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DNA, RNA, and Protein Synthesis

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DNA, RNA, and Protein Synthesis Chapter 12 and 13 chap 12 notes * – PowerPoint PPT presentation

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Title: DNA, RNA, and Protein Synthesis


1
DNA, RNA, and Protein Synthesis
  • Chapter 12 and 13

2
Chap 12 Terms
  • Transformation
  • Bacteriophage
  • Base pairing
  • Nucleotides
  • Nucleic acids
  • Nitrogenous bases
  • Antparallel strands
  • Replication
  • Replication fork
  • DNA Polymerase
  • Helicase
  • Telomease
  • Ligase
  • Semi conservative

3
Do you know?
  • What determines how a protein will function?
  • three-dimensional shape of the protein
  • Why is it important that new cells have same DNA
    as the parent cell?
  • the cells may develop properties that would not
    be beneficial to the organism as a whole

4
Objectives??
  • Relate how Griffiths bacterial experiments
    showed that a hereditary factor was involved in
    transformation
  • Summarize how Averys experiments led his group
    to conclude that DNA is responsible for
    transformation in bacteria
  • Describe how Hershey and Chases experiments led
    to the conclusion that DNA, not protein, is the
    hereditary molecules in viruses

5
Discovery of DNA
  • From his studies with pea plants, Mendel
    concluded that hereditary factors determine many
    of an organisms traits. But what were these
    hereditary factors? How did these molecules store
    hereditary information? Scientists believed that
    if they could answer these questions, they could
    und4erstand how cell pass on characteristics to
    their descendants. The answers these questions
    began to emerge during an epidemic of pneumonia
    in London in the 1920s.

6
Experiments
  • Three experiments that led to the discovery of
    DNA and RNA
  • 1. Griffiths
  • 2. Averys
  • 3. Hershey-Chase experiments
  • Studies involved bacteria (bacteriophages or
    phages) and viruses (DNA head, protein body)

7
Griffiths experiments
  • 1928- studied bacteria Streptococcus pneumoniae
    (pneumonia)
  • Trying to develop a vaccine against virulent
    strain (disease-causing)
  • Virulent bacterium is surrounded by a capsule
    made of polysaccharides that protect it from a
    body's defense systems

8
Griffiths exp cont
  • Two strains of bacteria
  • 1. S strain smooth-edged colonies, ill
  • 2. R stain- rough colonies, lacks a capsule,
    does not cause pneumonia
  • Had a series of 4 exp fig 10-2 (BIO)
  • R cells ? mouse alive
  • S cells ? mouse dies
  • Kills S cells with heat ? mouse lives
  • Kills S cells with heat and mix with R cells?
    mouse dies (transformation occurs)

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Griffiths exp cont
  • Results or conclusion
  • Heat-killed virulent bacterial cells release a
    hereditary factor that transfers the disease-
    causing the healthy cells to be harmful
  • The transfer of genetic material from one cell
    to another is called transformation
  • (holt video)

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12
Heat Factor?
  • DNA can tolerate temperature near 90C without
    being altered. Proteins are denatured (broken
    down) at about 60C.
  • What effect temperature had on Griffiths works?
  • A The DNA was not altered and became
    incorporated into the DNA of the living bacteria

13
DNA Technology
  • Griffith manipulated genes with out knowing it.
    Today this manipulation of genes is known as
    genetic engineering or recombinant DNA
    Technology.
  • Transformation is a modern-day genetic
    engineering technique.
  • Examples bacteria used to introduce foreign
    genes into plant cells, producing plants with
    desirable traits (Genetic modified)

14
Avery's Experiments
  • 1940s wanted to test whether the transforming
    agent in Griffiths exp was protein, RNA, DNA
  • Used enzymes separately to id which part
  • Results
  • Cells missing protein and RNA able to transform R
    cells into s cells ? mice die
  • Cells missing DNA did not transform? mice lived
  • DNA is responsible for transformation in bacteria

15
Radioactivity review?
  • Radioactive elements have unstable nuclei that
    emit alpha and beta particles or energy as gamma
    rays.
  • Emissions make it easier for scientists to detect
    and trace the path of the radioactive elements as
    they interact with other materials or transformed
    during metabolic processes
  • (Radioactive isotopes, increase neutrons, and
    the mass of the element)

