Making Proteins

Proteins What is a protein? Long chain of amino acids hooked together Only 20 amino acids exist, but they can be combined countless ways

Proteins & Genes Genes have instructions for what amino acids link together and in what order they should be linked 1 gene has the directions for 1 protein DNA molecules are just genes after genes after genes (directions for proteins, after proteins…

What determines the order of amino acids? THE GENETIC CODE! The genetic code consists of only 4 letters! A, T, G and C A and G are called purines T and C are called pyrimidines Purines always bond with pyrimidines A – T and G – C.

What determines the order of amino acids? The order of nucleotides/nitrogen bases determines what amino acids are used to make a protein Codon—set of three nitrogen bases in a row that code for an amino acid

How many codons are present? How many amino acids will be made? T G A A C T G T T A T A How many codons are present? How many amino acids will be made? 4 4

Protein Synthesis Has two parts Transcription Translation

Transcription Creating a copy of mRNA from DNA DNA does not turn into mRNA DNA must stay in the nucleus where it is protected and cannot be destroyed mRNA will leave the nucleus, and go the ribosome where the protein will be made The mRNA copy is COMPLEMENTARY not identical to DNA

Differences between DNA & RNA Sugar Phosphate group Nitrogen bases Strands Deoxyribose Ribose Same Same A C G T A C G U Two One

Practice transcription G C T A T C A A T C G G C G A U A G U U A G C C T T A A T A C G T T C G G A A U U A U G C A A G C C C C A C G T G C A T G G U G C A C G U A A G C T T A G C C A T U C G A A U C G G U A DNA mRNA

Translation Actual protein construction, mRNA provides the instructions to join amino acids together Transfer RNA (tRNA) with the help of ribosomal RNA (rRNA) reads the mRNA Occurs at the ribosome Anticodon—set of three nitrogen bases on tRNA that match a codon on mRNA

DNA TTT ACC TAC mRNA AAA UGG AUG lys trp met