Documents
Resources
Learning Center
Upload
Plans & pricing Sign in
Sign Out

Chapter 12_ DNA and RNA

VIEWS: 17 PAGES: 98

									Chapter 12:
  DNA and
   RNA
Learning Targets for Section 12-1


• Summarize the relationship between
  genes and DNA?
• Describe the overall structure of
  DNA?
     12–1 Research Behind DNA
     Griffith and Transformation

   In 1928, British scientist Frederick Griffith
    tried to determine which bacteria produced
    pneumonia.


• Griffith isolated two different strains.
  1. disease-causing = smooth colonies
  2. harmless strain = rough colonies.
       Griffith's Experiment


• Griffith injected mice

1. disease-causing bacteria- mice developed
  pneumonia and died.
2. harmless strain - didn’t get sick at all
 Experiment cont.

• Griffith’s then mixed heat-killed,
  disease-causing bacteria with live,
  harmless ones and injected the mixture
  into mice
• Mice developed pneumonia and many died.
• Found their lungs filled with the disease-
  causing bacteria
                Figure 12–2 Griffith’s
                     Experiment
           Section 12-1

                                                                                             Heat-killed,
                                                                                             disease-causing
                                                                                             bacteria (smooth
                                                                                             colonies)



           Disease-causing    Harmless bacteria Heat-killed, disease-     Control            Harmless bacteria
           bacteria (smooth    (rough colonies) causing bacteria        (no growth)          (rough colonies)
              colonies)                         (smooth colonies)




             Dies of pneumonia      Lives         Lives                                    Dies of pneumonia
                                                                Live, disease-causing
                                                              bacteria (smooth colonies)


Go to
Section:
           Figure 12–2 Griffith’s Experiment
           Section 12-1

                                                                                             Heat-killed,
                                                                                             disease-causing
                                                                                             bacteria (smooth
                                                                                             colonies)



           Disease-causing    Harmless bacteria Heat-killed, disease-     Control            Harmless bacteria
           bacteria (smooth    (rough colonies) causing bacteria        (no growth)          (rough colonies)
              colonies)                         (smooth colonies)




             Dies of pneumonia      Lives         Lives                                    Dies of pneumonia
                                                                Live, disease-causing
                                                              bacteria (smooth colonies)


Go to
Section:
           Figure 12–2 Griffith’s Experiment
           Section 12-1

                                                                                             Heat-killed,
                                                                                             disease-causing
                                                                                             bacteria (smooth
                                                                                             colonies)



           Disease-causing    Harmless bacteria Heat-killed, disease-     Control            Harmless bacteria
           bacteria (smooth    (rough colonies) causing bacteria        (no growth)          (rough colonies)
              colonies)                         (smooth colonies)




             Dies of pneumonia      Lives         Lives                                    Dies of pneumonia
                                                                Live, disease-causing
                                                              bacteria (smooth colonies)


Go to
Section:
  Griffith’s Conclusion:

• Griffith hypothesized some factor
  transformed harmless cells into the
  heat-killed harmful cells
             Griffith movie
       Avery and DNA
• Avery and his colleagues repeated
  Griffith’s experiment then:
• Used enzymes that destroyed proteins,
  lipids, carbohydrates, and other
  molecules, including the nucleic acid RNA
• When they destroyed the nucleic acid
  (DNA), transformation did not occur
    Avery’s Conclusion:
• Avery and other scientists
  discovered that DNA is the nucleic
  acid that stores and transmits the
  genetic information from one
  generation of an organism to the
  next
The Hershey Chase Experiment

• Martha Chase and Alfred Hershey
  The Hershey Chase Experiment

• Studied viruses, nonliving particles smaller than a
  cell that can infect living organisms
• Hershey and Chase reasoned that if they could
  determine which part of the virus—the protein coat
  or the DNA core—entered the infected cell, they
  would learn whether genes were made of protein or
  DNA
• They grew viruses in cultures of radioactive isotopes
  of phosphorus-32 (32P) and sulfur-35 (35S).
The Hershey Chase Experiment

