Understanding the Process of DNA Transcription and Translation: From Genotype to Phenotype, Study notes of Biology

Download Understanding the Process of DNA Transcription and Translation: From Genotype to Phenotype and more Study notes Biology in PDF only on Docsity! 1 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings 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 CHAPTER 10 Molecular Biology of the Gene Figures 10.1 – 10.5 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • DNA THE STRUCTURE AND REPLICATION OF 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 are nucleic acids DNA and RNA: Polymers of Nucleotides – 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). 2 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Figure 10.2 Phosphate group Nitrogenous base Sugar Nucleotide Polynucleotide Sugar-phosphate backbone Nitrogenous base (A,G,C, or T) Thymine (T) Phosphate group Sugar (deoxyribose) DNA nucleotide 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 • James Watson and Francis Crick determined that DNA is a double helix. Watson and Crick’s Discovery of the Double Helix Figure 10.3a(a) James Watson and Francis Crick 5 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • DNA replication – Begins at specific sites on a double helix – Proceeds in both directions Figure 10.8 Origin of replication Origin of replication Origin of replication Parental strand Daughter strand Bubble Two daughter DNA molecules Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • An organism’s genotype, its genetic makeup is the sequence of nucleotide bases in DNA How an Organism’s DNA Genotype Produces Its Phenotype – 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 – Transcription – Translation Figure 10.9. P. 177 DNA Nucleus Transcription RNA Translation Protein Cytoplasm 6 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • 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 • The information, or “language,” in DNA is ultimately translated into the language of polypeptides From Nucleotide Sequence to Amino Acid Sequence: An Overview 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 Figure 10.10 DNA molecule Translation Polypeptide Gene 1 Gene 2 Gene 3 DNA strand Transcription RNA Codon Amino acid 7 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • 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 10 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • The third phase of transcription is termination Termination of Transcription – RNA polymerase reaches a sequence of DNA bases called a terminator Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • The eukaryotic cell processes the RNA after transcription The Processing of Eukaryotic RNA Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • RNA processing includes – Adding a cap and tail – Removing introns – Splicing exons together Figure 10.14 DNA RNA transcript with cap and tail mRNA Exon Intron Exon Intron Exon Cap Introns removed Tail Exons spliced together Coding sequence Nucleus Cytoplasm Transcription Addition of cap and tail 11 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • Translation Translation: The Players – Is the conversion from the nucleic acid language to the protein language Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • mRNA Messenger RNA (mRNA) – Is the first ingredient for translation Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • tRNA Transfer RNA (tRNA) – Acts as a molecular interpreter – Carries amino acids – Matches amino acids with codons in mRNA using anticodons Figure 10.15 Amino acid attachment site Hydrogen bond RNA polynucleotide chain Anticodon Anticodon 12 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • Ribosomes Ribosomes – Are organelles that actually make polypeptides, p. 183 – Are made up of two protein subunits – Contain ribosomal RNA (rRNA) Figure 10.16a tRNA binding sites P site A site P A Large subunit mRNA binding site Small subunit (a) Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • A fully assembled ribosome holds tRNA and mRNA for use in translation Figure 10.16b Next amino acid to be added to polypeptide Growing polypeptide mRNA tRNA (b) Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • Translation is divided into three phases Translation: The Process – Initiation – Elongation – Termination 15 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Polypeptide Amino acid P site Anticodon mRNA A site Codons Elongation 2 3 Translocation Codon recognition Peptide bond formation • The process of elongation Figure 10.19 mRNA movement New peptide bond 1 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • Elongation continues until the ribosome reaches a stop codon Termination Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • The flow of genetic information in a cell Review: DNA
RNA
Protein 16 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Figure 10.20 1 2 3 4 Amino acid attachment 5 Elongation Initiation of translation 6 Termination Transcription RNA processing RNA Polymerase Nucleus DNA RNA transcript Intron Tail Intron mRNA CAP tR N A Enzyme Amino acid Ribosomal subunits Anticodon Codon Stop codon Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • In eukaryotic cells – Transcription occurs in the nucleus – Translation occurs in the cytoplasm Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • Transcription and Translation – Are the processes whereby genes control the structures and activities of cells 17 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • A mutation Mutations – Is any change in the nucleotide sequence of DNA Figure 10.21 Normal hemoglobin Sickle-cell hemoglobin Glu Val Normal hemoglobin DNA Mutant hemoglobin DNA mRNA mRNA Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • Mutations within a gene Types of Mutations – Can be divided into two general categories – Can result in changes in the amino acids in proteins Figure 10.22a mRNA Protein Met Lys Phe Gly Ala (a) Base substitution Met Lys Phe Ser Ala Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • Insertions and deletions – Can have disastrous effects – Change the reading frame of the genetic message Figure 10.22b Met Lys Leu Ala His (b) Nucleotide deletion mRNA Protein Met Lys Phe Gly Ala 20 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • The reproductive cycle of an enveloped virus, p. 190 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Figure 10.29 VIRUS Entry1 2 3 4 Uncoating RNA synthesis by viral enzyme 5 RNA synthesis (other strand) Protein synthesis 6 Assembly 7 Exit Viral RNA (genome) Protein spike Protein coat Envelope Plasma membrane of host cell mRNA New viral proteins Template New viral genome Mumps virus, p.190 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • HIV is a retrovirus HIV, the AIDS Virus, p. 192 – A retrovirus is an RNA virus that reproduces by means of a DNA molecule – It copies its RNA to DNA using reverse transcriptase Figure 10.30a Envelope Protein Protein coat RNA (two identical strands) Reverse transcriptase (a) HIV 21 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings 1 2 3 4 5 6 DNA strand Viral RNA Reverse transcriptase Cytoplasm Double- stranded DNA Chromosomal DNA Provirus DNA Viral RNA and proteins Nucleus (b) The behavior of HIV nucleic acid in an infected cell • How HIV reproduces inside a cell Figure 10.30b Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • DNA and RNA: Polymers of Nucleotides SUMMARY OF KEY CONCEPTS Visual Summary 10.1 DNA Polynucleotide Nitrogenous base Phosphate group Nucleotide Sugar Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • DNA Replication Visual Summary 10.2 Parental DNA molecule Identical daughter DNA molecules 22 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • Translation: The Players Visual Summary 10.3 Large ribosomal subunit Amino acid mRNA tRNA Anticodon Codons Small ribosomal subunit