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Protein Synthesis From DNA to protein And viruses And bacteria 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) Beadle and Tatum REMEMBER US? George Beadle and Edward Tatum during the late 1930s and early 1940s • 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 • rRNA –ribosomal RNA – plus protein makes up a ribosome Transcription: DNA to mRNA • DNA never leaves the nucleus • It codes to mRNA to take the message outside the nucleus • TRANSCRIPTION YOUTUBE (1:53) RNA polymerase (RNAP) • The enzymes that makes RNA from the DNA template DNA RNAP RNA 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 Seriously detailed splicing youtube (1:39) 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 • mRNA (genetic language) needs to be translated into protein language (chain of amino acids) • Translation Youtube (2:06) TRANSLATION • Coding from mRNA to making protein (at the ribosome) • DNA Translation Youtube (2:06) tRNA • transports amino acids to ribosomes • There is a specific amino acid for each tRNA Job of tRNA • Complements the codon of mRNA and picks up the appropriate amino acid ANIMATION: Animation of Translation 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) A P E Sites at the Ribosome Translocation: movement of tRNA across the ribosome Notice AUG codon means “start” building a new protein. UAA, UAG, UGA mean “stop’ building the protein. There are 20 Amino Acids • These 20 are shared by all living organisms • What does CAC code for? • histidine Translation Initiation • mRNA attaches to the ribosome (AUG – start codon) Translation Elongation tRNA brings amino acids to the ribosome Translation Termination 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) All mRNA’s start with AUG, so all DNA genes start with______? Answer •Methionine • 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 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. Mutation Lingo • Mutation = any change in nucleotide sequence of DNA • Reading frame = triplet grouping • Mutagenesis = creation of mutations 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 Chromosome Mutations Translocation • Inversion • has moved one segment of a chromosome to a different chromosome • Segment of a same chromosome is turned end to end 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:_______________________ ANSWER- • Substitution (C for the G) • Insertion (the C) • Deletion (the G) Chromosomal mutations Affect the entire chromosome often fatal. Mutagens can cut up DNA into pieces. When Repair mechanism reassembles them, they may be in the wrong order. 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 Viral Infections Viruses • Nothing more than packaged genes • Simple tools for geneticists • HIV EBOLA Bacteriophage Infection (SEM) Bacteriohage Infection Every virus has two stages • a dormant, particulate, transmissible stage called the virion stage • 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 Ebola Virus • Causes hemorrhagic fever • Movie Outbreak Hanta Virus • Southwestern US mice carried it cardiovascular collapse, respiratory failure, and death HIV • Has 2 copies of RNA • Is a retrovirus (RNA to DNA) • Carry enzyme reverse transcriptase Aids infected cells • HIV = Human Immunodeficiency Virus • AIDS = Acquired Immune Deficiency Syndrome 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 from one bacterial cell to another