2/25/15. The Experiment. Griffith. GO Avery! Avery TRANSFORMATION. o animations.html

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1 o animations.html o Revisit the difference b/w a contagious and a genetic disease Griffith The Experiment o Isolated two strains (versions) of pneumonia bacteria from mice o Smooth colony caused disease o Rough colony was harmless Bad! Good TRANSFORMATION Information is exchanged. Bad! Good Heat killed Bad + Good Heat killed Bad Avery GO Avery! o Repeated Griffith s work to pinpoint what exactly the live bacteria absorbed o BUT this time destroyed lipid, CHO, protein, and nucleic acids o Only when DNA was gone did transformation not occur o DNA is nucleic acid that stores and transmits genetic information from one generation to the next! 1

2 Hershey-Chase o Bacteriophage--virus that can infect and kill bacteria o Bacteriophage consist of: n DNA or RNA core n Protein coat o Is it DNA or protein that infects? The Results o Tagged DNA with radioactive phosphorus o Tagged protein with radioactive sulfur o Virus infected bacteria and all the radioactivity was phosphorus! o Genetic material = DNA Chargaff s Rules o Percentage of guanine (G) and cytosine (C) are equal in any sample of DNA o Same holds true with adenine (A) and thymine (T) Rosalind Franklin o Aimed a powerful x- ray beam at concentrated DNA o X-shaped pattern suggests the spring like shape or helix o Watson and Crick using Franklin s x- ray pictures built the first model of the DNA The Double Helix The Double Helix: A Closer Look o Sugar and phosphate make up the backbone o The nitrogenous bases form the ladder rungs n Hydrogen bonds hold the bases together n A goes with T, G goes with C 2

3 The Perfect Compliment DNA s job o Each strand has the information needed to reconstruct the other half o This is called complementary o 1. Carry information from one generation to the next. o 2. Use the information it carries to determine traits. o 3. Has to be easily copied so that every time a cell divides it gets an exact replica. What is DNA made of? o Monomers called nucleotides o Nucleotides made of: n 5 carbon sugar called deoxyribose n Phosphate group n Nitrogenous base Nitrogenous bases o Purines have two rings n Adenine n Guanine o Pyrimidines one ring n Cystosine n Thymine Replication The Enzyme Factor o DNA separates into two strands o Base pair rules (Chargaff) follow n TACGTT ATGCAA o The result: two DNA molecules identical to each other and to the original molecule Replication Fork o DNA helicase unzip DNA by breaking hydrogen bonds o DNA polymerase joins nucleotides ( rezips ) to form the polymer, DNA n Also proofreads 3

4 Making a new protein o 1. Transcription--copy the information o 2. Translation--reading the information RNA o Ribonucleic acid n Ribose vs deoxyribose n Uracil vs thymine n Single strand vs double strand Types of RNA Transcription o Messenger RNA n Carries information from DNA to ribosome o Ribosomal RNA n Where proteins are assembled o Transfer RNA n Carries amino acid to ribosome o RNA molecules are produced by copying part of DNA nucleotide sequence into RNA complementary sequence RNA Editing o When RNA made some sequences are junk o Introns DNA sequence not expressed o Exons DNA sequence that will be expressed The Language of mrna o Language is read 3 bases at a time n 3 bases = codon n Each codon = amino acid (aa) o UCGCACGGU becomes o UCG*CAC*GGU becomes aa1 * aa2 * aa3 4

5 Secret Decoder Ring Step 1:Transcription o Messenger RNA transcribed from DNA o Released from nucleus into cytoplasm Step 2: Translation o mrna attaches to ribosome o Ribosome reads or translates the mrna into a protein o Ribosome reads the codon o The right amino acid is brought over by trna o Each trna has 3 bases called the anticodon; this decides what kind of aa it can carry Decode mrna into a protein Genetic Code o Proteins long chains of amino acids (aa) linked together to make a polypeptide o Properties of protein are determined by the order of the aa Amino Acid Protein Review 5

