2 RNA Genes are coded DNA instructions that control protein production First, DNA must be copied to RNARNA structure: identical to DNA except:Sugar = Ribose (not deoxyribose)N base = C, G, A, and Uracil (U) (replaces thymine)Single-stranded
3 Types of RNA Main function RNA: to assemble amino acids into proteins Messenger RNA (mRNA): carry copies of instructions to make proteins from DNA in nucleus → cytoplasm (ribosomes)Ribosomal RNA (rRNA): help make ribosomesTransfer RNA (tRNA): transfers amino acids to ribosomes for protein assembly
4 TranscriptionTranscription: process by which portion of DNA is copied to complementary RNA sequence inside nucleusRequires RNA polymerase (an enzyme)Binds to DNA and separates strandsUses DNA strand as template to make RNA complement
5 The Genetic Code “Language” of mRNA instructions Read 3 letters at a time, called a codon, that specify a single amino acid64 total possible codons → 20 amino acidsExample:UCGCAG = UCG + CAGSerine + Glutamine… → Protein (polypeptide)
6 TranslationTranslation: the decoding of an mRNA sequence into amino acids on ribosomesBegins at AUG (“start” codon)Codons of mRNA match up with Anticodons of complementary tRNATranslation continues until a “stop” codon is read (UAA, UAG, UGA)Result is chain of new proteins!!
7 Protein AssemblyAmino acids connect with peptide bonds to form proteins (“polypeptides”)Proper synthesis of proteins is essential to organism survivalProteins are enzymes – control most chemical reactionsi.e.: photosynthesis, cellular respiration, etc.“By coding for proteins, DNA holds the key to life”Protein Synthesis