1 / 25

Chapters 12 and 13

Chapters 12 and 13. 0. DNA and Protein Synthesis. Discovery of the Role of DNA. A. 1928 - Frederick Griffith discovers transformation in bacteria : * discovered that “something” was able to transform harmless ( non – virulent ) bacteria into harmful ( virulent ).

hellis
Download Presentation

Chapters 12 and 13

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapters 12 and 13 0 DNA and Protein Synthesis

  2. Discovery of the Role of DNA A. 1928 - Frederick Griffith discovers transformation in bacteria : * discovered that “something” was able to transform harmless (non – virulent) bacteria into harmful (virulent)

  3. Discovery of the Role of DNA (cont’d) animation • 1944 -Oswald Avery and colleagues show that DNA can transform bacteria • 1952 - Alfred Hershey and Martha Chase use bacteriophage to confirm that DNA (not protein) is the genetic material

  4. Discovery of the Role of DNA (cont’d) D. 1953 - James Watson and Francis Crick propose a structural model for the DNA molecule Based On: X-Ray crystallographyimages prepared by Maurice Wilkins and Rosalind Franklin Chargaff’s Rule: # of Adenines = # of Thymines # Guanines = # of Cytosines

  5. DNA and RNA are Polymers of Nucleotides • Both are nucleic acids made of long chains of nucleotide monomers • A nucleotide (building block of a nucleic acid) has 3 parts: • A phosphate (PO4-) group that is negatively charged • A 5-Carbon sugar (deoxyribose in DNA or ribose in RNA) • A nitrogen-containing base

  6. Thymine, Cytosine, Adenine, and Guanine DNA (deoxyribonucleic acid) bases: purines pyrimidines • Pyrimidines: single ring bases • Purines: double ring bases • Complimentary bonding pattern: • Adenine + Thymine (share 2 hydrogen bonds) • Cytosine + Guanine (share 3 hydrogen bonds)

  7. RNA: ribonucleic acid Similar to DNA except: • Sugar in RNA = ribose • Base “uracil” instead of thymine • Single stranded Figure 10.2C, D

  8. Twist The Structure of DNA • Two polynucleotide strands wrapped around each other in a double helix • A sugar-phosphate backbone • Steps made of hydrogen-bound bases (A=T, C G)

  9. DNA REPLICATION: • Helicase enzyme splits H bonds between bases… unzips a portion of DNA • DNA polymerase binds to each strand • DNA polymerase adds complimentary nucleotides to each parent strand • Replication continues until both parent strands are copied • DNA polymerase “proof-reads” molecule for mistakes replication fork: location where DNA helix is still together. Next place to be unzipped replication bubble: location where DNA is being copied

  10. Each strand of the double helix is oriented in the opposite direction (“anti-parallel”) “prime” #’s refer to carbons in the sugar At one end, the 3’ carbon has an (OH) and at the opposite, a 5’ carbon has the PO4- Why does this matter? DNA polymerase can only add nucleotides to the 3’ end. A daughter strand can only grow from 5’  3’ Therefore, only one daughter strand is made continuously (leading strand) The other strand (lagging strand) is made in a series of short pieces (Okazaki fragments), later connected by DNA ligase Bioflix movie A Structural Problem with DNA Replication

  11. Replication in Living Cells: Prokaryote v. Eukaryote Prokaryote: * one single loop of DNA * regulatory proteins bind to a starting point on the 1 chromosome * bi-directional replication until all is copied • Eukaryote: • much more DNA to copy • replication begins at many points, bi-directional replication • after replication is finished, replicated chromatin threads condense into chromosomes

  12. When DNA can repair mistakes and when it can’t DNA enzymes work like a spell checker • Cut out wrong sequences • Undamaged strand is template • Only 2 or 3 stable changes per year Mutations: some severe, others are not • Inheritable changes occur in gametogenesis • Now the “wrong” sequences are copied • Ex: cystic fibrosis (CF): a deletion of 3 nucleotides in a certain gene • Ex: sickle cell anemia: one nucleotide substitution in the hemoglobin gene • Mutagen: a mutation causing substance (can break DNA) • Ex: x-rays, radioactivity, nicotine

