The functional products of most known genes are proteins, or, more accurately, polypeptides. Polypeptide is just another word for a chain of amino acids. Although many proteins consist of a single polypeptide, some are made up of multiple polypeptides.
Genes that specify polypeptides are called protein-coding genes. during expression of a protein-coding gene, information flows from DNA → RNA → protein. This directional flow of information is known as the central dogma of molecular biology.
Non-protein-coding genes (genes that specify functional RNAs) are still transcribed to produce an RNA, but this RNA is not translated into a polypeptide. For either type of gene, the process of going from DNA to a functional product is known as gene expression.
Transcription
• Transcription is the first step in gene expression. It involves copying a gene's DNA sequence to make an RNA molecule.
• Transcription is performed by enzymes called RNA polymerases, which link nucleotides to form an RNA strand (using a DNA strand as a template).
• Transcription has three stages: initiation, elongation, and termination.
• In eukaryotes, RNA molecules must be processed after transcription: they are spliced and have a 5' cap and poly-A tail put on their ends. Transcription initiation To begin transcribing a gene, RNA polymerase binds to the DNA of the gene at a region called the promoter.
Basically, the promoter tells the polymerase where to "sit down" on the DNA and begin transcribing. Elongation Once RNA polymerase is in position at the promoter, the next step of transcription-elongation-can begin. Transcription termination RNA polymerase will keep transcribing until it gets signals to stop. The process of ending transcription is called termination, and it happens once the polymerase transcribes a sequence of DNA known as a terminator. #ProcessOfTranscription #CentralDogmaForGeneExpression #DNATomRNA
10 окт 2024
