Chapter 7 DNA Structure and Gene Function

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1 Chapter 7 DNA Structure and Gene Function DNA bursting from bacterial cell Dr. Gopal Murti/Science Source Copyright McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

2 What is DNA? DNA stored information for protein production. DNA (genotype) RNA Protein (phenotype) Section 7.1

3 Rosalind Franklin

4 Watson & Crick

5 Double-stranded DNA Histones Chromatin material: not visible during Interphase One chromatid Its sister chromatid Centromere Chromosome: visible during mitosis Figure 17.2

6 DNA Review Figure 2.24 DNA Nucleotide Deoxyribose sugar Phosphate group Nitrogenous base A, G, C, T Base pair Phosphate Sugar Nucleotide

7 DNA Structure Sugars & phosphates Nitrogenous Bases

8 DNA Base Pair Rules (Chargaff s Rules) DNA Base Pairing

9 DNA Is a Double Helix Hydrogen bonds connect complementary DNA strands. Hydrogen bonds Section 7.1 Figure 7.5

10 RNA Review RNA Nucleotide Ribose sugar Phosphate group Nitrogenous base A, G, C, U

11 Review: DNA & RNA Comparison Section 7.3 Figure 7.9

12 Nitrogenous Bases 1. Which nitrogenous base is only found in RNA? uracil 2. Which nitrogenous base is only found in DNA? thymine 3. Which nitrogenous bases are found in both DNA & RNA? adenine/guanine/cytosine

13 What is the main function of DNA? A. encode proteins B. produce ATP C. speed up cell reactions D. provide structural support to the cell E. All of the choices are correct. Flower: Doug Sherman/Geofile/RF

14 Protein Synthesis Prokaryotic cells Transcription DNA RNA Translation RNA proteins

15 Protein Synthesis Eukaryotic cells Transcription DNA RNA RNA Processing Modify pre-mrna Translation RNA proteins

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17 Genetic Code Codon mrna

18 Fig (a) Tobacco plant expressing a firefly gene (b) Pig expressing a jellyfish gene

19 Protein Production Starts with DNA Transcription: DNA RNA 3 types of RNA Translation: RNA Protein Section 7.3 Figure 7.8

20 Fig. 17-1

21 Protein Production Starts with DNA Protein analogy Cooking Section 7.3 Figure 7.8 Modification to ingredients?

22 Transcription Uses DNA to Create RNA How does DNA pair with RNA? Section 7.4 Figures 7.8, 7.9

23 Fig Promoter Transcription unit Transcription Overview 5 3 Start point RNA polymerase DNA 1 Initiation 3 5 Elongation Nontemplate strand of DNA 5 3 Unwound DNA RNA transcript Template strand of DNA 2 Elongation RNA polymerase 3 end RNA nucleotides Rewound DNA 5 RNA transcript Termination Completed RNA transcript Newly made RNA Direction of transcription ( downstream ) Template strand of DNA

24 Transcription Uses DNA to Create RNA Initiation Initiation RNA polymerase enzyme DNA RNA polymerase binds to the promoter region Promoter DNA template strand Section 7.4 Figure 7.10

25 Transcription Uses DNA to Create RNA Elongation Elongation RNA polymerase DNA RNA complementary to DNA RNA Section 7.4 Figure 7.10

26 Transcription Uses DNA to Create RNA Termination Termination RNA polymerase RNA, DNA, and RNA polymerase separate. DNA DNA becomes a double helix again. RNA Terminator Section 7.4 Figure 7.10

27 Transcription Uses DNA to Create RNA Termination Termination RNA polymerase The cell produced an RNA copy of a gene! DNA RNA Terminator Section 7.4 Figure 7.10

28 Fig Promoter Transcription unit Transcription Overview 5 3 Start point RNA polymerase DNA 1 Initiation 3 5 Elongation Nontemplate strand of DNA 5 3 Unwound DNA RNA transcript Template strand of DNA 2 Elongation RNA polymerase 3 end RNA nucleotides Rewound DNA 5 RNA transcript Termination Completed RNA transcript Newly made RNA Direction of transcription ( downstream ) Template strand of DNA

29 If DNA reads 5' - TACTTCAAAATC - 3 What are the transcribed RNA bases? How many codons? How many amino acids will be present after translation?

