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A reflection paper in 2 full pages with a Title. Mixed 3 chapters summaries and Self reaction.;Attachments Preview;BSC1020_Chapter10_PPT Lecture.pdf Download Attachment;BIOLOGY AND SOCIETY;Chapter 10;The Structure and Function;of DNA;Mix-and-Match Viruses;In 2009, a cluster of unusual flu cases broke out;around Mexico City.;In June 2009, the World Health Organization (WHO);declared H1N1 a pandemic (global epidemic) and;unveiled a massive effort to contain it.;Scientists soon determined that H1N1 was a hybrid;flu strain, made when a known flu virus mixed with;an Asian swine flu virus.;The hybrid H1N1 flu strain had a combination of;genes that infected young, healthy people instead of;the elderly or people who were already sick.;Many countries produced a coordinated response;and the WHO declared the pandemic over in August;2010.;Each year in the United States, over 20,000 people;die from influenza infection.;From 1918 to 1919, the deadliest pandemic killed;about 40 million people worldwide in just 18;months;These women are taking precautions against the 2009 H1N1 flu virus;in Mexico City.;Figure 10.0;DNA: STRUCTURE AND REPLICATION;DNA and RNA Structure;DNA;DNA and RNA are nucleic acids.;Was known to be a chemical in cells by the;end of the nineteenth century;They consist of chemical units called;nucleotides.;Has the capacity to store genetic information;A nucleotide polymer is a polynucleotide.;Can be copied and passed from generation to;generation.;Nucleotides are joined by covalent bonds;between the sugar of one nucleotide and the;phosphate of the next, forming a sugarphosphate backbone.;The discovery of DNA as the hereditary material;ushered in the new field of molecular biology;the study of heredity at the molecular level.;1;Phosphate;group;Nitrogenous base;Each nucleotide is composed;of three components;Nitrogenous base;(can be A, G, C, or T);Sugar;DNA;nucleotide;Thymine (T);DNA;double;helix;Phosphate;group;Sugar;(deoxyribose);Polynucleotide;Sugar-phosphate;backbone;DNA nucleotide;Figure 10.1;The sugar in DNA is deoxyribose. Thus, the full;name for DNA is deoxyribonucleic acid.;The four nucleotides found in DNA differ in their;nitrogenous bases. These bases are;Figure 10.1;Cytosine;An RNA;polynucleotide;Uracil;Adenine;Guanine;thymine (T), cytosine (C), adenine (A), and;guanine (G).;RNA differs from DNA in three main ways;Phosphate;It has uracil (U) in place of thymine;Sugar;(ribose);It has ribose instead of deoxyribose;It is typically single-stranded;Figure 10.2;Chapter Review Figure;Chapter Review Figure;DNA;Phosphate;group;Nitrogenous;base;C;G;A;T;Sugar;Nitrogenous;base;DNA;Deoxyribose;Ribose;Number of;strands;2;1;Sugar;Polynucleotide;RNA;Nucleotide;C;G;A;U;2;Watson and Cricks Discovery of the Double Helix;James Watson and Francis Crick determined that;DNA is a double helix.;Watson and Crick used X-ray crystallography data to;reveal the basic shape of DNA;Rosalind Franklin produced the X-ray image of DNA;Rosalind Franklin;X-ray image of DNA;Figure 10.3b;Figure 10.3a;The model of DNA is like a rope ladder twisted;into a spiral.;The ropes at the sides represent the sugarphosphate backbones.;Each wooden rung represents a pair of bases;connected by hydrogen bonds.;Twist;Figure 10.4;DNA bases pair in a complementary fashion;Hydrogen bond;adenine (A) pairs with thymine (T) via two;hydrogen bonds;cytosine (C) pairs with guanine (G) via three;hydrogen bonds;Therefore, the more C & G a DNA double helix;contains, the more stable it is;Blast Animation: Structure of DNA double helix;(a) Ribbon model;(b) Atomic model;(c) Computer model;Blast Animation: Hydrogen bonds in DNA;Figure 10.5;3;Hydrogen bond;DNA Replication;When a cell reproduces, a complete copy of the;DNA must pass from one generation to the next.;Watson and Cricks model for DNA suggested;that DNA replicates by a template mechanism.;The logic is simple: If you know the sequence of;bases in one strand, you can determine the;sequence of the other strand by base-pairing rules;Example: