Ch12 by xiangpeng

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									Chapter 12
 DNA & RNA
III. RNA & Protein Synthesis

  The double helix structure explains how DNA is
   copied,but not how a gene works-
   _______________are coded DNA instructions that
   control the production of protein in the cell.
  A. The structure of RNA
   Long chain of nucleotides
   3 main differences between DNA & RNA:
     Sugar is ____________
     Generally single-stranded
     RNA contains __________(U) in place of
       thymine (T)

                                        uracil
    genes            ribose
Interest Grabber
   Section 12-1


Order! Order!

Genes are made of DNA, a large, complex molecule. DNA is composed
of individual units called nucleotides. Three of these units form a code. The
order, or sequence, of a code and the type of code determine the meaning
of the message.
 1. On a sheet of paper, write the word cats. List the letters or units that
      make up the word cats.
 2. Try rearranging the units to form other words. Remember that each
    new word can have only three units. Write each word on your paper,
    and then add a definition for each word.
 3. Did any of the codes you formed have the same meaning?
 4. How do you think changing the order of the nucleotides in the
    DNA codon changes the codon’s message?
I.DNA
 A. Griffith & Transformation
 Frederick Griffith was trying to figure out how bacteria
  made people sick-how they cause a certain type of
  pneumonia.
 He isolated 2 strains(types) from mice-both cultured
  well,but only one caused pneumonia.The culture of the
  disease causing bacteria were
  __________________colonies while the other was
  rough.


           smooth
    1-Griffith’s experiments (1928)
     Mice injected w/ disease –causing strain got sick
       and died and nothing happened if injected w/other
       strain…He wondered if the disease-causing type
       made a toxin…?
     So he took some of disease strain and heated to kill
       bacteria and then injected into mice….mice survived
       suggesting it was not a toxin producing disease
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)
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)
     2-Transformation
     He mixed his heat –killed w/ live harmless bacteria and
      injected into mice…..________________________
     Somehow the disease –causing strain passed their
      disease capacity to harmless bacteria….. disease –
      causing strain found in lungs
     He called this changing of one bacteria by the genes of
      another _____________________....Thus a
      factor(gene) from heat killed disease –causing strain
      was passed on.




    Mice developed
    pneumonia                        transformation
B. Avery & DNA


 Team of scientists lead by Avery in 1944 repeated
  Griffith’s experiment in order to determine which
  molecule was responsible for the transformation.
 They made an extract from the heat-killed bacteria
  and treated it w/enzymes that kill proteins,lipids and
  other molecules,inc. RNA
Avery cont’d         transformation


 ____________________still occurred so the above
  molecules were not responsible for transformation
 They repeated the experiment but used enzymes that
  kill____________, stopping transformation…. DNA
 Therefore ________caused the transformation and
  thus stores and transmits genetic info
C. The Hershey –Chase Experiment


 1952-Alfred Hershey and Martha Chase studied
  viruses-disease-causing particles smaller than a cell.
 ______________________-virus that infects
  bacteria.They have a DNA or RNA core and a protein
  coat…They attach to the surface of a bacterium and
  inject genetic info into cell.The viral genes act to
  produce many new bacteriophages and eventually
  destroy bacterial cell,w/_____________bursting out.


                               viruses
bacteriophage
 They grew viruses in cultures containing
  _________________________________,mixed them
  w/bacteria and waited a few min. for viruses to inject
  genetic material.
 Then they separated the bacteria from the viruses
  and tested bacteria for radioactive marker…..nearly
  all the radioactivity was P-32-found in _________----
  thus concluding it was the genetic material was
  DNA !




  Radioactive                       DNA
  markers
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
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
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
D. The Components and Structure of
DNA

 Scientists questioned how the DNA molecule could
  do three things 1)carry info from 1 generation to the
  next 2)putting that info to work and 3)could be easily
  copied
 DNA is a long molecule made of units called
  ___________________________________________-




        nucleotides
The nucleotide is made of 3 basic
 parts:______________________(sugar),
 a phosphate group and
 a_________________________________

deoxyribose         Nitrogenous base
 2 nitrogenous bases are purines(have 2
  rings):___________________________(A)and_______
  (G)
 2 other nitrogenous bases are pyrimidines (have 1
  ring):____________________(C)and
  ____________________________(T)


                                          Cytosine and
                                          thymine
     Adenine ,guanine



--backbone made by sugar and phosphate w/ bases sticking
out sideways
Figure 12–5 DNA
 Section 12-1
Nucleotides
                    Purines              Pyrimidines
                Adenine    Guanine   Cytosine        Thymine




                   Phosphate
                   group                        Deoxyribose
   1-_______________________Rules-discovered that
    %’s of Cytosine and guanine were almost equal in
    DNA and the same was true for adenine and
    thymine….Thus A pairs w/T and C w/ G-BASE
    PAIRING