6 Mutations o Mistake made in copying their own DNA o Two major types n Gene mutation change in a single gene n Chromosomal mutation changes in the whole chromosome o Also called point mutations o Types: Types of Gene Mutations n Substitutions one base is changed n Insertion base is inserted n Deletion base is deleted Frameshift o When a nucleotide is added or deleted the bases are still read in groups of threes therefore. o Every aa that follows is misread Point Mutations o Cystic Fibrosis (CF) n Produce thick mucus n Caused by deletion of 3 base pairs o Sickle cell Disease n Just one DNA base is changed Types of Chromosomal Mutations Chromosomal Disorders o Deletion loss of all or part of a chromosome o Duplication produce extra copies or parts of the chromosome o Inversion direction of parts of chromosomes are reversed o Translocations part of chromosome breaks off and attaches to another o Nondisjunction error in meiosis when homologous chromosomes do not come apart n Trisomy 21 or Down s syndrome n Klinefelter s sydrome XXY NORMAL A B C D E F G H I 6

7 2/25/15 Why do mutations matter? o Provide a source of genetic variability Selective Breeding Induced Mutations o Chemicals o Radiation Inbreeding o Allowing only those animals/plants with desired characteristics to carry on o Breeding of individuals with similar characteristics Manipulating DNA o Genetic engineering rewriting DNA o DNA extraction open cells and separate DNA o Cutting DNA use restriction enzyme, a specific scissor, that cuts DNA o Separating DNA use gel electrophoresis 7

8 Gene Therapy o An absent or faulty gene is replaced with a normal working gene using a virus Transgenic Organisms o Organisms that contain genes from other species n Microorganisms used to mass produce insulin, growth hormone, clotting factor n Animals used to study genes and improve food supply n Plants used to produce plants that produce a natural insecticide Cloning Gel Electrophoresis o Nucleus is removed from an egg cell o Cell is fused with a cell taken from another adult o Fused cell divides as an embryo o Implanted in a foster mother o DNA is placed in a gel o Electrical current is applied o DNA moves towards positive end o Smaller fragments move faster Mrs. C? Kayla Polymerase Chain Reaction (PCR) o DNA heated to separate strands o Cooled to allow the primers to anneal o DNA polymerase goes to work making copies between the primers Human Genome Project o Started with Escherichia coli n Contains 4,639,221 base pairs o Try to decode human DNA sequence o Ethics? 8

9 Chromosomes o Chromatin is DNA tightly coiled around proteins called histones o The DNA with the histones from a beadlike structure called a nucleosome o The nucleosomes pack together tightly to form the chromosome Histone Nucleosome RNA polymerase Chromosome Inactivation o Binds to DNA o Separates DNA strands o Uses one strand of DNA as a template to compose a strand of RNA o Promoters specific regions of DNA where RNA polymerase will only bind to o Females have two X s: XX o Males just one: XY o Barr body--in females one X is on and off randomly switched off Gene Regulation o Promoters helps transcription to get started n TATA box short sequence of DNA: TATATA or TATAAA n Helps position RNA polymerase o Enhancer n Located before the promoter n Lots of proteins can bind here p Can enhance transcription by opening chromatin p Help attract polymerase p Can block access to genes Hox genes o Hox genes control differentiation n Decides how and where body parts grow n Birth defects may occur because Hox genes are disrupted Enhancer Promoter TATA box Transcription starts here Promoters 9

10 Transformation DNA Fingerprinting o A cell takes in DNA from an outside source o Plasmid circular DNA in bacteria (separate from the major DNA) n Contains a genetic marker helps to distinguish the bacteria that have the plasmid from those that don t o Analyzes sections of DNA that vary widely from individual to individual o Use restriction enzymes to cut specific regions o Separate by electrophoresis o Is the sample more like A or B? Testing for Alleles o Can spot the differences found in alleles that code for diseases such as Cystic Fibrosis o Use labeled DNA probes that contain complements specific to the alleles in question 10