If sequence 1 is AGTC;then sequence 2 must be TCAG;(b) Atomic model;Parental (old);DNA molecule;DNA polymerases;Are enzymes;Make the covalent bonds between the;nucleotides of a new DNA strand;Daughter;(new) strand;Parental;(old) strand;Daughter DNA;molecules;(double helices);Are involved in repairing damaged DNA.;Note: DNA can be damaged by toxic chemicals;in the environment or by high energy radiation;such as X-rays and ultraviolet light.;Figure 10.6;DNA Replication;Origin of;replication;Origin of;replication;Parental strands;DNA replication in eukaryotes begins at specific;sites on a double helix (called origins of;replication) and;Origin of;replication;Parental strand;It then proceeds in both directions, creating;replication bubbles;Daughter strand;In eukaryotes, there are many origins of;replication per chromosome;Figure 10.7;Bubble;Eventually all the bubbles merge, yielding;two complete, and identical, double-stranded;DNA molecules;Two daughter DNA molecules;4;THE FLOW OF GENETIC INFORMATION;FROM DNA TO RNA TO PROTEIN;DNA Replication;DNA replication ensures that all the body cells in;multicellular organisms carry the same genetic;information.;DNA provides instructions to;a cell and;an organism as a whole.;It is also the means by which genetic information;is passed along to offspring;How are these instructions carried out?;BioFlix Animation: DNA Replication;How an Organisms Genotype Determines Its;Phenotype;An organisms genotype is its genetic makeup;the sequence of nucleotide bases in DNA.;The phenotype is the organisms physical traits;which arise from the actions of a wide variety of;proteins.;Example: Structural proteins help make up;the body of an organism, and enzymes;catalyze its metabolic activities;1. Transcription, the transfer of genetic;information from DNA into an RNA;molecule;2. Translation, the transfer of information from;RNA into a protein.;How an Organisms Genotype Determines Its;Phenotype;DNA;The major breakthrough in demonstrating the;relationship between genes and enzymes came in the;1940s from the work of American geneticists;George Beadle and Edward Tatum with the bread;mold Neurospora crassa.;TRANSCRIPTION;RNA;DNA specifies the synthesis of proteins in two;stages;Nucleus;Cytoplasm;TRANSLATION;Protein;Figure 10.8;Figure 10.9;5;Beadle and Tatum;studied strains of mold that were unable to grow;on the usual growth medium;determined that these strains lacked an enzyme in;a metabolic pathway that synthesized arginine;showed that each mutant was defective in a single;gene, and;hypothesized that the function of an individual;gene is to dictate the production of a specific;enzyme.;The one geneone enzyme hypothesis has since;been modified.;First, it was extended beyond enzyme to include;all proteins;Now it is stated as follows;The function of a gene is to dictate the;production of a polypeptide.;A protein may consist of two or more;different polypeptides.;From Nucleotides to Amino Acids: An Overview;What is the language of nucleic acids?;Genetic information in DNA is;transcribed into RNA, then;translated into polypeptides;In DNA, it is the linear sequence of;nucleotide bases.;A typical gene consists of thousands of;nucleotides in a specific sequence.;which then fold into proteins.;A single DNA molecule may contains;thousands of genes;Figure 10.10;When DNA is transcribed, the result is an RNA;molecule.;RNA is then translated into a sequence of amino;acids in a polypeptide.;Gene 1;Gene 2;DNA molecule;Gene 3;What are the rules for translating the RNA message;into a polypeptide?;DNA strand;TRANSCRIPTION;Experiments have verified that the flow of;information from gene to protein is based on a;triplet code.;A codon is a triplet of bases, which codes for;one amino acid.;RNA;TRANSLATION Codon;Polypeptide;Amino acid;6;The Genetic Code;Second base of RNA codon;UUU;The genetic code is the set of rules that convert a;nucleotide sequence in RNA to an amino acid;sequence.;61 code for amino acids;3 are stop codons, instructing the ribosomes to;end the polypeptide.;AUG has a