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Protein Synthesis From DNA to protein And viruses BIG PICTURE • Processing of Gene Information Prokaryotes versus Eukaryotes • Transcription and Translation Beadle and Tatum George Beadle and Edward Tatum during the late 1930s and early 1940s • Using Neurospora crassa bread mold determined "one gene one enzyme hypothesis" •has since been modified to "one gene one polypeptide" Protein Synthesis Overview Learn these Terms • Transcription = DNA → mRNA • Translation = mRNA → protein Three Bases Lingo • DNA Triplet ATC • mRNA Codon UAG Anti-codon AUC tRNA Three Bases Lingo • DNA original template • mRNA codes from DNA, takes to cytoplasm tRNA brings amino acid to ribosomes rRNA structure of ribosome Transcription • DNA never leaves the nucleus • It codes to mRNA to take the message outside the nucleus • What do you see? • Transcription Animation (HOT!!) Protein Synthesis Animation TeacherTube Videos –Protein Synthesis (good and to the point) TeacherTube Videos - DNA to Protein Introns and Exons • Primary mRNA = exons + introns • INTRONS (noncoding region of mRNA) are discarded • The coding regions, spliced together RNA are called EXONS. = Mature mRNA SPLICING ANIMATION • Spicing Animation from NobelPrize.org Click on: Schematic animation of mutually exclusive exons» • Before the mRNA leaves the nucleus, the introns are removed, and the exons are spliced together. • How Spliceosomes Process RNA Intron and Exon Summary TRANSLATION • mRNA (genetic language) needs to be translated into protein language • VCAC: Molecular Processes: Translation: The Movie TRANSLATION • Coding from mRNA to making protein • Animations (click here for translation animation) • Transcribe and Translate a Gene (good activity) 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 •Ribosome “reads” each codon (3 bases) on the mRNA. • The mRNA “chart” is consulted and the correct amino acid is determined. •What amino acids are being requested? ANSWER AGC =cysteine UGA =STOP CCU=proline AGC =serine GGA=glycine CAA=glutamine 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 ANIMATION: acid Animation of Translation •A tRNA with the anticodon complementary to the codon is sent to pick up the requested amino acid and bring it to the ribosome. tRNA’s hang out in the cytoplasm. Think of them as trucks that transport amino acids from where they float around in the cytoplasm, to the ribosome. Think of the anticodon as the license plate on the tRNAthat matches the mRNA codon. APE slots on the ribosome • The ribosome attaches to the mRNA and provides a slot (A) for the tRNA to slide into so it can match the mRNA. Note the P and A site • Protein Synthesis: Translation • A site – Amino acid is dropped off • P site – Polypeptide builds • E site-polypeptide exits There are 20 Amino Acids • These 20 are shared by all living organisms Notice AUG codon means “start” building a new protein. UAA, UAG, UGA mean “stop’ building the protein. All mRNA’s start with AUG, so all DNA genes start with______? Answer •Methionine Nice Animations of Protein Synthesis • Shows Nucleus to Protein • ☺Protein Synthesis Animation • Protein Synthesis Learning Activity - Flash Player Installation • 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 Examples of mutagens? GOOD OR BAD? Mutagen =any source of mutation is a physical or chemical agent –EX: X-rays –UV light –cigarette components –Hazardous chemicals Mutation Lingo • Mutation = any change in the genetic material (nucleotide sequence of DNA) Gene (point)mutations SUBSTITUTION – Replace one base for another. Minimal effect ADDITION – Adding a base DELETION – removing a base •Frameshift mutations =change every amino acid that follows the point of mutation 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 Frameshift • Animation Quiz 5 - Addition and Deletion Mutations Translocation Mutation Animations • What change do you notice? Translocation 9 and 22 Name the mutation • Animation Quiz 1 • (Not for the faint of heart) Human Mutants: Mutant Human Organs : Video : Discovery Channel Channel Also could have substitution 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 the G) AAGGTCTCGGAGT:____________________ Insertion (the C) AAGGTTCGAGT:_______________________ 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 NEWS FLASH!!!! • Not every gene in your body is translated into polypeptides all the time. OPERON • A cluster of genes under the control of a promoter (beginning of gene) Promoter • a nucleotide sequence that enables a gene to be transcribed Operator • a segment of DNA that a repressor or activator binds to Lac Operon (promoter and repressor) • Animation Quiz - The Tryptophan Repressor LAC OPERON (start making lactase) • The lac Operon ANIMATION • (If lactose is present, the repressor attaches to it. The genes to break down the lactose (lactase) can be made.) • PICK ME VCAC: Molecular Processes: Lac Operon: The Movie HOX Genes • Hox genes are defined by a DNA sequence known as the homeobox, which is a sequence of 180 nucleotides HOX GENES • “Body Plan Genes” HOX GENES: TELL THE BODY WHERE TO PUT THE PARTS 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