16
Hershey-Chase Experiment
  • ?They wanted to know if DNA or Protein was the
    hereditary material viruses transfer when viruses
    enter a bacterium
  • Bacteriophages or phages are viruses that infect
    bacteria (Holt video)
  • EXP
  • Used radioactive isotope sulfur (35S) to label
    protein and radioactive isotope phosphorus
    (32P)to label DNA
  • Infected the cells
  • Blended? separated the phage from bacteria
  • Results
  • Viral DNA and little protein entered bacteria ?
    concluded that DNA is the hereditary molecule in
    the viruses
  • (Honors 10.A)

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20
Key Questions
  • Evaluate the contributions of Franklin and
    Wilkins in helping Watson and crick discover
    DNAs double helix structures
  • Describe the 3 parts of a nucleotide
  • Summarize the role of covalent and hydrogen bonds
    in the structure of DNA
  • Relate the role of the base-paring rules to the
    structure of DNA

21
DNA
  • By the early 1950s, most biologist accepted DNA
    as the hereditary material. However, they still
    lacked an understanding of DNAs structure or how
    this molecule could replicate, store, and
    transmit hereditary information and direct cell
    function. These mysteries would soon begin to
    unravel at Cambridge university in England.

22
DNA is a double-stranded Helix
  • Pauling, Wilkins, Franklin- were first
  • They used x-ray diffraction
  • Watson saw an x-ray produced by Franklin and was
    able to figure out the basic shape of DNA to be a
    helix (fig 10-5 bio)
  • Watson and Crick began trying to construct a
    double helix w/ uniform diameter that would
    confirm Franklins data
  • 1962 W and C received the Nobel Prize in Medicine
    and Franklin died in 1958 never to receive the
    award currently recognized at Cambridge

23
http//www.accessexcellence.org/RC/AB/BC/Rosalind_
Franklin.php http//www.blinkx.com/video/rosalind-
franklin-dna-discoveries-in-science-and-art/A3fUh_
J7RZ77E7Njdd7zcA
24
DNA Nucleotides
  • DNA is a nucleic acid made of two long chains of
    Polymers made of monomers which is made of
    nucleotides
  • Nucleotide is made of 3 parts
  • 1. 5-carbon sugar (deoxyribose)
  • 2. Phosphate group
  • 3. Nitrogenous base

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27
Bonds hold DNA together
  • DNA looks like a spiral staircase
  • Covalent bonds and hydrogen bonds
  • Nitrogenous bases
  • 4 types
  • a. Purines- contain double ring of carbon
  • 1. Adenine
  • 2. Guanine
  • b. Pyrimidines- have a single ring of carbon
  • 3. Thymine
  • 4. Cytosine

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Complementary Bases
  • 1949- Chargaff observed percentages of A T, C G
  • Base-paring rules- single strand pairs up with
    second strand to make a double strand
  • Complementary base pairs- A T, C G
  • Base sequence- order of nitrogenous bases on a
    chain

30
DNA model
  • Looks like a ladder
  • Sugar-phosphate is the handrails
  • Base pairs are steps
  • Draw in the complementary base pairs to
  • AACCTGACTGGACAC

31
DNA replication Key Questions
  • Summarize the process of DNA replication
  • Identify the role of enzyme in the replication of
    DNA
  • Describe how complementary base paring guides DNA
    replication
  • Compare the number of replication forks in
    prokaryotic and eukaryotic cells during DNA
    replication
  • Describe how errors are corrected during DNA
    replication

32
Q and A
  • Q Why do you think gives DNA its stability even
    though the hydrogen bonds between the nitrogenous
    bases are easily broken?.
  • A Strong covalent bonds connect the sugar and
    phosphate groups of the DNA backbone

33
DNA Replication
  • Watson and Cricks discovery of the double helix
    structure of DNA caused great excitement in the
    scientific community. Scientists realized that
    this model could explain simply and elegantly how
    DNA can replicate exactly each time a cell
    divides, this is a key feature of hereditary
    material.