 • Proteins contain almost no phosphorus
   and DNA contains no sulfur
 • If 35S was found in the bacteria, it
   would mean that the viruses’ protein had
   been injected, If 32P was found in the
   bacteria, then it was the DNA that had
   been injected
    Figure 12–4 Hershey-Chase
            Experiment
           Section 12-1




                  Bacteriophage with     Phage infects   Radioactivity inside
                  phosphorus-32 in       bacterium       bacterium
                  DNA




                  Bacteriophage with     Phage infects   No radioactivity inside
                  sulfur-35 in protein   bacterium       bacterium
                  coat



Go to
Section:
    Figure 12–4 Hershey-Chase
            Experiment
           Section 12-1




                  Bacteriophage with     Phage infects   Radioactivity inside
                  phosphorus-32 in       bacterium       bacterium
                  DNA




                  Bacteriophage with     Phage infects   No radioactivity inside
                  sulfur-35 in protein   bacterium       bacterium
                  coat



Go to
Section:
    Figure 12–4 Hershey-Chase
            Experiment
           Section 12-1




                  Bacteriophage with     Phage infects   Radioactivity inside
                  phosphorus-32 in       bacterium       bacterium
                  DNA




                  Bacteriophage with     Phage infects   No radioactivity inside
                  sulfur-35 in protein   bacterium       bacterium
                  coat



Go to
Section:
Hershey and Chase’s Conclusion:


Hershey and Chase concluded that
the genetic material of the
bacteriophage was DNA, not protein.
           REVIEW
• In your science journal:
  • List as many scientists you can remember
  • And describe their contribution to our
    understanding of DNA
  • Pass your paper to your neighbor. Add to
    your neighbors list and/or correct what
    they have written.
DNA Introduction


   DNA Introduction
   The Structure of DNA
• DNA is a long molecule made up of units
  called nucleotides
• Each nucleotide is made up of three parts:
 1. a 5-carbon sugar called deoxyribose,
 2. a phosphate group,
 3. and a nitrogenous (nitrogen- containing)
    base
 There are four kinds of
nitrogenous bases in DNA
• Purines:
  • Adenine: Expressed A
  • Guanine: Expressed G
• Pyrimidines:
  • Thymine: Expressed T
  • Cytocine: Expressed C
                 Figure 12–5 DNA Nucleotides
           Section 12-1




                               Purines                   Pyrimidines
                          Adenine       Guanine   Cytosine      Thymine




                                    Phosphate
                                    group                Deoxyribose

Go to
Section:
DNA Structure


   DNA Structure
        Chargaff’s Rules

• Erwin Chargaff, an American biochemist,
  discovered that the percentages of guanine
  [G] and cytosine [C] are almost equal in any
  sample of DNA
• The same thing is true for adenine [A] and
  thymine [T]
• Despite the fact that DNA samples from
  organisms obeyed this rule, neither Chargaff
  nor anyone else had the faintest idea why
      X-Ray Evidence

• In the early 1950s, a British scientist
  named Rosalind Franklin began to study
  DNA using a technique called X-ray
  diffraction
• The X-shaped pattern in the image shows
  that the strands in DNA are twisted
  around each other like the coils of a
  spring, a shape known as a helix
            The Double Helix


• At the same time Francis Crick, and
  James Watson, were trying to understand
  the structure of DNA by building three-
  dimensional models of the molecule
• In 1953, Watson was shown a copy of
  Franklin’s X-ray pattern. In his book The
  Double Helix, Watson wrote: “The instant
  I saw the picture my mouth fell open and
  my pulse began to race.”
Watson and Crick’s Conclusion:

- DNA is a double helix in which two
  strands are wound around each other.
-   Each strand is made up of a chain of
    nucleotides.
-   The two strands are held together by
    hydrogen bonds between adenine and
    thymine and between guanine and cytosine.
Structure of DNA
DNA Structure


