1. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero Chapters 12 and 13 DNA and Protein Synthesis

2. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings A. 1928 - Frederick Griffith discovers transformation in bacteria : * discovered that “something” was able to transform harmless (non – virulent) bacteria into harmful (virulent) Discovery of the Role of DNA

3. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings B.1944 -Oswald Avery and colleagues show that DNA can transform bacteria C.1952 - Alfred Hershey and Martha Chase use bacteriophage to confirm that DNA (not protein) is the genetic material Discovery of the Role of DNA (cont’d) animation

4. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings D. 1953 - James Watson and Francis Crick propose a structural model for the DNA molecule Discovery of the Role of DNA (cont’d) 1. X-Ray crystallography images prepared by Maurice Wilkins and Rosalind Franklin 2.Chargaff’s Rule: # of Adenines = # of Thymines # Guanines = # of Cytosines Based On:

5. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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: 1.A phosphate (PO 4 - ) group that is negatively charged 2.A 5-Carbon sugar (deoxyribose in DNA or ribose in RNA) 3.A nitrogen-containing base

6. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings DNA (deoxyribonucleic acid) bases: Pyrimidines: single ring bases Purines: double ring bases Complimentary bonding pattern: Adenine + Thymine (share 2 hydrogen bonds) Cytosine + Guanine (share 3 hydrogen bonds) Thymine, Cytosine, Adenine, and Guanine pyrimidines purines

7. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Similar to DNA except: Sugar in RNA = ribose Base “uracil” instead of thymine Single stranded Figure 10.2C, D RNA: ribonucleic acid

8. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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) Twist

9. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings DNA REPLICATION: 1.Helicase enzyme splits H bonds between bases… unzips a portion of DNA 2.DNA polymerase binds to each strand 3.DNA polymerase adds complimentary nucleotides to each parent strand 4.Replication continues until both parent strands are copied 5.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. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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 PO 4 - 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. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Protein Synthesis: the transfer of information from: DNA  RNA  Proteins “gene expression”: A gene is a linear sequence of many nucleotides. 3 Types: 1.Structural genes: have info to make proteins 2.Regulatory genes: code for proteins which are on/off switches for other genes 3.Genes that code for tRNA, rRNA, histones double stranded A T C G deoxyribose sugar single stranded A U C G ribose sugar 3 types of RNA: messenger, transfer, ribosomal DNA vs. RNA 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. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 1.Transcription: The DNA of the gene is transcribed into mRNA 2.Translation: decoding the mRNA and assembling the protein Protein Synthesis is Two Steps:

15. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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: 1.RNA polymerase splits H bonds in DNA section 2.RNA polymerase attaches to a promoter region on DNA to begin transcription 3.RNA polymerase travels along bottom strand of DNA. RNA nucleotides join in a complimentary pattern (A=U, C=G) 4.A termination signal reached, transcription over 5.mRNA strip detaches from DNA, DNA helix closes up 6.mRNA is processed: Introns are cut out, Exons are glued together, cap and tail are added. 7.Mature mRNA leaves nucleus through pores  cytoplasm for next step (translation)

16. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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 Code chart to “decode” mRNA message

17. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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? The Genetic Code is the Rosetta Stone of Life HIStidine…THReonine…TYRosine…ALAnine

18. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings An exercise in translating the genetic code: A AG T A G TTTA GT 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) Coding strand (gene we want copied) transcription translation

19. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Need: tRNAs and ribosomes (rRNA) tRNA: single stranded RNA, folded up * 2 parts: anticodon and aa attachment site How Does Translation Happen? 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. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Put It All Together:

22. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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 “frame-shift mutation”…most devastating to protein structure “point mutation”…may or may not alter amino acid sequence

23. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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: a)new proteins made by mutations can give an advantage in a certain environment ex: antibiotic resistant bacteria, peppered moths

24. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

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