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Molecular Biology Chapter 9 DNA – Deoxyribonucleic Acid DNA stores genetic information copied and passed from generation to generation Directs the copying of itself DNA Replication Involved in protein production Transcription Translation History of DNA – Watson & Crick Wanted to know if the genetic material was protein or DNA. 1953 Deduce exact structure of DNA Nucleic Acid Double Helix Made of nucleotides James Watson (left) and Francis Crick Rosalind Franklin X-ray images of DNA DNA Structure Double Helix is composed of a Backbone composed of alternating Sugar Phosphate Rungs Bases 5-C sugar = Deoxyribose Adenine (A) Thymine (T) Guanine (G) Cytosine (C) Nucleotide = Phosphate + Sugar + Base © 2013 Pearson Education, Inc. FIGURE 9.3 (a) Each DNA nucleotide is made up of a sugar, a phosphate group, and a base. (b) Cytosine and thymine are pyrimidines. Guanine and adenine are purines. Phosphate group Nitrogenous base Sugar DNA nucleotide DNA double helix Nitrogenous base (can be A, G, C, or T) Thymine (T) Phosphate group Sugar (deoxyribose) DNA nucleotide Polynucleotide Sugar-phosphate backbone Hydrogen bond (b) Atomic model DNA Replication – semiconservative replication Parental (old) DNA molecule Daughter (new) strand Parental (old) strand Daughter DNA molecules (double helices) RNA - Ribonucleic Acid Structure of RNA: Sugar is Ribose No T, Uracil (U) instead Single stranded (ss) Figure 10.UN03b Nitrogenous base Sugar Number of strands DNA RNA C G A T C G A U DeoxyRibose ribose 2 1 How do DNA and RNA work together? DNA makes a copy of itself in the form of RNA transcription RNA is used to make proteins Translation * Please note DNA replication is a completely separate process that is NOT related to transcription and/or translation! Figure 10.UN05 TRANSCRIPTION TRANSLATION Gene mRNA DNA Polypeptide Types of RNA 1. Messenger RNA (mRNA) Carries the message from DNA directions for making a protein Types of RNA con’t. 2. Transfer RNA (tRNA) Carries and transfers amino acids to mRNA Types of RNA con’t. 3. Ribosomal RNA (rRNA) Mixed with protein to make ribosomes Two subunits (large & small) used to facilitate translation Figure 9.19 The protein synthesis machinery includes the large and small subunits of the ribosome, mRNA, and tRNA. (credit: modification of work by NIGMS, NIH) Figure 10.UN06 Growing polypeptide Amino acid Large ribosomal subunit tRNA mRNA Anticodon Codons Small ribosomal subunit http://highered.mheducation.co m/sites/0072507470/student_vi ew0/chapter3/animation__how_ translation_works.html