dual function: i) Codes for methionine;and ii) Acts as start codon;UUC;UUA;UUG;First base of RNA codon;There are 64 codons (base triplets);U;Leucine;(Leu);CUU;C;CUC;CUA;AUA;AUG;GUC;GUA;CCA;Met or start;Stop;UGA Stop;Stop;UGG Tryptophan (Trp) G;CAC;CAA;CAG;AAU;ACC;ACA;AAC;Threonine;(Thr);AAA;ACG;AAG;GUG;GCC;GCA;GCG;U;UAA;CAU;Proline;(Pro);GAU;GCU;Valine;(Val);Cysteine;(Cys);UAC;ACU;Isoleucine;(Ile);GUU;G;UCG;CCC;G;UGU;Tyrosine;(Tyr);UAG;Serine;(Ser);CCG;AUU;AUC;UCA;A;UAU;CCU;Leucine;(Leu);CUG;A;C;UCU;Phenylalanine;UCC;(Phe);Alanine;(Ala);GAC;GAA;GAG;Histidine;(His);Glutamine;(Gln);UGC;CGA;Aspartic;acid (Asp);Glutamic;acid (Glu);U;Arginine;(Arg);CGG;AGU;Asparagine;AGC;(Asn);Lysine;(Lys);A;CGU;CGC;AGA;AGG;GGA;C;A;G;Serine;(Ser);Arginine;(Arg);GGU;GGC;C;U;C;A;G;Third base of RNA codon;U;U;Glycine;(Gly);C;A;G;GGG;Figure 10.11;Almost all of the genetic code is shared by all;organisms, from the simplest viruses and bacteria to;the most complex plants and animals;Thus, using modern DNA technologies, it is;possible to program one species to produce a;protein from another species by transplanting;DNA;Transcription: From DNA to RNA;Transcription;makes RNA from a DNA template;uses a process that resembles the synthesis of;a DNA strand during DNA replication, and;substitutes uracil (U) for thymine (T).;Example: Mice;expressing a;green fluorescent;protein (GFP) gene;from jellyfish;RNA nucleotides are linked by the transcription;enzyme RNA polymerase.;Figure 10.12;Figure 10.13;Initiation of Transcription;RNA;polymerase;RNA nucleotides;The start transcribing signal is a nucleotide;sequence called a promoter, which is located in;the DNA at the beginning of the gene.;The first phase of transcription is initiation, in;which;Newly;made;RNA;RNA polymerase attaches to the promoter;Template;strand of DNA;and;RNA synthesis begins.;(a) A close-up view of transcription;7;RNA Elongation;Termination of Transcription;During the second phase of transcription, called;elongation;During the third phase of transcription, called;termination;the RNA grows longer and;the RNA strand peels away from its DNA;template.;RNA polymerase reaches a special sequence;of bases in the DNA template called a;terminator, signaling the end of the gene;Blast Animation: Transcription;polymerase detaches from the RNA and the;gene, and;Blast Animation: Roles of RNA;the DNA strands rejoin.;Figure 10.13;The Processing of Eukaryotic RNA;RNA polymerase;DNA of gene;Promoter;DNA;1 Initiation;RNA;Terminator DNA;2 Elongation;In the cells of prokaryotes, RNA transcribed;from a gene immediately functions as messenger;RNA (mRNA), the molecule that is translated;into protein.;The eukaryotic cell;localizes transcription in the nucleus and;3 Termination;Growing RNA;modifies, or processes, the RNA transcripts in;the nucleus before they move to the;cytoplasm for translation by ribosomes.;Completed RNA;(b) Transcription of a gene;RNA polymerase;The Processing of Eukaryotic RNA;The Processing of Eukaryotic RNA;RNA processing includes;RNA splicing is believed to play a significant;role in humans;adding a cap and tail consisting of extra;nucleotides at the ends of the RNA transcript;removing introns (noncoding regions of the;RNA), and;RNA splicing, joining exons (the parts of the;gene that are expressed) together to form;messenger RNA (mRNA).;in allowing our approximately 21,000 genes;to produce many thousands more;polypeptides;and;by varying the exons that are included in the;final mRNA.;The end result is mature messenger RNA (mRNA);8;Translation: The Players;DNA;Transcription;Addition of cap and tail;Cap;RNA;transcript;with cap;and tail;Introns removed;Translation is the conversion from the nucleic;acid language to the protein language.;Tail;It involves more elaborate machinery than;transcription;Exons spliced together;mRNA;Coding sequence;BioFlix Animation: Protein Synthesis;Nucleus;Cytoplasm;Figure 10.14;Messenger RNA (mRNA);Transfer RNA (tRNA);The first important ingredient required for;translation is the mRNA produced by;transcription;Transfer RNA (tRNA) acts