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Protein Synthesis From DNA to protein And viruses And bacteria CENTRAL DOGMA: From DNA to Protein • OVERVIEW FIRST Central Dogma Youtube (3:01) • DNA wrapping, transcription, translation Youtube (7:46) Central Dogma • You Tube Protein Synthesis (2:51) • DNA Transcription and Protein Assembly (3:02) From DNA to proteins • FROM GENOTYPE TO PHENOTYPE (From DNA to proteins) First Proposed by • Francis Crick (1958) • Later : Nirenberg said, "DNA makes RNA makes protein." Beadle and Tatum REMEMBER US? • Using Neurospora crassa bread mold determined "one gene - one enzyme hypothesis" Protein Synthesis Overview get “Central Dogma” and “Protein Synthesis” Worksheets • DNA Replication, Transcription, Translation Youtube (8 mins) Learn these Terms • Transcription = DNA → mRNA • Translation = mRNA → protein Three Bases Lingo • DNA Triplet ATC • mRNA Codon UAG tRNA Anti-codon AUC The 3 RNA’s • mRNA – messenger RNA – codes from DNA in the nucleus to take the genetic code to the ribosome in the cytoplasm • tRNA – transfer RNA – brings a specific amino acid to the ribosome + cytoplasm • rRNA –ribosomal RNA – plus protein makes up a ribosome ANIMATIONS • McGraw-Hill Transcription Animation • McGraw-Hill Translation Animation Transcription: DNA to mRNA McGraw Hill Transcription Animation • DNA never leaves the nucleus • It codes to mRNA to take the message outside the nucleus • TRANSCRIPTION YOUTUBE (1:53) • Transcription (1:27) RNA polymerase (RNAP) • The enzymes that makes RNA from the DNA template DNA RNAP RNA REMEMBER: U replaces T in all RNA’s Not all RNA nucleotides make the cut: Introns and Exons • Primary mRNA = exons + introns • INTRONS = discarded, noncoding region of mRNA • EXONS = the coding regions, spliced together RNA are called also = Mature mRNA • RNA Splicing Youtube (1:38) SPLICING RNA Or Primary RNA Mature mRNA SPLICING ANIMATION snRNP’s Spliceosome McGraw-Hill How Splicesosomes Process RNA • Before the mRNA leaves the nucleus, the introns are removed, and the exons are spliced together. Exons leave the nucleus Mature mRNA leaves Transcription Initiation Control Transcription Promotors • DNA sequences at start site (recognize TATA BOX) TATA • RNA polymerase and accessory proteins (transcription factors) bind to the promoter to initiate production of an mRNA transcription. Transcription Terminator • mRNA is cut free from DNA The mRNA travels out of the nucleus through nuclear pores to a ribosome in the cytoplasm The mRNA binds to a ribosome Ribosome translates codons (use chart) TRANSLATION • Coding from mRNA to making protein (at the ribosome) • DNA Translation Youtube (2:06) TRANSLATION • mRNA (genetic language) needs to be translated into protein language (chain of amino acids) • Transcription Youtube (2:06) tRNA • transports amino acids to ribosomes • There is a specific amino acid for each tRNA • Anticodon for that amino acid Job of tRNA • Complements the codon of mRNA and picks up the appropriate amino acid tRNA animation (1:29) Note the A P E sites Central Dogma youtube (3:03) • A site – Amino acid is dropped off • P site – Polypeptide builds • E site – tRNA exits (after giving its amino acid to building polypeptide chain) APE sites of Ribosome youtube (1:31) McGraw Hill EPA 2:24 A P E Sites at the Ribosome Translocation movement of tRNA across the ribosome TRANSLATION Virtual Cell Animation (Nice APE sites) (3:32) There are 20 Amino Acids • These 20 are shared by all living organisms • What does CAC code for? • histidine Notice AUG codon means “start” building a new protein. UAA, UAG, UGA mean “stop’ building the protein. Translation Initiation • mRNA attaches to the ribosome (AUG –start codon) Translation Elongation tRNA brings amino acids to the ribosome Translation Termination video 1:01 mRNA reaches one of the STOP codons • Bond breaks the last tRNA and its amino acid to release the polypeptide bond Cooooool Protein Synthesis 3-D • CENTRAL DOGMA (2:52) transcription translation All mRNA’s start with AUG, so all DNA genes start with______? Answer •Methionine • Is always the STARTamino acid GENE REGULATION pp. 210-11 • Remember that question on the DNA Extraction lab: “Do all cells in your body have the same DNA?” • YES • Just not all genes are expressing at the same time. EXAMPLE: Lac operon • E. coli used to produce lactose-using enzymes: • lacZ codes for β-galactosidase • lacY for lactose permease • lacA codes for galactoside O-acetyltransferase Gene Expression • Gene promoter = where RNA polymerase attaches and initiates transcription • Operator = acts like a switch – between promoter and genes • Represser = turns off transcription-binds to operator and blocks RNA polymerase OPERON = • Operator + represser + promoter + genes GENE REGULATION turning on and off of genes • Lac operon control 2:09 • McGraw Hill Lac Operon • THINK: • What would happen if something caused the base sequence to change? • What sorts of things could cause this? • Could the base changes be repaired? • Would those changes be passed on to the individual’s offspring? Thalidomide baby… MUTATION: A change in the base sequence of a gene resulting in a different base sequence and thus different amino acid sequence. What causes mutations? MUTAGENS MUTAGEN • = any source of mutation is a physical or chemical agent –EX: X-rays –UV light –cigarette components –Hazardous chemicals Mutagens Mutation Animations • BBC - Education Scotland - Higher Bitesize Revision - Biology - Genetics and adaptation - Mutations: Revision 2 • EXPLAIN HOW EACH MUTATION IS DIFFERENT FROM THE ORIGINAL DNA SEQUENCE Mutation Lingo • Mutation = any change in nucleotide sequence of DNA • Reading frame = triplet grouping • Mutagenesis = creation of mutations Gene (point)mutations SUBSTITUTION – Replace one base for another. Minimal effect ADDITION – Adding a base DELETION – removing a base Addition/deletions cause a complete Frame Shift that affects the whole gene. FRAMESHIFT MUTATION (1:24) More Mutation Lingo • Nonsense mutation = change an amino acid into a STOP codon • Missence mutation = change the amino acid coding • Silent mutation = no change in protein product What type of mutation is this? • SILENT What type of mutation is this? • MISSENSE What type of mutation is this? • NONSENSE Chromosome Mutations has moved Translocation one segment • of a chromosome to a different Chromosome translocation youtube • Inversion • Segment of a same chromosome is turned end to end • Inversions 2:05 Translocation Translocation 9 and 22 Cystic Fibrosis Deletion ALBINISM Albinism is due to a mutation of the melanin pigment gene. A one base substitution results in only 1 amino acid being in error. AAGGTTCGGAGT (DNA) type of mutation Amino acids AACGTTCGGAGT:____________________ AAGGTCTCGGAGT:____________________ AAGGTTCGAGT:_______________________ AAGGTTCGGAGT (DNA) type of mutation Amino acids AACGTTCGGAGT:Substitution(C for G) AAGGTCTCGGAGT:_Insertion (the C) AAGGTTCGAGT:__Deletion (the G) Chromosomal mutations Affect the entire chromosome often fatal. We will look at this kind in Chapter 9. Oncogenes Genes that when mutated result in cancer. EXAMPLE: BRCA1 and BRCA2 Found to cause breast cancer on 81-kb region of human chromosome 17 VIRUSES a small infectious agent that can replicate only inside the living cells of an organism Viruses • Nothing more than packaged genes • Simple tools for geneticists • HIV EBOLA Viral Infections Bacteriophage Infection (SEM) Bacteriohage Infection Every virus has two stages • a dormant, particulate, transmissible stage called the virion stage (usually protein coat + DNA or RNA) • an active, intracellular stage called the infectious stage Infectious Stage: Lytic Infection 1.attachment 2. Insertion of virus DNA 3. replication of virus components 4.packaging and assembly of new virions 5. exit from cell –”lysis” bursts The Lytic Cycle Bacteriophage protein coat Bacteriophage DNA Bacterial chromosome Bacteriophage attaches to bacterium’s cell wall Bacteriophage enzyme lyses the bacterium’s cell wall, releasing new bacteriophage particles that can attack other cells. Lytic Cycle Bacteriophage proteins and nucleic acids assemble into complete bacteriophage particles Bacteriophage takes over bacterium’s metabolism, causing synthesis of new bacteriophage proteins and nucleic acids Go to Section: Bacteriophage injects DNA into bacterium Bacteriophage Bacteriophage DNA Bacteriophage protein LYTIC INFECTION • Lytic Infection Animation Lysogenic Infection • The viral DNA becomes integrated into the bacterial DNA after infection. It is replicated along with the host DNA when the host reproduces. The viral DNA is referred to as a prophage. A Lysogenic Infection Bacterial chromosome Bacteriophage DNA Bacteriophage injects DNA into bacterium Bacteriophage DNA (prophage) can exit the bacterial chromosome Lytic Cycle Bacteriophage enzyme lyses the bacterium’s cell wall, releasing new bacteriophage particles that can attack other cells Lysogenic Cycle Bacteriophage proteins and nucleic acids assemble into complete bacteriophage particles Go to Section: Bacteriophage DNA (prophage) may replicate with bacterium for many generations Bacteriophage DNA forms a circle Prophage Bacteriophage DNA inserts itself into bacterial chromosome DIAGRAM COMPARISON • Lytic and Lysogenic Infections Virus Examples • RNA instead of DNA: cold, flu, HIV, polio, measles, mumps • DNA viruses: herpes. Chicken pox, hepatitis • Herpes infections may flare up when under stress, a cold, or sunburn Viroid • Virus in plants Virion • An entire virus particle, consisting of an outer protein shell called a capsid and an inner core of nucleic acid PRION • an infectious agent composed of protein in a misfolded form. • EXAMPLE: Mad Cow Disease - BSE Emerging Viruses • a virus that has adapted and emerged as a new disease/pathogenic strain • EXAMPLES: Influenza • Hanta Virus • Ebola • Nipah Why are viruses called • GENES IN A BOX • They are usually a genetic material (DNA or RNA) inside a protein coat Ebola Virus • Causes hemorrhagic fever • Movie Outbreak Hanta Virus • Southwestern US mice carried it cardiovascular collapse, respiratory failure, and death HIV • • • • Is the virus that causes AIDS Has 2 copies of RNA Is a retrovirus (RNA to DNA) Carry enzyme reverse transcriptase (codes backwards RNA to DNA) Aids infected cells • HIV = Human Immunodeficiency Virus • AIDS = Acquired Immune Deficiency Syndrome BACTERIA • Prokaryotic • One-celled F Factor • Fertility factor • Allows one bacterium to carry genes to another by conjugation Sex pili Bacterium Plasmid • Circular DNA in bacteria • Extra genes, not essential for bacterial survival Transformation • Uptake of DNA from another bacteria cell Conjugation • Physical union of two bacterial cells to transfer DNA R Plasmid • Contain genes that are resistant to many antibiotics Transduction • Some viruses move bacterial DNA from one bacterial cell to another