CHAPTER 10 Molecular Biology of the Gene Figures 10 1 10 5 PowerPoint Lecture Slides for Essential Biology Second Edition Essential Biology with Physiology Neil Campbell Jane Reece and Eric Simon Presentation prepared by Chris C Romero Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings THE STRUCTURE AND REPLICATION OF DNA DNA Was known as a chemical in cells by the end of the nineteenth century Has the capacity to store genetic information Can be copied and passed from generation to generation Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings DNA and RNA Polymers of Nucleotides DNA and RNA are nucleic acids They consist of chemical units called nucleotides The nucleotides are joined by a sugar phosphate backbone Fig 10 3 to Fig 10 5 p 174 5 Nucleic acids consist of long chains polymers of chemical units monomers Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings 1 Phosphate group Nitrogenous base Sugar Nitrogenous base A G C or T Nucleotide Thymine T Phosphate group Sugar deoxyribose DNA nucleotide Polynucleotide Sugar phosphate backbone Figure 10 2 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings The four nucleotides found in DNA Differ in their nitrogenous bases Are thymine T cytosine C adenine A and guanine G RNA has uracil U in place of thymine Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Watson and Crick s Discovery of the Double Helix James Watson and Francis Crick determined that DNA is a double helix a James Watson and Francis Crick Figure 10 3a Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings 2 Watson and Crick used X ray crystallography data to reveal the basic shape of DNA Rosalind Franklin collected the X ray crystallography data b Rosalind Franklin Figure 10 3b Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings The model of DNA is like a rope ladder twisted into a spiral Twist Figure 10 4 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Detailed representations of DNA Notice that the bases pair in a complementary fashion Hydrogen bond a b c Figure 10 5 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings 3 DNA Replication When a cell or organism reproduces a complete set of genetic instructions must pass from one generation to the next Fig 10 6 p 176 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Watson and Crick s model for DNA suggested that DNA replicated by a template mechanism Parental old DNA molecule Daughter new strand Daughter DNA molecule double helices Figure 10 6 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings DNA can be damaged by ultraviolet light The enzymes and proteins involved in replication can repair the damage Figure 10 7 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings 4 DNA replication Begins at specific sites on a double helix Proceeds in both directions Origin of replication Origin of replication Origin of replication Parental strand Daughter strand Bubble Two daughter DNA molecules Figure 10 8 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings How an Organism s DNA Genotype Produces Its Phenotype An organism s genotype its genetic makeup is the sequence of nucleotide bases in DNA The phenotype is the organism s specific traits Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings DNA specifies the synthesis of proteins in two stages Nucleus DNA Transcription RNA Transcription Translation Translation Protein Cytoplasm Figure 10 9 P 177 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings 5 The one gene one protein hypothesis states that the function of an individual gene is to dictate the production of a specific protein Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings From Nucleotide Sequence to Amino Acid Sequence An Overview The information or language in DNA is ultimately translated into the language of polypeptides Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings What is the language of nucleic acids In DNA it is the linear sequence of nucleotide bases DNA molecule Gene 1 Gene 2 Gene 3 DNA strand Transcription RNA Translation Codon Polypeptide Amino acid Figure 10 10 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings 6 When DNA is transcribed the result is an RNA molecule RNA is then translated into a sequence of amino acids in a polypeptide Translation is the conversion of the nucleic acid language into the polypeptide language P 178 Like nucleic acids polypeptides are polymers but the monomers that make them up are the 20 amino acids common to all organisms Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings What is the correspondence between the nucleotides of an RNA molecule and the amino acids of a polypeptide If A T G C coded for only one amino acid 4 of 20 If they code in combinations of two lettered words 42 16 of 20 amino acids Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Triplets of bases Specify all the amino acids The triplets are called codons Fig 10 10 p 178 Codons in figure 10 11 p 179 are triplets found in RNA Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings 7 The Genetic Code The genetic code is the set of rules relating nucleotide sequence to amino acid sequence Figure 10 11 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Transcription From DNA to RNA In transcription Genetic information is transferred from DNA to RNA An RNA molecule is transcribed from a DNA template Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings RNA nucleotides RNA polymerase Newly made RNA Direction of transcription Template strand of DNA a A close up view of transcription Figure 10 13a Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings 8 Transcription of an entire gene RNA polymerase DNA of gene Promoter DNA Initiation RNA Elongation Terminator DNA Area shown in part a Termination Growing RNA Completed RNA b Transcription of a gene RNA polymerase Figure 10 13b Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Initiation of Transcription The start transcribing signal is a nucleotide sequence called a promoter The first phase of transcription is initiation RNA polymerase attaches to the promoter RNA synthesis begins Copyright 2004 Pearson Education Inc publishing as Benjamin