as a molecular;interpreter;The machinery used to translate mRNA requires;ATP;enzymes;ribosomes, and;Must carry out two distinct functions;1) Pick up the appropriate amino acid;2) Recognize the appropriate codon in mRNA;The unique structure of tRNA molecules enables;them to perform these two tasks;transfer RNA (tRNA).;Transfer RNA (tRNA);Figure 10.15;Amino acid attachment site;A tRNA molecule consists of a single;polynucleotide chain that twists and folds upon;itself;Hydrogen bond;It has two business ends;At one end, the amino acid attaches;RNA polynucleotide chain;At the other, there is a special triplet of bases;called the anticodon;It is complementary to the codon in;mRNA;Anticodon;tRNA polynucleotide;(ribbon model);tRNA;(simplified;representation);9;Ribosomes;Ribosomes are the sites of protein synthesis;The ribosome consists of three tRNA binding;sites;P site= Holds the tRNA carrying the growing;poplypeptide chain;A ribosome is made up of two subunits;Each subunit is made up of proteins and a;considerable amount of another kind of RNA;ribosomal RNA (rRNA).;A fully assembled ribosome holds tRNA and;mRNA for use in translation.;A site = Holds a tRNA carrying the next;amino acid to be added to the peptide chain;E (Exit) site = Provides the exit site for;tRNAs that have unloaded their amino acids;Note: This is not mentioned in the;textbook, but I added it to the next figure;tRNA binding sites;E site;P site;Next amino acid;to be added to;polypeptide;A site;Growing;polypeptide;Large;Ribosome;subunit;mRNA;binding;site;tRNA;mRNA;Small;subunit;Codons;(b) The players of translation;(a) A simplified diagram of a ribosome;Figure 10.16;Translation: The Process;Translation is divided into three phases;Figure 10.16;Initiation;Initiation brings together;mRNA;1. Initiation;the initiator tRNA, with the first amino acid;Methionine (Met), attached, and;2. Elongation;3. Termination.;Blast Animation: Translation;two subunits of the ribosome.;The mRNA molecule has a cap and tail that help;the mRNA bind to the ribosome.;10;Initiation;Cap;Start of genetic;message;Initiation occurs in two steps.;1. An mRNA molecule binds to a small;ribosomal subunit, then a special initiator;tRNA binds to the start codon, where;translation is to begin on the mRNA.;2. A large ribosomal subunit binds to the small;one, creating a functional ribosome.;End of genetic;message;Tail;Figure 10.17;Elongation;Met;Anticodon of tRNA;Initiator;tRNA;Large;ribosomal;subunit;Elongation occurs in three steps.;Step 1: Codon recognition.;P site;A site;The anticodon of an incoming tRNA;pairs with the mRNA codon at the A site;of the ribosome.;Codon of mRNA;mRNA;2;1;Start;codon;Small;ribosomal;subunit;Figure 10.18;Elongation;Step 2: Peptide bond formation.;Amino;acid;Polypeptide;The polypeptide leaves the tRNA in the;P site and attaches to the amino acid on;the tRNA in the A site.;The ribosome catalyzes the bond;formation between the two amino acids.;P site;Anticodon;mRNA;A site;Codons;Codon recognition;Peptide bond formation;ELONGATION;Figure 10.19;11;Elongation;Step 3: Translocation.;The tRNA that was in the P site leaves the;ribosome through the E site;The tRNA carrying the polypeptide moves;from the A to the P site.;New peptide;bond;E site;mRNA;movement;The mRNA and tRNA move as a unit;Translocation;Stop codon;This movement brings into the A site the;next mRNA codon to be translated, and the;process can start again with step 1;ELONGATION;Figure 10.19;Termination;Amino acid;Polypeptide;Elongation continues until a stop codon reaches;the A site of the ribosome;P site;Anticodon;mRNA;Stop codons do not specify amino acids;A site;Codons;1 Codon recognition;Rather, they signify the end of translation;ELONGATION;The completed polypeptide is freed, and the;ribosome splits into its subunits;Stop codon;2 Peptide bond formation;New peptide;bond;mRNA;movement;3 Translocation;Review: DNA RNA Protein;In a cell, genetic information flows from DNA to;RNA to protein;RNA polymerase;1 Transcription;Figure 10.19;Nucleus;DNA;mRNA;Intron;In eukaryotic