  13. Protein Synthesis: the transfer of information from: DNA  RNA  Proteins “gene expression”: A gene is a linear sequence of many nucleotides. 3 Types: • Structural genes: have info to make proteins • Regulatory genes: code for proteins which are on/off switches for other genes • Genes that code for tRNA, rRNA, histones DNA vs. RNA • single stranded • A U C G • ribose sugar • 3 types of RNA: • messenger, transfer, ribosomal • double stranded • A T C G • deoxyribose sugar mRNA (messenger):copies DNA’s message in nucleus  brings it to cytoplasm tRNA (transfer):carries amino acids to mRNA so protein can be made rRNA (ribosomal): major part of the ribosome. Helps link amino acids from tRNA’s together  assemble protein

  14. Protein Synthesis is Two Steps: • Transcription: The DNA of the gene is transcribed into mRNA • Translation: decoding the mRNA and assembling the protein

  15. 1. Transcription: Eukaryote • DNA sequence (message for protein) is transcribed by mRNA • Only one strand (bottom; non-coding strand) is needed as a template Steps: RNA polymerase splits H bonds in DNA section RNA polymerase attaches to a promoter region on DNA to begin transcription RNA polymerase travels along bottom strand of DNA. RNA nucleotides join in a complimentary pattern (A=U, C=G) A termination signal reached, transcription over mRNA strip detaches from DNA, DNA helix closes up mRNA is processed: Intronsare cut out, Exonsare glued together, cap and tail are added. Mature mRNA leaves nucleus through pores cytoplasm for next step (translation)

  16. 2. Translation: the synthesis of proteins using mRNA, tRNA and ribosomes • The Genetic Code: the language in which instructions for proteins are written in the nucleotide sequences • Each triplet of mRNA nucleotides is a “codon” because it will “code” for 1 amino acid • Ex: AUG GUC CCU AAU CCU Met – Val – Pro – Asn – Pro • Original strand of DNA (coding strand): ATG GTC CCT AAT CCT • Only difference: U is substituted for T • Use the Genetic Codechart to “decode” mRNA message

  17. The Genetic Code is the Rosetta Stone of Life • Nearly all organisms use exactly the same genetic code • More than one codon for most amino acids = degenerate nature…a change (mutation) in gene does not always mean a different amino acid. • what does CAU code for? ACU? UAU? GCC? • how many codons for Leu? • what is special about AUG and it’s amino acid, Methionine? • what is special about UAA, UAG, and UGA? HIStidine…THReonine…TYRosine…ALAnine

  18. An exercise in translating the genetic code: Step 1: fill in corresponding DNA bases to dark blue strand (non-coding) Step 2: Transcribe the dark blue strand into mRNA (pink) Step 3: Translate the codons into correct amino acids (use chart) G A A A T G T G T T T A Coding strand (gene we want copied) transcription translation

  19. An exercise in translating the genetic code: answers Step 1: fill in corresponding DNA bases to dark blue strand (non-coding) Step 2: Transcribe the dark blue strand into mRNA (pink) Step 3: Translate the codons into correct amino acids (use chart)

  20. How Does Translation Happen? Need: tRNAs and ribosomes (rRNA) tRNA: single stranded RNA, folded up * 2 parts: anticodon and aa attachment site • Ribosome: 2 protein subunits and ribosomal RNA * allows aa’s to attach by making peptide bonds * travels along mRNA strip, tRNA’s join and bring correct amino acids • Confused? • Watch demo on board and videos animation bioflix animation

  21. Put It All Together:

  22. Mutations can change the message of genes • Mutations: • changes in DNA base sequence • caused by errors in DNA replication, recombination, or by mutagens • substituting, inserting, or deleting nucleotides also alters a gene “point mutation”…may or may not alter amino acid sequence “frame-shift mutation”…most devastating to protein structure

  23. Chromosomal Mutations: • affect chromosome structure and shape • can occur during crossing over (prophase 1) • 4 types: deletion, duplication, inversion, translocation • Genetic Mutations: Harmful of helpful? • can be both • depends on environment • Harmful Examples: • a) defective proteins from defective genes can disrupt normal cell function (ex: regulation of cell cycle  cancer) • b) sickle cell anemia (one point mutation in hemoglobin gene). Cells form sickle shape, can’t carry oxygen, can block blood vessels, painful. • Helpful Examples: • new proteins made by mutations can give an advantage in a certain environment • ex: antibiotic resistant bacteria, peppered moths

  24. Please make the following changes: On multiple choice section 2: #7 “A” + “C” Cross out: “the growing molecule” PUT IN: “the parent strand”

More Related