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Replication Transcription Translation DNA 1. Double Stranded Helix 2. Hydrogen Bonds between Nitrogenous Base Pairs 3. Adenine-Thymine and Guanine-Cytosine Replication • The duplication of DNA which occurs during the S phase of Interphase. • 1 Strand 2 Complementary Strands • DNA Polymerase Hydrogen bond (H-bonds) thymine adenine cytosine guanine phosphate deoxyribose sugar Sugar / phosphate “strand” Nitrogenous base “rung” DNA nucleotide Deoxyribose sugar phosphate RNA nucleotide ribose sugar Nitrogenous base (guanine) phosphate Nitrogenous base (uracil) Step 1: Hydrogen bonds between complimentary bases break DNA “unzips” Step 2: DNA strands pull apart from each other Step 3: DNA nucleotides in the cell match up with each side of the “unzipped” DNA each “unzipped’ strands forms a template for a new strand Step 4: Each “old’ strand forms a template for a “new” strand two identical DNA molecules form “new” strand, identical sequence to the original “old” (original) strand Transcription • The process by which a molecule of DNA is copied into a complementary strand of RNA. • 1 Strand DNA 2 Strands RNA • RNA Polymerase • Semiconservative • Difference between • replication and • transcription DNA RNA Step 1: Hydrogen bonds between complimentary bases break DNA “unzips” Step 2: DNA strands pull apart from each other Step 3: RNA nucleotides in the cell match up with only one side of the “unzipped” DNA each “unzipped’ strands forms a template for a mRNA strand RNA nucleotide Step 4: RNA nucleotides continue to match up with “unzipped” DNA until the message is completely transcribed mRNA strand One side of DNA strand mRNA strand Step 4: mRNA strand breaks off from the DNA strand One side of DNA strand Step 5: mRNA strand leaves the nucleus for the ribosome Step 6: Once the mRNA leaves, the DNA “zips” back together Where rep, transl, transc occur Translation • The process in which the information in the nucleotide base sequence of mRNA is used to dictate the amino acid sequence of a protein. • 1 Strand RNA Amino Acid Chain Protein The problem: How does a particular sequence of nucleotides specify a particular sequence of amino acids? By means of transfer RNA molecules, each specific for one amino acid and for a particular triplet of nucleotides in mRNA called a codon. The family of tRNA molecules enables the codons in a mRNA molecule to be translated into the sequence of amino acids in the protein. RNA and Protein Synthesis • RNA is a Single Stranded Nucleic Acid • RNA Acts as a Messenger between DNA and Ribosomes • Process Takes Amino Acids and Forms Proteins Why Is It Necessary? • DNA / Nucleus • Ribosomes / Cytoplasm • Need a Messenger Definitions • Codon 1. Three-base segment of mRNA that specify amino acids. 2. Sense Codons 3. Nonsense Codons • Anticodon 1. Three-base segment of tRNA that dock with a codon. 2. Docking results in deposition of amino acid. Protein Synthesis • Proteins are coded directly from the mRNA with 3 bases (one codon) for each amino acid. What’s up with that? Mutation • A change in the nitrogenous base sequence of DNA; that change causes a change in the product coded for by the mutated gene. Mutations What happens when you get insertions or deletions of bases in the DNA sequence? Usually you end up with a mess. THE BIG FAT CAT ATE THE RAT AND GOT ILL Deletion of one base THE IGF ATC ATA TET HER ATA NDG OTI LL And its all pops and buzzes. Sickle-Cell Anemia Definitions • Carcinogens Substances and preparations which, if they are inhaled or ingested or if they penetrate the skin; may induce cancer or increase its incidence and can affect any cells or tissues • Mutagens may induce hereditary genetic defects or increase their incidence and effect the germ cells (gonads) • Teratogens may induce non-hereditary congenital malformations or increase their incidence and effect the growing fetus Mutagens • • • • • • • Tobacco products Nitrous Acid Mold Toxins X-rays Gamma Rays UV Radiation Some Artificial Sweeteners