30 RNA Is Processed in the Nucleus Poly A tail and mrna cap are added to the RNA. Section 7.4 Figure 7.11

31 RNA Is Processed in the Nucleus Introns Introns are removed from the RNA molecule. Exons Section 7.4 Figure 7.11

32 RNA Is Processed in the Nucleus The RNA then leaves the nucleus. Onward to translation! Section 7.4 Figure 7.11

33 Fig Alternative Splicing Exons DNA Troponin T gene Primary RNA transcript RNA splicing mrna or

34 If the DNA template strand has the following sequence, what would be the nucleotide sequence of the complementary RNA molecule produced in transcription? Template strand: AGTCTT A. AGTCTT B. AGUCUU C. TCAGAA D. TCUGUU E. UCAGAA Flower: Doug Sherman/Geofile/RF

35 7.4 Mastering Concepts How is mrna modified before it leaves the nucleus of a eukaryotic cell? DNA bursting from bacterial cell Dr. Gopal Murti/Science Source

36 Translation Builds the Protein Now let s look at how a ribosome uses RNA to produce a protein. Section 7.5 Figure 7.8

37 Translation Builds the Protein DNA DNA template strand TRANSCRIPTION T T C A G T C A G A A G U C A G U C mrna Codon Codon Codon TRANSLATION Lysine Serine Valine Protein Polypeptide (amino acid sequence) A codon is a three-nucleotide sequence that encodes one amino acid. Section 7.5 Figure 7.12

38 First letter of codon Translation Builds the Protein mrna TRANSLATION Protein A A G U C A G U C Codon Codon Codon Lysine Serine Valine Polypeptide (amino acid sequence) The genetic code shows which mrna codons correspond to which amino acids. The Genetic Code Second letter of codon U C A G U UUU UUC UUA UUG Phenylalanine (Phe; F) Leucine (Leu; L) UCU UCC UCA UCG Serine (Ser; S) UAU UAC UAA UAG Tyrosine (Tyr; Y) Stop Stop UGU UGC UGA UGG Cysteine (Cys; C) Stop Tryptophan (Trp; W) U C A G C A CUU CUC Leucine (Leu; L) CUA CUG AUU AUC Isoleucine (Ile; I) AUA AUG Start Methionine (Met; M) CCU CCC CCA CCG ACU ACC ACA ACG Proline (Pro; P) Proline (Pro; P) CAU CAC CAA CAG AAU AAC AAA AAG Histidine (His; H) Glutamine (Gln; Q) Asparagine (Asn; N) Lysine (Lys; K) CGU CGC CGA CGG AGU AGC AGA AGG Arginine (Arg; R) Serine (Ser; S) Arginine (Arg; R) U C A G U C A G Third letter of codon G GUU GUC GUA GUG Valine (Val; V) GCU GCC GCA GCG Proline (Pro; P) GAU GAC GAA GAG Aspartic acid (Asp; D) Glutamic acid (Glu; E) GGU GGC GGA GGG Glysine (Gly; G) U C A G Section 7.5 Figure 7.12

39 Translation Cast members of Protein Synthesis mrna Translation Builds the Protein

40 Transfer RNA (trna) translate the genetic code. Translation Cast members of Protein Synthesis Translation Builds the Protein Section 7.5 trna: Tom Pantages/Phototake Figure 7.13

41 Translation Cast members of Protein Synthesis Ribosome Large subunit P site A site Small subunit Translation Builds the Protein

42 Translation Protein Synthesis Initiation 1. Binding of mrna, 1 st trna w/ aa and small ribosome 2. Binding of the large subunit Translation Builds the Protein

43 Translation Protein Synthesis Elongation Codon recognition Type of bond? Peptide bond formation trna in P-site leaves trna in A-site has protein translocation Translation Builds the Protein

44 Translation Protein Synthesis Termination

45 Polyribosomes

46 Translation Builds the Protein Translation is efficient when multiple ribosomes attach to an mrna molecule simultaneously. mrna Ribosome Polypeptide SEM (false color) 50 nm Section 7.5 Ribosomes: Kiseleva and Donald Fawcett/Visuals Unlimited Figure 7.16

47 Fig Secretory proteins endomembrane system Ribosome mrna Signal peptide Signalrecognition particle (SRP) CYTOSOL ER LUMEN SRP receptor protein Translocation complex Signal peptide removed ER membrane Protein Protein Synthesis

