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Chapter 10 - Nucleic Acids and Protein Synthesis I. DNA (Deoxyribonucleic acid) A. Structure of DNA 1. polymer made of nucleotides (Monomer) a. deoxyribose sugar b. phosphate group c. nitrogen-containing base (makes one nucleotide different from another) 2. Bases a. purines (2 carbon rings) 1) adenine (A) and guanine (G) b. pyrimidines (1carbon ring) 1) cytosine (C) and thymine (T)- only in DNA; Uracil (U)- ONLY in RNA 3. complementary base pairing a. C-G and A-T b. connected by hydrogen bonds (weak bonds) 1) C and G have 3 2) A and T have 2 4. double helix (proposed by Watson and Crick model- 1953) a. 2 nucleotide chains that wrap around each other (like a spiral staircase) * inspired by x-ray photograph of DNA crystals by Rosalind Franklin * sugar on outside * 2 strands DNA and Base Couples b. ladder model 1) sides - alternating deoxy. sugar and phosphate 2) rungs - nitrogen bases attached to deoxy. sugar a) purine always attached to a pyrimidine 3) hydrogen bonds hold two half ladders together (between H and an O or an N atom) c. nucleotide sequence of one half is exact complement of other half http://www.youtube.com/watch?v=qy8dk5iS1f0&feature=related B. Replication of DNA (occurs in the Nucleus) 1. process of copying DNA in a cell 2. enzymes called helicases break H bonds and 2 sides separate 3. DNA polymerase enzyme assembles new DNA half using nucleotides found in nucleus 4. each half serves as a template (pattern) to make a new half 5. two exact copies of original DNA produced (due to complementary nature of nucleotides) 1) each has one old and one new half http://www.youtube.com/watch?v=4jtmOZaIvS0 6. mutation - a change in the nucleotide sequence II. RNA (Ribonucleic acid) A. Structure of RNA 1. ribose sugar 2. uracil replaces thymine 3. single strand 4. Types of RNA a. messenger RNA (mRNA) - carries genetic info. from DNA to cytoplasm (ribosome) b. transfer RNA (tRNA)(cloverleaf) - binds to specific amino acids c. ribosomal RNA (rRNA) - makes up ribosomes III. Protein Synthesis (production of proteins) A. Transcription 1. process where genetic info. is copied from DNA to RNA a. DNA is blueprint for all proteins b. proteins made at ribosomes c. DNA can’t leave nucleus 2. RNA polymerase (transcription enzyme) binds to promoter (beginning of a single gene) (Gene- small section of a chromosome that determines a specific trait) 3. DNA section (gene) separates 4. RNA polymerase attaches to DNA nucleotide and adds complementary RNA nucleotide 5. continues till RNA poly. reaches termination signal (marks end of gene) 6. mRNA leaves nucleus B. Proteins 1. polymers made of polypeptides (made of amino acids) 2. 20 amino acids C. The Genetic Code 1. sequence of mRNA nucleotides translated into sequence of amino acids 2. codon - sequence of 3 mRNA bases that code for a specific amino acid a. start codon (AUG)(methionine) - starts translation b.stop codon - (UAA, UAG, UGA) cause translation to stop D. Translation 1. assembling amino acids from mRNA code 2. tRNA transports amino acids to ribosome (region that binds to specific amino acid)3. (opposite amino acid attachment site) - sequence of 3 bases complementary to a specific codon (ANTICODON) a. insures that amino acids added in order prescribed by mRNA 4. ribosomes (free and attached) have one binding site for mRNA and two for tRNA 5. ribosome attaches to start codon and moves along to each codon until stop codon reached a. matching of anticodon and codon causes amino acids to join previous one and form peptide bond b. several ribosomes may translate same mRNA http://www.wisc-online.com/objects/index_tj.asp?objID=AP1302 http://www.youtube.com/watch?v=KvYEqGb7XN8&feature=related http://www.youtube.com/watch?v=NJxobgkPEAo Human Genome Project: Has discovered 20,000 genes