34
How DNA Replication occurs
  • Process by which DNA is copied in a cell before a
    cell divides by mitosis, meiosis, or binary
    fission
  • The two nucleotide strands of the original double
    helix separate along the strands
  • Strands become templates to make new
    complementary strands
  • Two identical DNA (double helix) separate and
    move to new cell during division

35
Steps of replication
  • Helicases- enzyme that separate the DNA strands,
    move along the molecule breaking the H-Bond
    between the complementary nitrogenous bases, a
    Y-shaped region is formed called the replication
    fork
  • DNA polymerase adds complementary nucleotides
  • DNA poly completes strand and falls off
  • DNA ligase links the pieces together
  • Get two identical DNA molecules
  • This is called a semi-conservative replication-
    keeps one of the original (conserved)

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41
Prokaryotic DNA Replication
  • In most prokaryotes, DNA replication does not
    start until regulatory proteins bind to a single
    starting point on the chromosome. This triggers
    the beginning of DNA replication.
  • Replication in most prokaryotic cells starts
    from a single point and proceeds in two
    directions until the entire chromosome is copied.

42
Eukaryotic DNA Replication
  • Eukaryotic chromosomes are generally much bigger
    than those of prokaryotes.
  • In eukaryotic cells, replication may begin at
    dozens or even hundreds of places on the DNA
    molecule, proceeding in both directions until
    each chromosome is completely copied.

43
Chapter 13 Key Terms
  • RNA
  • mRNA
  • rRNA
  • tRNA
  • Transcription
  • Translation
  • RNA Polymerase
  • Genetic code
  • Translation
  • Anticodon
  • Condon
  • Polypeptide
  • Gene expression
  • Mutations
  • Point mutation
  • Fram shift
  • mutatgens

44
Protein Synthesis
  • Characteristics such as hair color are largely
    determined by genetic factors. But how does
    inheriting a particular form of a gene result in
    the appearance of a specific hair color? The
    structure of DNA helps explain how genes function
    in making proteins that determine traits in an
    organism.

45
Misconception
  • Different cells, same DNA
  • You might think that because cells in the same
    organism appear different and have different
    functions, the cells must have different DNA.
  • The first fertilized egg undergoes DNA
    replication and then mitosis and then repeated to
    give every cell in the body the same DNA.
    (except for when crossing over takes place during
    meiosis to create gametes)
  • other factors determine which genes are used
    for the cells specific function

46
Key Questions
  • Outline the flow of genetic information in cells
    from DNA to protein
  • Compare the structure of RNA To DNA
  • Summarize the process of transcription
  • Describe the importance of the genetic code
  • Compare the role of mRNA, rRNA, tRNA in
    translation
  • Id the importance of learning about the human
    genome

47
Flow of genetic info
  • Gene- segment of DNA that is located on a
    chromosome and codes for a specific trait
  • Process in Eukaryotic cells
  • DNA ? transcription? RNA? translation ? protein
  • Transcription- DNA acts as a template for the syn
    of RNA

48
Flow of genetic info cont
  • 2. translation- RNA directs the assembly of
    proteins
  • 3. Protein synthesis- proteins are formed based
    on information in DNA and carried out by RNA
    (gene expression)
  • DNA (double stranded)? RNA (single)? Protein
  • Proteins are responsible for protecting the
    body against infections and carrying oxygen in
    red blood cells

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RNA Structure and Function
  • RNA is a nucleic acid made up of nucleotides
  • 4 major differences from DNA
  • 1. contain the sugar ribose not deoxyribose
  • 2. contains the nitrogenous base uracil not
    thymine
  • 3. single stranded not double
  • 4. usually much shorter in length

51
3 types of RNA
  1. mRNA- messenger- single stranded molecules that
    carries the instructions from a gene to make a
    protein (carries a message)
  2. rRNA- ribosomal- part of the structure of
    ribosome, ribosomes are made of rRNA and many
    proteins
  3. tRNA- transfer- transfers amino acids to the
    ribosome to make protein