48 Amino acid trna UAC anticodon mrna codon DNA

49 Mutations Change DNA A mutation is a change in a cell s DNA sequence. Mutations come in several varieties. Section 7.7 Wild fly: Andrew Syred/Science Source; Mutant fly: Science VU/Dr. F. R. Turner/Visuals Unlimited Figure 7.20

50 Mutations Change DNA A point mutation changes one or a few base pairs in a gene. Section 7.7 Table 7.2

51 Normal red blood cells Mutations Change DNA G G A C T C C T T C C U G A G G A A No aggregation of hemoglobin molecules Point Mutation - Substitution Pro Glu Glu SEM 6 µm Sickled red blood cells G G A C A C C T T C C U G U G G A A Abnormal aggregation of hemoglobin molecules Section 7.7 Pro Val Glu SEM 6 µm Normal cells: Micro Discovery/Corbis; Sickled cells: Dr. Gopal Murti/Science Source Figure 7.21

52 Mutations Change DNA Wildtype = original nucleotide sequence Substitution = changed nucleotide(s) In lab 1 base change Salt instead of sugar Silent mutation? Section 7.7 Table 7.2

53 Mutations Change DNA Frameshift mutations affect multiple codons. Insertion of one nucleotide changes every codon after the insertion. Section 7.7 Table 7.2

54 Figure 10.16B Normal gene mrna Protein A U G A A G U U U G G C G C A Met Lys Phe Gly Ala Nucleotide substitution A U G A A Met Lys G U U U Phe A G C G C A Ser Ala Frameshift Mutations U Deleted Nucleotide deletion A U G A A G U U G G C G C A U Met Lys Leu Ala His Inserted Nucleotide insertion A U G A A G U U G U G G C G C Met Lys Leu Ala His

55 Mutations Change DNA Section 7.7 Figure 7.22

56 But mutations are not always harmful! Mutations Change DNA Mutations create different versions of genes Alleles alternative versions of the same gene Genetic variation is important for evolution. What determines if a mutation is advantageous or not? Grapefruit: Erich Schlegel/Dallas Morning News/Corbis; rice: Pallava Bagla/Corbis; cotton: Scott Section 7.7 Olson/Getty Images Figure 7.23

57 Chapter 8 DNA Replication, Binary Fission, and Mitosis World s tallest man Frederic J. Brown/AFP/Getty Images Copyright McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

58 Two Types of Cell Division Interact in the Sexual Life Cycle Sex cells combine at fertilization. Section 8.1 Figure 8.1

59 Mitosis Has Many Roles 1) Grow and develop 2) repair tissues 3) regenerate lost body parts 4) Some organisms reproduce asexually by mitosis Section 8.1

60 Mitosis Has Many Roles Mitosis produces the cells that build the human body. Day 1 zygote: Pascal Goetgheluck/Science Source Section 8.1 Figure 8.2 Day 2, 3 zygote: Richard G. Rawlins, Ph.D./ Custom Medical Stock Photo Middle and bottom row photos: Bradley R. Smith, Ph.D.

61 Cell Death Is Part of Life Apoptosis, or cell death, carves out distinctive structures. Section 8.1 Duckling: GK hart/vikki Hart/Getty Images RF Figure 8.3

62 Mitosis and Apoptosis Work Together Mitosis adds new cells while apoptosis removes them, allowing tissues to renew themselves. Section 8.1

63 Shortly after fertilization, a zygote divides into two identical cells. What type of cell division produces these two cells? A. mitotic cell division B. meiotic cell division C. apoptosis Flower: Doug Sherman/Geofile/RF

64 DNA Replication Precedes Cell Division For each of the daughter cells from this division to have identical DNA, the cell must first replicate its genome, all of the cell s genetic material. Section 8.2 Tumor cells: Steve Gschmeissner/SPL/Getty Images RF

65 Cell Cycle Mitosis Nucleus divides Cytokinesis Cell divides Interphase Mitotic phase (karyokinesis) Prophase Metaphase Anaphase Telophase Cytokinesis G 2 G 1 Cell prepares for division. Growth continues slowly. M Primary period of cell growth. S DNA is duplicated. Growth continues slowly. G 0 Figure 17.1