cells, transcription occurs in the;nucleus and RNA is processed before it enters;the cytoplasm;Translation occurs on ribosomes in the cytoplasm;Codon;Cap;Tail;Intron;mRNA;5 Elongation;Polypeptide;Amino acid;tRNA;It is rapid: a single ribosome can make an;average-sized polypeptide in less than a;minute;Anticodon;2 RNA processing;A;Ribosomal;subunits;Stop;codon;Anticodon;ATP;Enzyme;3 Amino acid attachment;4 Initiation of;translation;6 Termination;Figure 10.20;12;Review: DNA RNA Protein;Review: DNA RNA Protein;As it is made, a polypeptide;Transcription and translation are how genes;control;coils and folds and;assumes a three-dimensional shape, its;tertiary structure.;Several polypeptides may come together;forming a protein with quaternary structure;Refer to Fig. 3.20;the structures of cells and;the activities of cells.;Or more broadly put, transcription and translation;govern the way the genotype produces the;phenotype;Mutations;A mutation is any change in the nucleotide;sequence of DNA.;Normal hemoglobin DNA;Mutant hemoglobin DNA;Mutations can change the amino acids in a;protein.;mRNA;mRNA;Mutations can involve;large regions of a chromosome or;Sickle-cell hemoglobin;Normal hemoglobin;Glu;Val;just a single nucleotide pair, as occurs in;sickle-cell disease.;Figure 10.21;Types of Mutations;Mutations within a gene can occur as a result of;base substitutions, deletions, or insertions;Base substitution is the replacement of one base;by another;Met;Lys;Phe;Gly;Ala;mRNA and protein from a normal gene;Because of redundancy of the genetic code;some substitution mutations have no effect;Example: A mutation that changes a GAA;codon to GAG. Since both code for the same;amino acid (Glu Gutamic acid), the change;is called a silent mutation;Met;Lys;Phe;Ser;Ala;(a) Base substitution;Figure 10.22;13;Types of Mutations;Types of Mutations;The previous mutation is called a missense;mutation, because it changes the encoded amino;acid;Nucleotide deletion is the loss of a nucleotide;Some base substitutions are called nonsense;mutations, because they change an amino acid;codon into a stop codon;Nucleotide insertion is the addition of a nucleotide;Insertions and deletions can;Example: A mutation that changes an AGA;(Arginine) codon to UGA (stop) codon;change the reading frame of the genetic;message, and so;The result will be a prematurely terminated;protein, which likely will not function properly;lead to disastrous effects;Met;Lys;Phe;Gly;Ala;mRNA and protein from a normal gene;Met;Lys;Phe;Deleted;Met;Lys;Leu;(b) Nucleotide deletion;Gly;Ala;mRNA and protein from a normal gene;Inserted;Met;Ala;Figure 10.22;Lys;(c) Nucleotide insertion;Leu;Trp;Arg;Figure 10.22;Mutagens;Mutations may result from;errors in DNA replication or recombination or;physical or chemical agents called mutagens.;Many mutagens can act as carcinogens, agents;that cause cancer;Although mutations are often harmful, they are;the source of genetic diversity, which is;necessary for evolution by natural selection.;Mutations are one source of the diversity of life visible in;this scene from the big island of Hawaii;Figure 10.23;14;VIRUSES AND OTHER NONCELLULAR;INFECTIOUS AGENTS;Viruses share some, but not all, characteristics of;living organisms. Viruses;possess genetic material in the form of;nucleic acids wrapped in a protein coat;are not cellular, and;cannot reproduce on their own.;In a sense, a virus is nothing more than genes in;a box.;Bacteriophages;Protein coat;DNA;Bacteriophages, or phages, are viruses that;attack bacteria.;They typically consist of an elaborate proteinbased structure consisting of;Head, which encloses a molecule of DNA;Tail, which is used to inject the DNA into the;host bacterial cell;Adenovirus causes;the common cold;The spikes in each corner help the;virus attach to a susceptible cell;Tail fibers, which are used for attachment;Figure 10.24;Bacteriophages;Head;Phages have two reproductive cycles.;1. In the lytic cycle;Bacteriophage;(200 nm tall);many copies of the phage are produced;within the bacterial cell, and;Tail;Tail;fiber;DNA;of