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Biochemistry: Nucleic Acids November 3, 2007 Bio099 Timberlake Chapter 17 Martinin Pages 54-55 Nucleic Acids: The Big Picture Two Types of Nucleic Acids Two Types 1. DNA Deoxyribonucleic acid Two Types of Nucleic Acids Two Types 1. DNA Deoxyribonucleic acid 2. RNA Ribonucleic acid Nucleotide The monomer of nucleic acids Molecular Components of the nucleotide 1. Pentose sugar DNA RNA Molecular Components of the nucleotide 1. Pentose sugar 2. Phosphate group Molecular Components of the nucleotide 1. Pentose sugar 2. Phosphate group 3. Nitrogenous bases purine pyrimidine Nitrogenous Bases BASES OF DNA BASES OF RNA Nucleoside Primary Structure of Nucleic Acids • Nucleotides are bound together to form nucleic acids. Primary Structure of Nucleic Acids • Nucleotides are bound together to form nucleic acids. – The sequence of bases is like an instruction manual that can be read by the cell. Secondary Structure of Nucleic Acids • DNA: The Double Helix The vertical blue strand represents the sugar and phosphate group and the inner horizontal bands represent the nitrogenous bases Secondary Structure of Nucleic Acids • DNA: The Double Helix – Complementary base pairs Secondary Structure of Nucleic Acids • DNA: The Double Helix – Complementary base pairs – Helical Secondary Structure of Nucleic Acids • RNA: Single stranded, but loopy in structure DNA Replication • Each time a cell divides, its entire genome must be copied and passed on to the new cell. DNA Replication • 1 double helix replicates to give 2 new double helixes DNA Replication • 1 double helix replicates to give 2 new double helixes • The 2 new DNA molecules are made of 1 OLD and 1 NEW polynucleotide strands The Steps of DNA Replication 1. The two DNA strands are unwound with the help of the enzyme HELICASE which facilitates the breaking of the chemical bonds between the molecules. The Steps of DNA Replication 2. DNA POLYMERASE helps to form bonds between the nucleotides of the newly formed strand. Protein Synthesis The Big Picture DNA (instructions) RNA (copy of instructions) Protein (result of following instructions) Protein Synthesis requires 3 types of RNA DNA RNA Protein Three Types of RNA 1. messenger RNA (mRNA) copy of a gene (DNA) leaves nucleus to carry genetic information to the ribosome for protein synthesis Three Types of RNA 2. ribosomal RNA (rRNA) part of the ribosome Three Types of RNA 3. transfer RNA (tRNA) • • • transfers the amino acids to the ribosome for protein synthesis. Steps of Protein Synthesis 1. Transcription of the genetic material. • making the mRNA. Steps of Protein Synthesis 2. The mRNA travels to the cytoplasm. Steps of Protein Synthesis 3. Translation of the mRNA • The word translation is used because the language is changing from nucleic acids to amino acids. • A genetic code is used by the cell to translate the genetic material (mRNA) into a protein • 3 nucleotides of mRNA make a codon that translates to a specific amino acid, or a start or stop message during protein synthesis. Steps of Protein Synthesis 3. Translation of the mRNA is initiated with a start codon. Steps of Protein Synthesis 4. Translation of the genetic material continues and the polypeptide gets longer. Steps of Protein Synthesis 5. Termination occurs when a stop codon is reached. Genetic Mutations • Mutations are changes in the sequence of nucleotides in DNA. G U G A U C • Mutations within a gene can alter the sequence of amino acids in a protein causing changes, or lack of protein function. Types of Mutations • Substitution Types of Mutations • Substitution Types of Mutations • Frameshift Genetic Mutations and Disease • A mutation in the gene that encodes the protein leptin leads to marked obesity in rodents and humans. Genetic Diseases • For more examples of genetic diseases caused by mutations see Timberlake Table 17.5