1. Molecular Genetics Protein Synthesis Overview

2. The Central Dogma DNA contains the blueprint for protein synthesis, but proteins are synthesized outside of the nucleus Does DNA need to exit and re-enter the nucleus? If so, how does it avoid being damaged? How can proteins be synthesized at different rates if there is only 1 complete set of DNA in every cell?

3. The Central Dogma The central dogma of molecular genetics is that protein synthesis occurs as a two-step process: –transcription - copying of information in DNA into mRNA (messenger RNA) –translation - using the mRNA blueprint to create a chain of amino acids (involves ribosomes)

4. The Central Dogma

5. Ribonucleic Acid (RNA) DNARNA deoxyribose sugarribose sugar double strandedsingle stranded A-T, C-GA-U, C-G in nucleusin nucleus and in cytoplasm

6. RNA Types of RNA: –messenger RNA (mRNA) - information from DNA is transcribed onto mRNA; length depends on length of gene transcribed –transfer RNA (tRNA) - transfers amino acids to ribosome to build polypeptide –ribosomal RNA (rRNA) - structural component of ribosome

7. Overview of Transcription Initiation –RNA polymerase binds to DNA at the promoter site (near the beginning of the gene) Elongation –using DNA template, RNA polymerase adds ribonucleotides to build mRNA transcript Termination –RNA polymerase recognizes signal to stop transcription (termination sequence)

8. Overview of Translation Initiation –ribosome recognizes specific sequence on mRNA and binds to that site Elongation –ribosome moves along mRNA 3 nucleotides at a time; tRNA delivers amino acids to elongate polypeptide chain Termination –3-base “stop” signal reached and ribosome falls off the mRNA, releasing polypeptide chain

9. Genetic Code codon - 3-base sequence on mRNA that codes for a specific amino acid start codon - does not code for an amino acid; signals initiation stop codon - does not code for an amino acid; signals termination

10. Genetic Code