school-book (sciences et vie de la Terre 1re S R. TAVERNIER et C. LIZEAUX). As a result we made a model of the transcription of a DNA sequence. Moreover, we realized the translation of our RNA molecule thanks to an informatics program. 3) Analysis of data The genes are located in the nucleus while their expression takes place in the cytoplasm. That is the reason why they need an intermediary or a messenger. A copy of the gene (DNA) in the form of RNA is thus necessary, it is realized during the transcription process. The zone of synthesis moves along a DNA. strand. First of all, an enzyme called the polymerase RNA unwinds DNA’s helix and breaks the bands between the bases pairs. Then, a copy of DNA’s message is created: messenger the RNA is synthesized. The nucleotides of thymine (T) are replaced by uracile (U) in the RNA molecule and it will allow the transfer of the genetic information through the nucleus membrane towards the cytoplasm. The RNA is very similar to a DNA stand: it is composed of a chain of nucleotides containing a ribose (instead of a deoxyribose in DNA and a base [adenine guanine, cytosine, and uracile instead thymine in DNA ] ). The second stage of gene expression is the translation. In a bacteria, DNA, mRNA and ribosomes are the same cellular compartment. In eukariotic cells, RNA goes in the cytoplasm in order to be translated by the ribosome. A ribosome is an organelle, which allows the synthesis of proteins. The genetic translation of the information begins with the association between the mRNA and a ribosome at an initiating triplet (the three nucleotides AUG) of the mRNA molecule. Each ribosome covers two triplet of mRNA and set up two molecules of transfer RNA (tRNA) with their respective amino acid. During the progression oh the ribosomes, amino acids are added to the peptide chain. This operation is repeated at each new triplet of the mRNA. Finally, the polypeptide chain is released after the ribosome has met a stop triplet. 4) Summary and conclusion During the process of the transcription are involved in the translation, the genetic information is transformed to produce proteins. This DNA’s translation allows the genetic information to be amplified. For each gene, a lot of copies of mRNA are produced. Each mRNA is translated many times, some a huge member of the protein is produced. Thus, DNA is protected in the nucleus. 5)Vocabulary Amino acid : Basic unity of proteins. There are 20 kind of amino acid in the nature Cytoplasm: The substance contained within the plasma membrane of the cell. The region in which translation takes place. Gene: An inherited set of instructions for making proteins. mRNA: (Messenger RNA). A type of RNA, which transports the information about the sequence of the amino acids in the protein to be manufactured, from the nucleus to the ribosomes. Ribosome: A cellular component composed of proteins and another class of RNA (rRNA). tRNA: (Transfer RNA). tRNA binds to a specific amino acid and has an anticodon on one end. The anticodon bears a set of three bases, which are complementary to the mRNA cordon for that particular amino acid. It carries its amino acid to a ribosome during protein synthesis.