User:Amare ayalew/sandbox

RNA and Gene Transcription ￼￼￼￼TRANSCRIPTION • Transcription is the process of RNA synthesis from a DNA template • In genetics, the term refers to the copying of a DNA sequence into an RNA sequence i.e Transcription is the DNA-directed synthesis of RNA • The synthesis of an RNA molecule from DNA is a complex process involving DNA-dependent RNA polymerase enzymes and a number of associated proteins (transcription factors). – DNA base sequences define the beginning and end of a gene and regulate the level of RNA synthesis – Then proteins must recognize and act on DNA for transcription to occur                                                                                                                                   RNA: Types & structures • RNA, like DNA, is a long, unbranched polymer consisting of ribonucleotides joined by 3’-5' phosphodiester bond as in the case of DNA. • There are different types of RNA Transfer RNA (tRNA) Ribosomal RNA (rRNA) Messenger RNA (mRNA) small nuclear RNA (snRNA) micro & silencing RNAs Messenger RNA • The most heterogeneous in abundance, size and stability • Functions as a messenger conveying the information in a gene to the protein- synthesizing machinery. • Each mRNA serves as a template on which a specific sequence of amino acids is polymerized to form a specific protein molecule • It carries the transcript of the nucleotide sequences corresponding to the sequence of amino acids in the protein they code for.Transfer RNA • tRNA is the simplest and smallest tRNA(74-95 nt) • serve as adapters for the translation of the information in the sequence of nucleotides of the mRNA into specific amino acids. • The structure of tRNA is characterized by the presence of several intra-chain hydrogen bonds that give it a clover-leaf like shape.