virus;Bacterial cell;then the bacterium lyses (breaks open).;2. In the lysogenic cycle;the phage DNA inserts into the bacterial;chromosome and;the bacterium reproduces normally, copying;the phage at each cell division.;Colorized TEM;Figure 10.25;15;Phage;4;1 Phage;attaches;to cell.;Cell lyses;releasing;phages.;Phage;Phage DNA;Bacterial;chromosome (DNA);Phage injects DNA;1 Phage;attaches;to cell.;Phage DNA;Bacterial;chromosome (DNA);Phage injects DNA;Many cell;divisions;7 Prophage;may leave;chromosome.;LYTIC CYCLE;Phages assemble;2 Phage DNA;circularizes.;2;Phage DNA;circularizes.;LYSOGENIC;CYCLE;Prophage;3 New phage DNA and;proteins are synthesized.;6 Prophage replicated;at each normal cell;division.;5 Phage DNA is inserted into;the bacterial chromosome.;Figure 10.26;Figure 10.26;Plant Viruses;Phage lambda;Viruses that infect plants can;E. coli;stunt growth;diminish plant yields, and;spread throughout the entire plant.;Most known plant viruses have RNA rather than;DNA as their genetic material.;Many of them, like the tobacco mosaic virus;are rod-shaped with a spiral arrangement of;proteins surrounding the nucleic acid.;Figure 10.26;Plant Viruses;Viral plant diseases have no cure;Agricultural scientists focus on;RNA;Protein;preventing infections, and;on breeding or genetically engineering plants;that resist viral infection.;Tobacco mosaic virus;Figure 10.27;16;Animal Viruses;Membranous;envelope;Viruses that infect animals cells;Protein spike;RNA;are a common cause of disease and;may have RNA or DNA genomes.;Some animal viruses steal a bit of host cell;membrane as a protective envelope;Protein coat;It contains projections of protein spikes;which are used to attach to host animal cells;The influenza virus contains eight separate molecules of;RNA, each wrapped in a protein coat;Figure 10.28;Animal Viruses;Mumps virus;The mumps virus is an example of an enveloped;RNA virus;Protein spike;Envelope;It causes a once-common childhood disease;characterized by fever and swelling of the;salivary glands;Colorized TEM;It has been almost eliminated by vaccination;The reproductive cycle of enveloped RNA;viruses can be broken into seven steps.;Figure 10.29;Protein spike;Virus;4 Protein;synthesis;mRNA;Protein coat;Viral RNA;(genome);Envelope;1;Entry;2;Plasma membrane;of host cell;RNA synthesis;by viral enzyme;New viral;genome;Uncoating;3;5 RNA synthesis;(other strand);Template;New;viral proteins;6;Assembly;Viral RNA;(genome);Exit;7;Figure 10.29;Figure 10.29;17;The Process of Science;Do Flu Vaccines Protect the Elderly?;The Process of Science;Do Flu Vaccines Protect the Elderly?;Observation: Vaccination rates among the;elderly rose from 15% in 1980 to 65% in 1996.;Experiment: Tens of thousands of people over;the age of 65 were followed during the ten flu;seasons of the 1990s.;Question: Do flu vaccines decrease the mortality;rate among those elderly people who receive;them?;Percent reduction in severe;illness and death in;vaccinated group;Hypothesis: Elderly people who were;immunized would have fewer hospital stays and;deaths during the winter after vaccination.;Results: People who were vaccinated had a;27% less chance of being hospitalized during;the next flu season and;48% less chance of dying.;48;50;40;30;27;20;16;10;0;0;Winter months;(flu season);Hospitalizations;Summer months;(non-flu season);Deaths;Figure 10.30;Figure 10.30;HIV, the AIDS Virus;The devastating disease AIDS (acquired;immunodeficiency syndrome) is caused by HIV;(human immunodeficiency virus);HIV is a retrovirus, an RNA virus that reproduces by;means of a DNA molecule.;Envelope;Surface protein;Protein;coat;RNA;(two identical;strands);Retroviruses use the enzyme reverse transcriptase;to synthesize DNA on an RNA template.;HIV steals a bit of host cell membrane as a protective;envelope.;Reverse;transcriptase;Blast Animation: HIV Structure;Figure 10.31;18;Cytoplasm;Reverse;transcriptase;Viral RNA;1;DNA;strand;Nucleus;Chromosomal;DNA;2;Provirus;3;Doublestranded;DNA;4;SEM;5;RNA;Viral;RNA;and;proteins;6;HIV (red dots) infecting a white