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Transcription
  • Process in which genetic instructions in a gene
    are transcribed or rewritten into an RNA molecule
  • Steps
  • RNA polymerase binds to promoter. The promoter
    initiates transcription
  • Adds free RNA nucleotides that are complementary
    to the nucleotides on one of the DNA strands, DNA
    strands rewind
  • RNA poly reaches the terminal signal, makes the
    end of that gene, or a stop signal or stop codon

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The genetic code
  • Is the term that rules how a sequence of
    nitrogenous bases in nucleotides corresponds to a
    particular amino acid
  • The genetic code, three adjacent nucleotides in
    mRNA specify an amino acid in a polypeptide
  • Each 3-nucleotide sequence in mRNA encodes for a
    amino acid or signifies a start or stop signal
    called a codon 10.1tab
  • (Start is AUG) (stop are UAA, UAG, UGA)

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Translation- making of protein
  • Protein structure- one or more polypeptides,
    chains of AA linked by peptides bonds
  • Over 20 AA found in proteins of living things
  • AA are arranged to specific sequence
  • Shape always equals function

59
5 Steps of translation
  1. Initiation- tRNA and mRNA bind, on the tRNA is
    the anticodon (3 nucleotides on RNA that
    complements codon in mRNA)
  2. Elongation-the next AA binds to the codon,
    peptide bonds form between adjacent amino acids
  3. Elongation cont- first tRNA leaves and leaves it
    AA, elongating the chain
  4. Termination- stop codon is reached
  5. Disassembly- new polypeptide is released

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Human Genome
  • 3.2 billion base pair in the 23 human chromosomes
  • Take one person almost 10yrs to read the total
    sequence aloud
  • Bioinformatics- uses pc to compare different DNA
    sequences, aids in interpretation
  • Ability to treat diseases in the future

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Review Answers
  • Transcription
  • Nucleus
  • Steps
  • RNA Polymerase binds DNA unwinds
  • mRNA starts to form
  • DNA and mRNA are released

68
Review Cont
  • Translation
  • Cytoplasm
  • Steps
  • initiation tRNA binds to mRNA
  • Elongation first peptide bond forms
  • Elongation polypeptide chain grows
  • Termination protein is complete

69
DNA errors in replication
  • Errors are rare- like typing this book 1000xs
    with out mistakes
  • DNA polymerase have repair enzymes that proofread
    the strands and repair it
  • Mutation are changes in the nucleotide sequence
    of DNA molecule
  • Environmental factors can also disrupt or damage
    DNA
  • Studying DNA replication is one good way to
    understand and treat some cancers

70
Mutations
  • Change in the nucleotide-base sequence of a gene
    or DNA molecule
  • Germ-cell occurs in an organisms gametes, can
    be passed on to an offspring
  • Somatic-cell body cell and can affect the
    organism, skin cancer, leukemia, can not be
    inherited!!
  • Lethal mutations- cause death before birth
  • Can mutations be beneficial to the individual?

71
Chromosome Mutations
  • Two ways
  • 1. change in structure of chromosome
  • 2. adding or loosing a chromosome
  • Deletion- loss of a piecd of a chromosome due to
    breakage
  • Inversion- segments breaks off, flips around and
    reattaches
  • Translocation- breaks off and reattaches to non
    homologous chromosome
  • Nondisjunction- chromosome fails to separate from
    its homologous during meiosis, get and extra copy
    (trisomy 21)

72
Gene Mutations
  • Point mutations- substitution, addition, or
    removal of single nucleotide
  • Substitution- one nucleotide replaces another
  • Frameshift mutation- it just shifts down- creates
    new amino acids
  • Insertion mutations- addition of a gene and
    framshift occurs
  • ATCGA

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Answers to Review
  • Replication
  • ATGCAGTACGGTGGGCTG
  • TRANSCRIPTION
  • AUG-CAG-UAC-GGU-GGG-CUG
  • TRANSLATION
  • MET START- GLU-TYR-GLY-GLY-LEU..

77
MUTATIONS
  • TACGTCATGCCACCCGAC
  • 1. Change C to G
  • substitution- no start codon
  • TAG? AUC
  • 2. Remove T- deletion
  • AUG- CAG-UCG-GUG-GGC-UG
  • START-LEU-SER-VAL-ALA- X
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