Transcription and Translation Notes (General Biology ), Study notes of Biology

Download Transcription and Translation Notes (General Biology ) and more Study notes Biology in PDF only on Docsity! Transcription and Translation Notes e Transcription: process by which mRNA is made from a gene’ s DNA sequence. mRNA stands for messenger RNA. occurs in the nucleus of eukaryotic cells (prokaryotes don’t have a nucleus so transcription and translation both take place in the cytoplasm) > > Translation: process by which a protein is made from an mRNA sequence. e So, transcription happens first, and is followed by translation. | remember this in two ways: first - the words definitions themselves help me out. To transcribe something means to make a copy of it. mRNA is a copy of a gene, whereas translating something means to convert it to a new language - in this case, to translate from the language of nucleic acids that use nucleotides into the language of proteins, which uses amino acids as its letters. The other way | remember that transcription comes first is that they both start with trans, but transcription has a “c” next, which comes before “!” in the alphabet! TRANSCRIPTION Each strand of DNA contains many genes. Transcription is making a copy of one of these genes that can then be used as the directions for the amino acid order in a protein. RNA Polymerase @ Molecular machine @ binds to the promotor region of a gene - this area becomes available for binding based on epigenetics. > There are thousands of proteins (called transcription factors) that either make it easier for RNA polymerase to bind, or those that inhibit its ability to bind this promoter (often by a process called methylation). This will ultimately determine when and how often this particular gene gets transcribed and is a vastly fascinating area of research right now. > Gene regulation manages which of these genes are expressed in any given cell in your body . e unwinds DNA @ adds RNA nucleotides to a template strand of DNA RNA uses uracil in place of thymine. > > RNAuses a ribose sugar in its backbone instead of the deoxyribose used in DNA. @ pre-mRNA has the potential to code for multiple proteins, depending on how it is edited. @ Once the RNA polymerase reaches the end of the gene, the sequence triggers release of the mRNA transcript. This sequence is composed of codons - three nucleotides that code for one of the 20 different kinds of amino acids. Genetic code - the amino acids that match with each code. e All mRNA transcripts start with the codon AUG that codes for the amino acid methionine. Processed mRNA transcripts leave the nucleus through nuclear pores TRANSLATION occurs in the cytoplasm on ribosome machines. Ribosome Composed of two pieces, or subunits @ mRNA transcript fits in between these pieces. @ mRNA is “read” one codon at a time. e@ Once the ribosome reads the codon, it is matched to the correct tRNA (or transfer RNA) anticodon. @ The anticodon must be complementary to the codon in order for the ribosome to let it bind. @ The ribosome continues adding amino acids to the chain until it reaches a stop codon. @ The stop codon causes the ribosome to release the tRNAs it is still holding, as well as the mRNA transcript. tRNA Each tRNA carries an amino acid. The tRNA that matches the AUG codon AL WAYS carries the amino acid methionine. Once a second correct tRNA is matched to the next codon, the ribosome forms a peptide link between the two amino acids. Now the amino acids are covalently bonded together . @ The ribosome can only work with two tRNAs at once, so the first one leaves its methionine behind and the empty tRNA is released. @ The released tRNA picks up another amino acid in the cytoplasm; in this case, it will pick up another methionine. @ The next codon is read, which tells the ribosome which tRNA to bring in, and then it covalently links the