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Chapter 12

Chapter 12. DNA and RNA. 12-1 DNA. What is a gene? A sequence of DNA that codes for a protein that determines a trait What is DNA? Deoxyribonucleic acid DNA is the chemical structure that makes up a gene. DNA discoveries. Griffith Studied pneumonia- harmless strain + harmful strain

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Chapter 12

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  1. Chapter 12 DNA and RNA

  2. 12-1 DNA • What is a gene? • A sequence of DNA that codes for a protein that determines a trait • What is DNA? • Deoxyribonucleic acid • DNA is the chemical structure that makes up a gene

  3. DNA discoveries • Griffith • Studied pneumonia- harmless strain + harmful strain • Killed harmful strain and mixed with harmless • Mice still got sick! • Conclusion: disease-causing ability was inherited • Transformation: process by which one strain of bacteria is changed by a gene or genes into another

  4. DNA discoveries • But HOW was it inherited? • Avery • Made extract (“juice”)from harmful bacteria • Treated it to kill certain macromolecules • Transformation still happened • Treated it to kill DNA • No transformation • Conclusion: nucleic acid (DNA!) responsible for transformation

  5. DNA discoveries • Hersheyand Chase • Studied viruses • Bacteriophage: virus that infects bacteria • Made up of protein coat and DNA • which carries genetic material? • Conclusion: DNA does!

  6. 4 Criteria for a gene: • 1. must be able to store info. and be able to carry it from one generation to the next • 2. must be strong and stable so it doesn’t break down • 3. must be easily copied • 4. must be able to mutate- variation allows for adaptation to occur

  7. DNA Structure • What are the monomers of nucleic acids? • Nucleotides • Nucleotides made up of 3 parts: • 5 C sugar • Phosphate group • Nitrogenous bases • Adenine (A) • Guanine (G) • Cytosine (C) • Thymine (T)

  8. Structural discoveries • Chargoff- base pairing • A = T and C = G • Rosalind Franklin- x-ray diffraction • showed “x” shape pattern • Watson and Crick • Double helix (“twisted ladder”) • H bonds between bases

  9. DNA origami! • http://www.yourgenome.org/teachers/origami.shtml

  10. 12-2 chromosomes and dna replication • Where is our DNA? • Eukaryotes- nucleus • multiple chromosomes • Prokaryotes- cytoplasm • usually 1 chromosome

  11. Dna structure • VERY long • Ex: E. Coli has 1 chromosome • Like fitting 300m of rope in a backpack • Nucleus of a human cell has ~1 meter of DNA • How does it fit?

  12. chromosome structure • Chromosomes made up of… • Chromatin: DNA coiled around protein (histones) • Form a nucleosome- continue folding DNA in nucleus (coils and supercoils)

  13. Dna replication • Replication: process by which a cell duplicates it’s DNA • WHY do we replicate DNA? • Mitosis • Meiosis

  14. Dna replication • Step 1: two strands separate • Enzyme helicase “unzips” the double helix • break H bonds • Creates 2 replication forks

  15. DNA Replication • Step 2: base pairing creates complimentary strands • Half old/half new • Enzyme DNA polymerasejoins individual nucleotides forming a polymer • proofreading

  16. DNA replication • http://www.youtube.com/watch?v=zdDkiRw1PdU

  17. 12-3 RNA and Protein synthesis • Gene: a sequence of DNA that codes for proteins that determine a trait • What does protein synthesis mean? • Making proteins! • “code” = nucleotide sequence • Must first turn DNA into RNA

  18. RNA • Ribonucleic acid • RNA Structure: • Single stranded • Ribose sugar • Phosphate group • Nitrogenous bases • Uracil in place of thymine (U in place of T)

  19. 3 Types of RNA • ALL involved in protein synthesis • 1. Messenger RNA (mRNA) • Carries copies of instructions to make proteins from DNA to rest of cell • 2. Ribosomal RNA (rRNA) • Make up ribosomes • 3. Transfer RNA (tRNA) • Transfers amino acids to ribosomes during protein synthesis

  20. Protein synthesis • Involves transcription and translation • Transcription: copying DNA sequence into RNA sequence • Translation: using mRNA to code for a protein

  21. transcription • DNA separated into 2 strands • RNA polymerase (enzyme)-uses each strand as a template to build complementary RNA strand • (similar to DNA polymerase) • Promoter region- specific sequence of bases that tells where to start building RNA strand