   DNA Structure
DNA Structure Activity


    DNA – The Double Helix
Learning Targets for Section 12.2

• Summarize the events that happen in
  DNA replication
• Relate the DNA molecule to
  chromosome structure.
  12–2 Chromosomes and
     DNA Replication
DNA and Chromosomes
 Most prokaryotes have a single circular
 DNA molecule that contains nearly all of
 the cell’s genetic information
           Prokaryotic Chromosome
                  Structure
           Section 12-2




               Chromosome

           E. coli bacterium


                               Bases on the chromosome




Go to
Section:
    Differences between
 Prokaryotes and Eukaryotes
• Eukaryotic DNA is a bit more complicated.
  Many eukaryotes have as much as 1000 times
  the amount of DNA as prokaryotes
• DNA Length DNA molecules are surprisingly
  long
• The chromosome of the prokaryote E. coli,
  contains 4,639,221 base pairs
      Length of DNA
• This means that the nucleus of a
  human cell contains more than 1
  meter of DNA
• How can so much DNA be packed
  into each and every cell in our
  body?
        Chromosome Structure
• Eukaryotic chromosomes contain both
  DNA and protein, tightly packed
  together to form a substance called
  chromatin
• Chromatin consists of DNA that is
  tightly coiled around proteins called
  histones
     Chromosome Structure


• Together, the DNA and histone molecules
  form a beadlike structure called a
  nucleosome
• This allows the chromosomes to be very
  tightly coiled up in the nucleus
                          Figure 12-10 Chromosome
                            Structure of Eukaryotes
           Section 12-2




           Chromosome              Nucleosome

                                                                   DNA
                                                                   double
                                                                   helix

                                                Coils

                      Supercoils




                                                        Histones


Go to
Section:
DNA Structure Activity


        Doublin’ DNA
           DNA Replication

• When Watson and Crick discovered the
  double helix structure of DNA, there was
  one more remarkable aspect that they
  recognized immediately.
  • The structure explained how DNA could be
    copied, or replicated
  • Each strand of the DNA double helix has all the
    information needed to reconstruct the other half by
    the mechanism of base pairing
DNA Replication


 DNA Replication video
         DNA Replication
• During DNA replication, the DNA molecule
  separates into two strands
• Then produces two new complementary
  strands following the rules of base pairing.
• Each strand of the double helix of DNA
  serves as a template, or model, for the new
  strand
           Section 12-2


             Figure 12–11 DNA Replication
                                                   Original
                                   New strand      strand        DNA
                                                                 polymerase




                                                 Growth
                           DNA
                           polymerase
                                                Growth




             Replication                                              Replication   Nitrogenous
             fork                                                     fork          bases



                                                  New strand   Original
                                                               strand


Go to
Section:
DNA Replication

   DNA replication animation
   How DNA Replicates

• Start with a double strand of DNA
• DNA replication is carried out by a series
  of enzymes. which “unzip” a molecule of
  DNA
How DNA Replicates

 A–T     I’ve deleted
         the sugar-
         phosphate
 G–C     backbone for
         easier
 A–T     drawings

 C–G
 T–A     Hydrogen bonds


 C–G
  DNA Unzips

A–T                      A-T
G–C                       G-C
A–T                     A     T
C–G   DNA           C             G
T–A   unzips    T                     A
C–G            C                       G
                             A–T
                             G–C
                             A     T
DNAP III moves
along each strand
                         C             G
adding a base pair
                     T                 A
at a time
                     C                     G
                    A–T
                    G–C
                    AT    T
DNAP III
continues to
                   CG         G
moves along
               T              TA
each strand
adding a       C               CG
base pair at
a time
     A–T
     G–C
     AT   AT
 CG        CG
TA             TA
CG             CG
Finally get 2 new strands,
        exact copies
AT        AT
GC        GC
AT        AT
CG        CG
TA        TA
CG        CG
      STOP: Practice
Replicate the following strand of DNA
• ATG GGA CCG TAT ACG GAG
• TAC CCT GGC ATA TGC CTC
       DNA and Enzymes
• DNA replication involves a host of enzymes and
  regulatory molecules
• The principal enzyme involved in DNA
  replication is called DNA polymerase
• In addition to replication DNA polymerase also
  “proofreads” each new DNA strand, helping to
  maximize the odds that each molecule is a
  perfect copy of the original DNA
DNA Replication Video