          Chargaff’s Rules
Percentage of Bases in Four
Organisms
 Section 12-1




  Source of DNA    A      T      G      C

  Streptococcus   29.8   31.6   20.5   18.0

  Yeast           31.3   32.9   18.7   17.1

  Herring         27.8   27.5   22.2   22.6

  Human           30.9   29.4   19.9   19.8
    2- X-ray evidence-1950’s –Rosalind Franklin
     used X-ray diffraction to learn about DNA
     structure----The scattered X pattern seen begins to
     show the __________-partial TWISTED
     STRUCTURE of DNA


    helix
     3---Double helix_
   Watson and Crick -2 strands wound around each
    other---like the twisted ladder or spiral staircase
   Strands held together by H-bonds
Figure 12–7 Structure of
 Section 12-1
DNA
                    Nucleotide

                                     Hydrogen
                                     bonds




  Sugar-phosphate
         backbone
                                 Key
                                 Adenine (A)
                                 Thymine (T)
                                 Cytosine (C)
                                 Guanine (G)
Interest Grabber
  Section 12-2




 A Perfect Copy

 When a cell divides, each daughter cell receives
  a complete set of chromosomes. This means
  that each new cell has a complete set of the
  DNA code. Before a cell can divide, the DNA
  must be copied so that there are two sets ready
  to be distributed to the new cells.
Section 12-2
1.   On a sheet of paper, draw a curving or zig-
     zagging line that divides the paper into two
     halves. Vary the bends in the line as you draw it.
     Without tracing, copy the line on a second sheet
     of paper.
2. Hold the papers side by side, and compare the
   lines. Do they look the same?
3. Now, stack the papers, one on top of the other,
   and hold the papers up to the light. Are the lines
   the same?
4. How could you use the original paper to draw
   exact copies of the line without tracing it?
5. Why is it important that the copies of DNA that
   are given to new daughter cells be exact copies
   of the original?
II. Chromosomes & DNA Replication


A-DNA & Chromosomes
 In cytoplasm in prokaryotes
 In _______________________found in cell
  nucleus in the form of a number of
  chromosomes(46 humans,8 Drosophilia and
  22 Sequoia trees)


   eukaryotes
 1--DNA length
   1.6 mm in E.coli(has 4,639,221 base pairs)---
    obviously it must be tightly folded
    2-Chromosome Structure
     Eukaryotic cells have about 1000 times as many
       base pairs of DNA than a bacterium
     Humans cells have ~ 1 m DNA
     Eukaryotic chromosomes contain DNA and a
       protein ,which together make
       _____________________-consisting of DNA
       tightly packed around proteins called histones


      chromatin
   DNA and histone together make
     beadlike_____________________________
   Nucleosomes pack together to make thick
     fibers,drawn together during mitosis…also
     separating
 Role of nucleosomes-fold great lengths of DNA into
  tiny spaces



         nucleosomes
Prokaryotic Chromosome Structure
 Section 12-2




     Chromosome



  E. coli bacterium
                       Bases on the chromosome
                   Figure 12-10 Chromosome Structure
                   of Eukaryotes
Section 12-2




   Chromosome               Nucleosome

                                                       DNA
                                                       double
                                                       helix
                                    Coils

               Supercoils




                                         Histones
B. DNA Replication


   Each strand of DNA double helix has all the info
    to___________________________by base pairing
   Strands are complementary
   In prokaryotes,this begins @single point and
    proceeds-often in 2 directions
   In Eukaryotes,DNA replication begins @ 100’s of
    places,going both directions until complete
   __________________________is where replication
    occurs

Reconstruct the              Replication fork
other half
    1-Duplicating DNA
     __________________________or duplication of
       DNA happens before cell division---ensuring
       each cell has a complete set of DNA molecules
     Each strand of a double helix serves as a
       _____________________or model for new strand
     A pairs w/ T and C w/ G


                            template
    replication
    2-How Replication Occurs
     Carried out by a series of enzymes that unzip a
       molecule
     ____________________________________ joins
       individual nucleotides to make a DNA
       molecule….also proof reads the new strands




     DNA
     polymerase
Figure 12–11 DNA
 Section 12-2
Replication
                                         Original
                                         strand         DNA
                         New strand                     polymerase




                                       Growth
                 DNA
                 polymerase
                                      Growth




   Replication                                               Replication   Nitrogenous
   fork                                                      fork          bases



                                          New strand   Original
                                                       strand
       III. RNA & Protein Synthesis


  The double helix structure explains how DNA is
   copied,but not how a gene works-
   _______________are coded DNA instructions that
   control the production of protein in the cell.
  A) The structure of RNA
   Long chain of nucleotides
   3 main differences between DNA & RNA:
     1--Sugar is _________________
     2---Generally single-stranded
     3---RNA contains ________________(U) in
        place of thymine (T)

                                uracil   ribose
    genes
                                     Protein
B. Types of RNA                      synthesis

