Molecular Biology
DNA Replication…review strands are complementary; nucleotides line up on template according to base pair rules. SEMI-CONSERVATIVE?
DNA Replication
Replication - DNA doubles, and the cell divides. The DNA doubles during INTERPHASE The cell divides in MITOSIS – when it goes through the phases PMAT iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii PMAT
Leave Replication behind us…
CENTRAL DOGMA of Molecular Biology PROTEIN SYNTHESIS
Protein Synthesis: overview Transcription: synthesis of RNA under the direction of DNA (DNA mRNA) Translation: actual synthesis of a polypeptide under the direction of mRNA (mRNA Protein) PROTEINS determine TRAITS
The Triplet Code The genetic instructions for a polypeptide chain are ‘written’ in the DNA as a series of 3-nucleotide ‘words’ Codons (3 mRNA bases) Remember : ‘U’ (uracil) replaces ‘T’ in RNA
Transcription: overview
Translation vocabulary mRNA from nucleus is ‘read’ along its codons by tRNA’s anticodons at the ribosome tRNA has an amino acid attached to one side, an anticodon on the other
Translation
Why Do We Need Proteins? Cell Structure Cell = 80% protein Cell membrane
Why Do We Need Proteins? Cell Processes Hormones (signals) Enzymes (speed up reactions)
Why Do We Need Proteins? Membrane Channels (remember transport?) Neurotransmitters (carry nerve/brain messages)
What Do We Need For Protein Synthesis? 2. RNA mRNA = (messenger RNA) makes and takes copy of DNA to cytoplasm tRNA = (transfer RNA) Matches w/ mRNA on ribosome and carries AA to add to protein chain
What Do We Need For Protein Synthesis? 3. Ribosome Reads mRNA Directs tRNA Creates peptide bonds between AAs (makes polypeptide chain)
What Do We Need For Protein Synthesis? 4. Amino Acids (AAs) Building blocks of proteins (20 AAs exist) Protein = AA chain = polypeptide chain ORDER MATTERS! AA order determines function of protein
Steps of Protein Synthesis Transcription (writing the “message”) DNAmRNA messenger carries code to cytoplasm Translation (reading the “message”) mRNA tRNA protein (AA chain) message translated into a protein
Steps of Protein Synthesis (Nucleus) (Cytoplasm)
Transcription DNA to mRNA Location = nucleus Steps a. Enzyme binds to DNA, unzips it b. mRNA copy of gene made from DNA template *U replaces T in RNA
3 DNA nucleotides (triplet) to mRNA codon Transcription 3 DNA nucleotides (triplet) to mRNA codon Codons
Translation mRNA to tRNA to protein (AA chain) Location = cytoplasm (first codon in mRNA is the start codon)
Translation Steps of Translation 1. mRNA moves to cytoplasm, binds to ribosome 2. tRNA anticodon UAC brings AA (methionine) to mRNA codon on ribosome
Translation 3. Ribosome moves down mRNA to next codon 4. tRNA anticodon brings & attaches next AA with peptide bond
Translation 5. tRNA leaves ribosome once AA attached Protein chain AA mRNA
Translation 6. Steps 1-5 repeated, adding AAs until STOP CODON signals end of protein 7. Polypeptide chain released from ribosome
Synthesis Practice TAC AUG UAC GGA CCU GGA CCT GGA CCU TAT AUA UAU AGA DNA (triplet) mRNA (codon) tRNA (anti-codon) TAC AUG UAC GGA CCU GGA CCT GGA CCU TAT AUA UAU AGA UCU AGA ACT UGA ACU
Synthesis Practice ACT AGA TAT CCT GGA TAC ACU UGA UCU UAU AUA CCU UAC DNA (triplet) ACU UGA UCU UAU AUA CCU UAC AUG tRNA (anti-codon) mRNA (codon) Amino Acid Met (Start) Methionine Pro Proline Gly Glycine Ile Isoleucine Ser Serine Stop