66 DNA Replication When does DNA replication take place? Why does DNA replication take place?

67 Centromere DNA Replication Overview

68 Keys: = Cytosine = Adenine = Guanine = Thymine Replication bubble Parent DNA molecule 2 complete daughter DNA molecules Parent strands New complementary strands b) The unwinding and the formation of new strands occur simultaneously at many sites on the DNA molecule. The sites of replication expand outward until they join. For simplicity the two strands are shown as parallel in (b), but in actuality they form a helical shape as shown in (a). Why many origins of replication? Parent strand New (daughter) strands forming Parent strand a) The double-stranded DNA unwinds, and each single strand serves as a template for a new complementary strand. Figure 17.4

69 DNA Replication Enzymes 1. Helicase 2. Single strand binding protein 3. Primase 4. DNA polymerase 5. DNA ligase 1. Looks for start points Opens DNA 2. Helps keep DNA opened 3. Primes DNA replication 10 RNA nucleotides 4. a) Copies DNA b) converts RNA nucleotides to DNA nucleotides c) proofreads d) corrects errors 5. Joins DNA sections (fragments)

70 DNA Replication Precedes Cell Division Semi conservative: ½ old & ½ new Section 8.2 Figure 8.6

71 DNA Replication Precedes Cell Division 1) Helicases 2) Binding proteins Section 8.2 Figure 8.5

72 DNA Replication Precedes Cell Division 3) Primase Section 8.2 Figure 8.5

73 Priming for DNA Replication Primase RNA primer

74 DNA Replication Precedes Cell Division 4) DNA polymerase New strand 5 3 Section 8.2 Figure 8.5

75 DNA Elongation

76 Replication Fork

77 DNA Replication Precedes Cell Division Leading Strand: synthesis is continuous. Section 8.2 Figure 8.5

78 Leading & Lagging Strands

79 DNA Replication Precedes Cell Division Lagging Strand: opposite direction from helicase movement. Strand synthesis is discontinuous. Section 8.2 Figure 8.5

80 DNA Replication Precedes Cell Division 4) DNA polymerase RNA primer with DNA 5) Ligases Section 8.2 Figure 8.5

81 DNA Replication Precedes Cell Division Semi conservative: ½ old & ½ new Section 8.2 Figure 8.6

82 DNA Replication Enzymes 1. Helicase 2. Single strand binding protein 3. Primase 4. DNA polymerase 5. DNA ligase 1. Looks for start points Opens DNA 2. Helps keep DNA opened 3. Primes DNA replication 10 RNA nucleotides 4. a) Copies DNA b) converts RNA nucleotides to DNA nucleotides c) proofreads d) corrects errors 5. Joins DNA sections (fragments)

83 Figure 10.22A Prokaryotic Genetic Diversity Horizontal Gene Transfer increases bacterial diversity 1. Transformation DNA enters cell A fragment of DNA from another bacterial cell Bacterial chromosome (DNA)

84 Figure 10.22B Horizontal Gene Transfer 2. Transduction Phage A fragment of DNA from another bacterial cell (former phage host)

85 Figure 10.22C Horizontal Gene Transfer 3. Conjugation Mating bridge Sex pili Donor cell Recipient cell

86 Figure 10.22D Horizontal Gene Transfer 3. Conjugation Donated DNA Crossovers Degraded DNA Recipient cell s chromosome Recombinant chromosome

87 Figure 10.20A HIV Envelope Glycoprotein Protein coat RNA (two identical strands) Reverse transcriptase (two copies)

88 HIV & Protein Synthesis

89 Figure 10.18_UN Mumps Virus MMR vaccine (measles, mumps & rubella) Polio

90 Figure Viral RNA (genome) Glycoprotein spike Protein coat Membranous envelope Plasma membrane of host cell 1 Entry CYTOPLASM Viral RNA (genome) 2 3 Uncoating RNA synthesis by viral enzyme 4 mrna Protein synthesis 5 RNA synthesis (other strand) Template New viral proteins 6 Assembly New viral genome 7 Exit

91 Figure Emerging Viruses HIV, West Nile Virus, SARS, H1N1 swine flu How do they come arise? Mutations Contact btn species Spread from isolated populations

92 Figure 10.UN03 DNA is a polymer made from monomers called (a) (b) is performed by an enzyme called (c) (d) RNA comes in three kinds called (e) (f) molecules are components of (g) use amino-acid-bearing molecules called is performed by structures called (h) Protein one or more polymers made from monomers called (i)