blood cell;The behavior of HIV nucleic acid in an infected cell;can be broken into six steps.;Figure 10.32;Figure 10.32;HIV infects and eventually kills several kinds of white;blood cells that are important in the bodys immune;system.;While there is no cure for AIDS, its progression can be;slowed by two categories of medicine that interfere with;the reproduction of the virus;Thymine;(T);The first type inhibits the protease enzymes, which;help produce the final versions of HIV proteins;The second type, which include the drug AZT;inhibits the HIV enzyme reverse transcriptase;Part of a T nucleotide;AZT;Blast Animation: AIDS Treatment Strategies;Figure 10.33;Viroids and Prions;Two classes of pathogens are smaller than;viruses.;1. Viroids are small, circular RNA molecules;that infect plants.;2. Prions are misfolded proteins that somehow;convert normal proteins to the misfolded;prion version, leading to disease.;Viroids and Prions;Prions are responsible for neurodegenerative;diseases including;mad cow disease;scrapie in sheep and goats;chronic wasting disease in deer and elk, and;Creutzfeldt-Jakob disease in humans.;19;Evolution Connection;Emerging Viruses;Emerging viruses are viruses that have suddenly;come to the attention of science.;Examples are;H1N1;Avian flu.;An outbreak of mad cow disease in England required;the culling of hundreds of thousands of cows.;Figure 10.34;Evolution Connection;Emerging Viruses;Avian flu;infects birds;infected 18 people in Hong Kong in 1997, and;since has spread to Europe and Africa, infecting;over 400 people and killing over 250 of them.;Over 100 million birds have either;died from the disease or;been killed to prevent the spread of infection.;Rounding up ducks in India to help prevent the spread;of the Avian flu virus;Figure 10.34;Evolution Connection;Emerging Viruses;If avian flu mutates to a form that can easily;spread between people, the potential for a major;human outbreak is significant.;New viruses can arise by;the mutation of existing viruses or;the spread of existing viruses to a new host;species.;20;View Full Attachment;BSC1020_Chapter11_PPT Lecture.pdf Download Attachment;Chapter 11;How Genes Are Controlled;Biology and... Show more;BSC1020_Chapter12_PPT Lecture.pdf Download Attachment;A Closer Look: Cutting and Pasting DNA with;Restriction Enzymes;Chapter 12;A recombinant DNA molecule is created by;combining two ingredients;DNA Technology;A bacterial plasmid (a piece of;nonchromosomal DNA);A human gene of interest;To understand how these DNA molecules are;spliced together, you need to learn how enzymes;cut and paste DNA;A Closer Look: Cutting and Pasting DNA with;Restriction Enzymes;The cutting tools used to make recombinant;DNA are bacterial enzymes called restriction;enzymes;There are hundreds of these enzymes, each;recognizing a particular short DNA sequence;(usually 4-8 bases long);After a restriction enzyme binds to its;recognition sequence, it cuts the two strands of;DNA at specific points within the sequence;Recognition site (recognition sequence);for a restriction enzyme;1 A restriction enzyme cuts the;DNA into fragments.;DNA;Restriction;enzyme;another source.;base pairing.;Figure 12.9;DNA called restriction fragments with;sticky ends important for joining DNA;from different sources;DNA ligase, which connects the DNA pieces;into continuous strands by forming bonds;between adjacent nucleotides.;DNA PROFILING AND FORENSIC SCIENCE;DNA profiling;has rapidly revolutionized the field of forensics;the scientific analysis of evidence from crime;scenes.;3 Fragments stick together by;into strands.;the restriction enzyme, which produces pieces of;can be used to determine if two samples of;genetic material are from a particular individual;and;2 A DNA fragment is added from;4 DNA ligase joins the fragments;The production of recombinant DNA actually;requires two enzymes;DNA;ligase;Recombinant DNA molecule;To produce a DNA profile, scientists compare;sequences in the genome that vary from person to;person.;1;Figure 12.13;Investigating Murder, Paternity, and