      DNA Replication 2
Learning Targets for Section 12.3
 • What are the three main types of
   RNA?
 • What is transcription?
 • What is translation?
     12–3 RNA and Protein
          Synthesis

• The double helix structure explains how
  DNA can be replicated but it does not
  explain how a gene works
• Genes are coded DNA instructions that
  control the production of proteins
Genes, Protein and DNA


    Genes, Protein and DNA
                   RNA
• The first step is to copy part of the nucleotide
  sequence from DNA into RNA a process called
  transcription
• RNA molecules then carry out the process of
  making proteins.
• RNA molecule is a working copy of a single gene.
• Using RNA makes it possible for a single gene to
  produce hundreds or even thousands of RNA
  molecules
    The Structure of RNA
There are three main differences between
  RNA and DNA:
1. The sugar in RNA is ribose instead of
    deoxyribose
2. RNA is generally single-stranded
3. RNA contains uracil in place of thymine
             Types of RNA
 There are three main types of RNA: messenger RNA,
   ribosomal RNA, and transfer RNA.
1. messenger RNA (mRNA) serves as “messengers” from
   DNA to the rest of the cell.
2. ribosomal RNA (rRNA) is the site where Proteins are
   assembled on ribosomes
3. transfer RNA (tRNA) transfers each amino acid to the
   ribosome during the construction of a protein.
         Transcription
• During transcription, RNA polymerase
  binds to DNA and separates the DNA
  strands.
• RNA polymerase then uses one strand of
  DNA as a template from which
  nucleotides are assembled into a strand
  of RNA
            Figure 12–14 Transcription
           Section 12-3



                 Adenine (DNA and RNA)
                 Cystosine (DNA and RNA)
                 Guanine(DNA and RNA)
                 Thymine (DNA only)
                 Uracil (RNA only)




                                                  RNA
                                            polymerase

                                                  DNA
                                           RNA




Go to
Section:
Transcription

 Transcription Movie
    Practice Transcribing
• Remember A goes with T, C goes with G
  and Uracil takes the place of Thymine
• TAC GCA CCA TAT CCG ATT
• AUG CGU GGU AUA GGC UAA
        Where to Begin?
• The enzyme will bind only to regions of
  DNA known as promoters, which have
  specific base sequences.
• Promoters are signals in DNA that indicate
  to the enzyme where to bind to make RNA
• Similar signals in DNA cause transcription
  to stop when the new RNA molecule is
  completed
          Editing RNA
Many RNA molecules have sections, called
introns, edited out of them before they
become functional.
The remaining pieces, called exons, are
spliced together.
Then, a cap and tail are added to form the
final RNA molecule.
       The Genetic Code
• The “language” of mRNA instructions is
  called the genetic code.
• RNA contains four different bases: A, U,
  C, and G.
• In effect, the code is written in a
  language that has only four “letters.”
       STOP THINK!
• What is the process of transcription
  making?
• Where does transcription take place?
• What enzymes are used to complete
  transcription?
• Compare and Contrast DNA and RNA?
          Genetic Code
 The genetic code is read three letters at
 a time
 Each three-letter “word” in mRNA is
 known as a codon
 A codon consists of three consecutive
 nucleotides that specify a single amino
 acid that is to be added to the
 polypeptide
         Genetic Code
• Because there are four different bases,
  there are 64 possible three-base codons
  (4 × 4 × 4 = 64).
• The codon, AUG, that can either specify
  methionine or serve as the initiation, or
  “start,” codon for protein synthesis
• There are three “stop” codons that do
  not code for any amino acid
          Translation
• During translation, the cell uses
  information from messenger RNA to
  produce proteins
• This process is known as translation
         Translation
• Before translation can occur,
  messenger RNA must first be
  transcribed from DNA in the nucleus
  and released into the cytoplasm
• Translation begins when an mRNA
  molecule in the cytoplasm attaches to
  a ribosome
                 Figure 12–18 Translation
           Section 12-3



                                                                          Nucleus
                          Messenger RNA
                          Messenger RNA is transcribed in the nucleus.