   Main job=_________________-ie the assembly of amino
    acids into proteins
   3 Types:
     ____________________(mRNA)-carry copies for
       instructions from DNA to rest of cell
     ____________________(rRNA)-type of RNA that helps
       make up ribosomes,where proteins assembled
     ________________(tRNA)transfers each amino acid to
       the ribosome as it is coded for on mRNA.

      messenger


                  ribosomal               Transfer
 Concept Map
       Section 12-3

                                                              RNA



                                                             can be



        Messenger RNA                                   Ribosomal RNA                           Transfer RNA




also called     which functions                also called      which functions to    also called   which functions
                       to
                                                                                                           to
                                                                                                             Bring
                                                                       Combine
 mRNA                Carry instructions          rRNA                                    tRNA           amino acids to
                                                                      with proteins
                                                                                                          ribosome



              from                        to                          to make up



              DNA                   Ribosome                          Ribosomes
C. Transcription-produces RNA molecules by copying
part of nucleotide sequence of DNA into a
complementary sequence in RNA

   Requires enzyme known as
    _______________________________________-
    binds to DNA and separates DNA strands.Then
    uses one strand as template to make RNA
   The enzyme only binds to areas known as
    promoters-signals that indicate where to make
    RNA.Similar signals tell where to stop

RNA-polymerase
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
D. RNA editing
  ________________________ in eukaryotic genes
   ,sequences of nucleotides that ARE NOT
   involved in coding for proteins
  _______________________-DNA sequence that
   does code for protein

                            exons

introns
E. Genetic Code            polypeptide




   ______________________-chain of amino
     acids=proteins                    codon
   _________________-3 consecutive nucleotides
     that specify a specific amino acid
 Example –UCGCACGGU reads UCG_CAC_GGU
   and codes for Serine-Histidine-Glycine
     The Genetic Code
Section 12-3
Universal code
64 possible 3 base codons
AUG can specify methionine or start
 codon
3 stop codons that do not code for an
 amino acid
F. Translation               ribosome

   ______________________reads the instructions
    for the order in which amino acids should be joined
    by reading mRNA
                         translation
   ____________________________is the decoding
    of an mRNA message into a polypeptide(protein)
   Before translation occurs,mRNA is transcribed from
    DNA and released into
    __________________________.    cytoplasm
   Translation begins when mRNA molecule in
    cytoplasm attaches to a _____________________.

                                     ribosome
    As each codon of the mRNA moves through the
     moves through the                      tRNA
     ribosome,_____________brings in the
     proper,indicated amino acid and transferred to
     polypeptide chain
    Each tRNA carries one kind of amino acid
    __________________ is a group of 3 bases on a
     tRNA that are complementary to a mRNA codon
    Ribosome forms a _________________bond
     between amino acids and breaks tRNA bond
     releasing it
    Protein keeps growing until ribosome reaches
     stop codon on mRNA
                               peptide
anticodon
Figure 12–18 Translation
 Section 12-3
Figure 12–18 Translation (continued)
 Section 12-3
           Changes in genetic material
Mutations=________________________
                                          Gene mutation
          A.---Kinds of Mutations
             1)
             ________________________________-changes in a
              single gene
       _____________________________________-changes in 1 or
        a few nucleotides-@ a single point in DNA-includes
        substitutions,insertions and deletions
       Substitutions usually affect no more than 1 amino acid
       ____________________________________-insertions or
        deletions where the reading frame of the codon message is
        changed-can VERY much alter or even stop the function of
        a protein


Point               Frameshift
mutation            mutation
        2)Chromosomal Mutations-change in the # or
          structure of chromosomes-can change the
          location of genes on chromosomes and /or
          number of copies of some genes.
   4 types-1)Deletions-loss of all or part of a
    chromosome
   2)__________________-extra copies of a part of a
    chromosome
   3)________________reverse directions of parts of
    chromosomes
   4)____________-part of one chromosome breaks
    off and attaches to another
                                 translocations
duplication
                  inversions
                       Gene Mutations: Substitution, Insertion,
                       and Deletion
Section 12-4




               Substitution                                Deletion
                                        Insertion
Figure 12–20 Chromosomal
 Section 12-4
Mutations
                      Deletion




                      Duplication




                      Inversion




                      Translocation
B. Significance of Mutations


 Many have no effect
 Harmful effects include genetic disorders and cancer
 ________________________-contains extra set of
  chromosomes-bad in most cases but often helpful in
  PLANTS.



  polyploidy
    V. Gene Regulation           operon

      Only a fraction of a gene expressed at one time
      ___________________-group of genes that
       operate together
      ________________-where repressor binds operon
       (when it)is turned off
      Operons not usually found in eukaryotes-these
       genes are usually controlled individually and
       regulation more complex---mainly because of cell
       specialization
      Hox genes-control differentiation of cells and
       tissues in the embryo


        operator
Typical Gene Structure
 Section 12-5




                   Promoter
      Regulatory
                   (RNA polymerase
        sites                                  DNA strand
                   binding site)




                       Start transcription   Stop transcription
Karyotypes

								
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