RNA & Protein Synthesis

RNA and Protein Synthesis Genes are coded DNA instructions that control the production of proteins within the cell DNA codes for PROTEINS Must copy part of the nucleotide sequence from DNA into RNA (ribonucleic acid) which then helps make proteins –Proteins are made in ribosomes – need RNA to go to ribosomes as the DNA cannot leave the nucleus

Structure of RNA Long chain of nucleotides –A 5-carbon sugar (ribose) –A phosphate group –And nitrogenous bases Differences between RNA and DNA: –Ribose (RNA) vs. deoxyribose (DNA) –RNA is single-stranded, DNA is double-stranded –RNA has Uracil (U) in place of Thymine (T) –In RNA, A bonds with U, and C bonds with G RNA is a disposable copy of DNA – it is a working copy of a single gene

RNA Base-Pairing Rule A = U G = C

Types of RNA Protein synthesis – assembly of amino acids into proteins controlled by RNA Three types of RNA –Messenger RNA (mRNA) – carry copies of instructions for making amino acids –Ribosomal RNA (rRNA) – proteins assembled on ribosomes –Transfer RNA (tRNA) – transfers each amino acid to ribosome mRNA tRNA

fromtoto make up also calledwhich functions toalso called which functions to can be RNA Messenger RNA Ribosomal RNA Transfer RNA mRNACarry instructions rRNA Combine with proteins tRNA Bring amino acids to ribosome DNARibosomeRibosomes Types of RNA

Transcription: DNA RNA (pages in book) Occurs in NUCLEUS for eukaryotes RNA produced by copying part of the nucleotide sequence of DNA into a complementary sequence in RNA = transcription (RE- WRITING DNA to RNA) During transcription, RNA polymerase (similar to DNA polymerase) binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of mRNA RNA polymerase binds to specific regions of DNA in order to start making mRNA called promoters. The end region is called a terminator. In Eukaryotes, the RNA is “processed” first and then becomes mRNA which then leaves the nucleus. (ex. Introns removed since they don’t code for genes)

RNA DNA RNA polymerase Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) Transcription

The Genetic Code & Intro to Translation (pages in book) Translation is taking mRNA and making proteins Proteins become your traits! Proteins are made by joining amino acids into long chains called polypeptides There are 20 different amino acids – the order of amino acids determine what proteins will be made “Language” of mRNA instructions is the genetic code – codes for proteins RNA contains four bases A, U, C, and G – where A and U can bond together and C and G can bond together

The Genetic Code (continued)  Genetic code is read THREE letters at a time, so that each “word” of coded message is 3 bases long. Each 3 letter “word” in mRNA is called a codon which identifies a single amino acid used in a protein Example: mRNA sequence – UCGCACGGU Read 3 bases at a time – UCG – CAC – GGU Codons represent different amino acids UCG – CAC – GGU Serine – Histadine – Glycine What is the DNA sequence that coded for this mRNA sequence? AGCGTGCCA

The Genetic Code (continued) Some amino acids can be specified by more than one codon (because there are only 20 amino acids, and 64 possible codons, some codons will overlap) 3 “stop” codons – signal the end of a protein Codon AUG specifies methionine – a “start” codon for the beginning of the protein A chart is used to decode the codons into their respective amino acids

The Genetic Code mRNA Sequence: UCG CAC GGU

mRNA Sequence: UCG CAC GGU