My AP Biology Thoughts Unit 6 Gene Expression and RegulationWelcome to My AP Biology Thoughts podcast, my name is Saarim Rizavi and I am your host for episode #108 called Unit 6 Gene Expression and Regulation: Translation. Today we will be discussing everything there is to know about translation. I will first be giving a brief overview of what translation is, it’s overall function, the 3 steps involved in translation, and some of the different components and organelles involved in translation. I’ll then go into greater detail on the individual steps of translation which will involve the organelles and different components mentioned before. Finally, I will relate the process of translation to the broader topic of gene expression and regulation. Before I begin, I would like to give credit to Khan Academy, biologydictionary.com, and nature.com for the information they provided me with in order for this podcast to be possible. So thanks to them. Alright, so here we go: Segment 1: Introduction to TranslationTranslation is the process of creating proteins from an mRNA template A cell reads information from mRNA molecules and uses this information to build a protein - involves decoding an mRNA and using its information to build a polypeptide, and multiple polypeptide chains form a protein Three basic steps of translation - initiation, elongation, and termination Initiation - the ribosomes get together with the mRNA and the first tRNA so translation can begin Elongation - the amino acids are brought to the ribosome by tRNAs and linked together to form a chain of amino acids Termination - the finished polypeptide is released to go and do its job in the cell In mRNA, the instructions for building a polypeptide come in groups of 3 nucleotides called codons - there are 61 codons for amino acids and each of them is read to specify a certain amino acid out of the 20 possible amino acids Stop codons tell the cell when polypeptide is complete and the AUG codon is the start codon which signals the start of protein construction In translation, the codons of an mRNA are read in order, from the 5’ end to the 3’ end, by tRNAs. tRNA’s = molecular bridges that connect mRNA codons to the amino acid they encode One end of the tRNA has a sequence of 3 nucleotides called an anticodon, which binds to a matching mRNA codon through base pairing; the other end of the tRNA carries the amino acid specified by the codons tRNAs bind to mRNAs inside the ribosomes - ribosomes are made up of protein and ribosomal RNA The ribosomes provide a set of slots where tRNAs can find their matching codons on the mRNA template and deliver their amino acids. As these tRNAs enter slots in the ribosome and bind to codons, their amino acids are linked to the growing polypeptide chain in a chemical reaction. Segment 2: More About Translation Initiation Ribosome, an mRNA with instructions for the protein to be built, and an initiator tRNA carrying the first amino acid in the protein - these components come together to form the initiation complex which is the molecular setup needed to make a new protein The tRNA carrying the methionine attaches to the small ribosomal subunit - they bind to the 5’ end of the mRNA by recognizing the 5’ GTP cap which was added during processing in the nucleus They go along the mRNA in the 3’ direction, stopping when they reach the start codon (eukaryotic cells) In bacteria, the small ribosomal subunit attaches directly to certain sequences in the mRNA - these Shine-Dalgarno sequences mark the start of each coding sequence, letting the ribosome find the right start codon for each gene. Elongation The amino acid chain gets longer and the mRNA is read one codon at a time, and the amino acid matching each codon is added to a growing protein chain Detailed: The first methionine- carrying tRNA (methionine is an amino acid specified by the start codon, AUG) starts out in the middle slot of the ribosome, called the P site. A...