  22. Rna editing • RNA polymerase also proofreads + corrects mistakes • Exons: nucleotides that code for proteins • “express proteins” • Introns: nucleotides NOT involved in protein synthesis • These are “cut” out

  23. The genetic “code” • What are the monomers of proteins? • Amino acids! (aa) • RNA has 4 possible bases (A, U, C and G) • 3 bases = codon: code for a specific aa • aa are added together to make a protein polymer • “start” and “stop” codons

  24. translation • Ribosomes “read” the code for the protein • “Expression” • 1. mRNA attaches to ribosome • 2. codons code for an aa • tRNA brings aa to ribosome- add to chain • Peptide bonds • Anticodon- part oftRNA- complimentary to mRNA codon • 3. continue until “stop” codon

  25. translation

  26. Protein synthesis- summary

  27. Protein synthesis • http://www.youtube.com/watch?v=NJxobgkPEAo

  28. Roles of Dna and Rna • DNA: like a master plan • stay safe in the nucleus • RNA: like a blue print copy • disposable

  29. Genes and proteins • What does protein have to do with traits? • Genes: code for protein that determines a trait! • Proteins are microscopic tools that build parts of living things • What we look like • Many proteins are enzymes- catalyze chemical reactions • How we function

  30. Vocabulary quiz review • The type of RNA that carries instructions to make proteins from DNA to the rest of the cell • Messenger RNA (mRNA) • A sequence of DNA that codes for a protein that determines a trait • Gene • The type of protein that DNA coils around to make chromatin • Histone • The enzyme used to create the new strand of DNA during replication • DNA polymerase

  31. Vocabulary quiz review • A sequence of nucleotides that are involved in protein synthesis • Exon • A 3 base sequence of nucleotides that code for an amino acid • Codon • A 3 base sequence of nucleotides found on tRNA that are complimentary to a codon • Anticodon • A region of DNA that signals RNA polymerase to start building the RNA strand • Promoter region

  32. Vocabulary quiz review • This is the process of copying a DNA sequence into an RNA sequence • Transcription • This is the process of using mRNA to code for a protein • Translation • This is the process where one strain of bacteria is changed into another strain by altering a gene or genes • Transformation • The rule that, in DNA, cytosine can only bond to guanine and adenine can only bond to thymine • Complimentary base pairing

  33. 12-4 mutations • Mutations: changes in genetic material • Gene mutations: changes in single gene • Chromosomal mutations: changes in whole chromosomes

  34. Gene mutations • Point mutations: involve 1 or a few nucleotides • Effect 1 aa • Types: Substitutions, insertions, deletions • Frameshift mutations: a shift in the entire reading frame • Effects all aa • Protein may be unusable

  35. Chromosomal mutations • Types: • Deletion- loss of all/part of a chromosome • Duplication- extra copies of a chromosome • Inversion- reverse direction of the chromosome • Translocation- part of a chromosome breaks off and joins a different one

  36. Significance of mutations • Most are harmless/neutral • Some change proteins structure/expression- cause damage • Cancer and other disorders • Some are beneficial • Ex: polyploidy plants- have extra sets of chromosomes- are usually stronger

  37. 12-5 gene regulation • Genes are “turned on and off” as needed • Expression: when a gene is turned on, and the protein is coded for • Not all genes expressed at once • Prokaryotes and eukaryotes regulate differently

  38. Lac operon example • Prokaryote gene regulation • Operon: a group of genes working together • Regulatory sites (aka: operator): site where proteins bind to regulate transcription • Lac operon genes- used by E. coli to break down lactose for food • When lactose is present, gene turned “on” • When no lactose present, protein binds to operator, turning gene “off”

  39. Eukaryote gene regulation • More complex- usually no operons • TATA box- sequence of nucleotides tells RNA polymerase where to go and what to express • Only express what is needed

  40. Development and differentiation • Differentiation: when cells become specialized in structure and function • Hox genes controls differentiation in cells, starting in the embryo

  41. Hox gene manipulations • Hox genes can be manipulated • Ex: gene for antenna replaced with gene for leg • You get a leg on the fly’s face! • Common ancestry= ability to manipulate across species • Ex: gene for mouse eye + gene for fly leg = eye on fly’s leg

  42. REAl life gene regulation issue- teratoma • http://www.youtube.com/watch?v=jpk61xc8KF4

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