Ancient DNA;Overview of DNA Profiling;1 DNA isolated Crime scene Suspect 1 Suspect 2;DNA profiling can be used to;test the guilt of suspected criminals;identify tissue samples of victims;2 DNA amplified;resolve paternity cases;identify contraband animal products, and;trace the evolutionary history of organisms.;3 DNA compared;Figure 12.14;DNA Profiling Techniques;The Polymerase Chain Reaction (PCR);The polymerase chain reaction (PCR) is a;technique to copy quickly and precisely a;specific segment of DNA;It can generate enough DNA, from even;minute amounts of blood or other tissue, to;allow DNA profiling.;Analysis of DNA extracted from Cheddar Man a 9,000 year old;skeleton found in an English cave suggested that he was a direct;ancestor of this local schoolteacher;Figure 12.15;Short Tandem Repeat (STR) Analysis;How do you test if two samples of DNA come;from the same person?;DNA Amplification;By PCR;Repetitive DNA;Initial;DNA;segment;makes up much of the DNA that lies between;genes in humans and;consists of nucleotide sequences that are;present in multiple copies in the genome.;1;2;4;8;Number of DNA molecules;2;Short Tandem Repeat (STR) Analysis;Crime scene DNA;Short tandem repeats (STRs) are;short sequences of DNA and;repeated many times, tandemly (one after;another), in the genome.;STR analysis;STR site 2;STR site 1;AGAT;Same number of;short tandem repeats;GATA;Different numbers of;short tandem repeats;is a method of DNA profiling and;compares the lengths of STR sequences at;specific sites in the genome.;AGAT;GATA;Suspects DNA;Figure 12.16;Gel Electrophoresis;Gel Electrophoresis;The lengths of DNA fragments are compared;using gel electrophoresis;The DNA samples are placed in separate wells;(holes) at one end of a flat, rectangular gel;which is a jellylike material that acts as a;molecular sieve;It is a method for sorting macromolecules;usually proteins or nucleic acidsprimarily by;their;Electrical charge;Size.;Blast Animation: Gel electrophoresis;A negatively-charged electrode is then placed at;the DNA-containing end of the gel, and a;positive electrode at the other end;DNA is negatively-charged because of its;phosphate (PO4) groups, and so the fragments;move through the gel towards the positive pole;Gel Electrophoresis;Gel Electrophoresis;However, longer DNA fragments move more;slowly through the thicket of polymer fibers in;the gel;The bands can be made visible by;Thus, over time, shorter molecules move;farther through the gel;When the current is turned off, a series of bands;is left in each lane of the gel;Each band is a collection of DNA fragments;of the same length;1) Staining them with chemicals;2) Exposure onto photographic film (if the DNA;is radioactively labeled);3) Measuring fluorescence (if the DNA is;labeled with a fluorescence dye);The differences in the locations of the bands;reflect the different lengths of the DNA;fragments.;3;Mixture of DNA;fragments of;different sizes;Amplified;crime scene;DNA;Band of longest;(slowest) fragments;Amplified;suspects;DNA;Longer;fragments;Power;source;Shorter;fragments;Band of shortest;(fastest) fragments;Figure 12.17;Figure 12.18;RFLP Analysis;Gel electrophoresis may also be used for RFLP;analysis;Crime scene DNA;Suspects DNA;Fragment w;Cut;RFLP (pronounced rif-lip) stands for;restriction fragment length polymorphism;Fragment z;Restriction;enzymes;added;Fragment x;In this method, DNA molecules are exposed to a;restriction enzyme, producing fragments that are;compared and made visible by gel electrophoresis;Cut;Cut;Fragment y;Fragment y;Blast Animation: DNA fingerprinting;Figure 12.19;Chapter;Review;Figure;Crime scene;DNA;Longer;fragments;Suspects;DNA;DNA;Polymerase chain;reaction (PCR);amplifies STR;sites;z;x;Shorter;fragments;w;y;Crime scene Suspect 1 Suspect 2;y;Longer;DNA;fragments;Gel;Shorter;DNA;fragments;DNA fragments compared by gel electrophoresis;Figure 12.19;(Bands of shorter fragments move faster toward the positive pole.);4


Paper#17972 | Written in 18-Jul-2015

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