                                                                         Lysine          mRNA
                             Phenylalanine         tRNA
                                                                           Transfer RNA
                     Methionine
                                                                           The mRNA then enters the cytoplasm and
                                                                           attaches to a ribosome. Translation begins at
                                                                           AUG, the start codon. Each transfer RNA has
                                                                           an anticodon whose bases are complementary
                                                                           to a codon on the mRNA strand. The ribosome
                                                                           positions the start codon to attract its
                                                                           anticodon, which is part of the tRNA that binds
                                                                           methionine. The ribosome also binds the next
              Ribosome                                                     codon and its anticodon.




             mRNA                                 Start codon


Go to
Section:
           Translation
• As each codon of the mRNA molecule
  moves through the ribosome, the proper
  amino acid is brought into the ribosome and
  attached to the growing polypeptide chain
• That job is done by transfer RNA
 Translation

• The codon matches up with
  complementary bases on the tRNA to
  tell it which amino acid to bring in
• The three bases on the tRNA
  molecule, called the anticodon, are
  complementary to one of the mRNA
  codons
          Translation
• The polypeptide chain continues to
  grow until the ribosome reaches a
  stop codon on the mRNA molecule
• At that point the protein is released to
  be modified in the Golgi apparatus or to
  be shipped out to perform its function
                          Figure 12–18 Translation
                                (continued)
           Section 12-3




            The Polypeptide “Assembly Line”
                                                                                     Growing polypeptide chain
            The ribosome joins the two amino acids—
            methionine and phenylalanine—and breaks
            the bond between methionine and its tRNA.
            The tRNA floats away, allowing the ribosome
                                                                                                             Ribosome
            to bind to another tRNA. The ribosome moves
                                                             tRNA
            along the mRNA, binding new tRNA molecules
            and amino acids.

                            Lysine            tRNA




                                                                    mRNA
                                                                           Completing the Polypeptide
                                                                           The process continues until the ribosome reaches
                                                                           one of the three stop codons. The result is a
    mRNA                             Translation direction                 growing polypeptide chain.
                   Ribosome



Go to
Section:
      Practice Translating
• original DNA    ATG CCC AGT TCA TAA
Compl DNA =       ___ ___ ____ ___ ____
mRNA =            ____ ___ ____ ____ ____
• Amino acid ______________,
  _______________, _____________,
  ______________, _____________.
 Check these answers first
• original DNA   ATG CCC AGT TCA TAA

• Compl DNA =    TAC GGG TCA AGT ATT

• mRNA =         AUG CCC AGU UCA UAA
   Amino Acid Answers
Amino acid
• methionine,   proline,
• serine, serine,       stop
      Translation and Transcription



   mRNA, tRNA, and Protein Synthesis

The Genetic Code: Codons and Amino Acids
    BELLRINGER 11/11/09
• COMPARE/CONTRAST RNA TO DNA
                  *** Include as much
                  information about each
                  that you can think of


                   THEN DESCRIBE what
                   happens during
                   TRANSCRIPTION
                   And DESCRIBE WHAT
                   HAPPENS DURING
                   TRANSLATION
     12.4 Learning Targets
• Describe how gene mutations and
 chromosomal mutations occur

• Understand the difference between
 point mutations and frameshift
 mutations
 Ways variations can arise


•What is a mutation and where can it occur?
      Inheritable change in genetic code
     * 99.9 % are harmful. Only 0.1% are helpful!!

 •What is a chromosomal mutation?
       Changes in number or structure of chromosome

•When do chromosomal mutations occur?
     During Meiosis – A cell division that produces
gametes
   TYPES OF MUTATIONS
• What is a frameshift mutation?
 Change that shifts the genetic message
 through inserting or deleting a nucleotide


• What is a point mutation?
    Change at one point of a chromosome.
•What is a deletion mutation?
      Loss of one or more genes




•What is a duplication mutation?
      One or more genes are copied twice



•What is an inversion mutation?
      Part of a chromosome gets turned the wrong way

								
To top