DNA and PROTEIN SYNTHESIS by 5bS7l4

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									DNA and PROTEIN SYNTHESIS

       “Cracking the Code”
                     DNA
• the blueprint of life

• contains the instructions for making
  proteins within the cell.

• Deoxyribonucleic Acid

• Found in the nucleus of the cell
  (mitochondria also have DNA)
         The Shape of DNA
• very long polymer

• a ‘twisted ladder’ or zipper

• called a double helix.
        Structure of DNA
• A 5 carbon SUGAR
  (deoxyribose)& phosphate
  backbone

• rungs that connect the
  backbones are nitrogenous
  bases

• Nucleotide = sugar + phosphate
  + nitrogenous base
           Structure of DNA




Anti parallel: one strand runs 5’ to
3’, the other runs opposite
               4 DNA Bases
•    Purine base - double
     rings.
    – Adenine
    – Guanine

•    Pyrimidine base -
     single ring
    – Thymine
    – Cytosine
     Complementary Pairing
• complementary base pairs: normal
  pairing of nitrogenous bases is: 1 purine
  and 1 pyrimidine

• Adenine always and only binds with
  Thymine
    A-T
• Guanine always and only pairs with
  Cytosine
    G-C
            DNA Replication
• semi-conservative replication-new DNA
  molecule made of one parent and one newly
  replicated strand.
• In general a DNA molecule ‘unzips’ down the
  middle of the paired bases, 2 individual strands
  are made that will become the ‘templates’ for
  new complete DNA stands
   The Steps for DNA Replication (during S-
            phase of Interphase):
1. Initiation starts at a specific necletide
   sequence, a group of enzymes called DNA
   helicases breaks hydrogen bonds between
   bases to unzip the double helix

2. Proteins bind to keep strands apart
3) RNA primers attach to a spot on the
   original DNA stand

4) DNA polymerase III – starts at where the
   primer attached to the DNA and makes
   new strand in 5’ to 3’ direction (always)
5) DNA polymerase 1 – removes primers
   and replaces with nucleotide

6) DNA ligase – joins DNA fragments
DNA makes DNA
              DNA Editing
• AMAZING!!! DNA has a spell check

• DNA polymerase cut out mismatched
  base, and replace it with the proper
  nucleotides.
              Protein Synthesis
• Proteins -chains of amino acids.

• as small as 8 amino acids, and as large as over
  50,000 amino acids.

• There are 20 amino acids

• One Gene One Protein Theory - production of
  each protein is controlled by one gene.
         (Protein Function)
Functions:
 - Pigments – eg.
 Melanin – protect
 or signal etc.
         (Protein Function)
- enzymes – eg.
  Amylase – catalyze
  reactions
         (Protein Function)
- movement – eg.
  Actin in muscle
          (Protein Function)
• carriers – eg.
  Hemoglobin
  (oxygen)
        (Protein Function)
channels – in
  membranes (eg.
  Porin)
            (Protein Function)
•       - receptors –
    cell recognition eg.
    CD4 receptor on
    WBC (AIDS)
Essential amino acids
      Ribonucleic acid (RNA)
-required for protein synthesis,
1. RNA is single stranded, DNA is double stranded

2. The 5 carbon sugar is ribose in RNA,
  deoxyribose in DNA

3. RNA uses the base uracil instead of thymine.
  Uracil binds with adenine. (A-U )
                 3 Types of RNA

1. Messenger RNA (mRNA)
  •   takes DNA code to the ribosomes where proteins
      are made

2. Transfer RNA (tRNA)
  •   brings the appropriate amino acids from the
      cytoplasm to the ribosomes and strings them in
      order according to mRNA.
3. Ribosomal RNA (rRNA)

• not directly involved with protein synthesis

• makes the ribosomes in the nucleus
Protein Synthesis
     Steps in Protein Synthesis
1. Transcription
  • At a start sequence of neucleotides, the
    double stranded DNA opens up
    (unzipped by helicases again)
  • RNA polymerase attaches to the
    promoter and builds the single stranded
    mRNA
  • Stops at the termination sequence of
    nucleotides and mRNA detaches
  • mRNA makes its way to the ribosome for
    translation
2. Translation-making the protein
• mRNA attaches between the two
  subunits of a ribosome which “reads”
  the mRNA
 –   mRNA is a codon (represents a 3 nucleotide
     sequence from the DNA that it just read)


• tRNA brings amino acids from the
  cytoplasm to the ribosome
  – tRNA has an anticodon for an amino acid

  ex) If mRNA codes UUU, t RNA anticodon is
     AAA and it will get the amino acid PHE
              mRNA Codons

• 3 nitrogen bases that code for a specific
  amino acid –WHY 3?
• Start codon – starts protein synthesis,
  AUG which codes for methionine

• Stop codons – ends protein synthesis,
  UAA, UAG, UGA

• Intron – non-coding sequences

• Exon – coding sequences that make
  proteins
• Once translation is complete tRNA returns
  to the cytoplasm and mRNA is broken
  down.
 Why Do Firefly’s Glow?



• What Makes a Firefly Glow?
           DNA and Mutations
• inheritable changes

• Spontaneous or caused by
  mutagenic agents
  – Ex) radiation, chemicals

• may be as simple as a single base
  pair
             Basic Mutations:
1. Substitution of nucleotide(s), usually mild
   mutation created (but can be serious like sickle
   cell anemia)

2. Frameshift – changes the reading frame. A whole
   new sequence is read, usually leads to severe
   mutations. Framrshifts are caused by:
   a) Deletion of a nucleotide(s)
   b) Addition of extra nucleotide(s)

1. Translocation of a gene-DNA fragment switches
   location, often between different chromosomes.
   This is a very serious mutations (usually fatal)
• Mutations in body cells often have little
  consequences compared to mutations of
  the germ cells (sperm or egg).

• A single mistake in the DNA of a sperm or
  egg cell would be repeated billions of
  times if that cell underwent fertilization to
  become a complete individual.
                    Transposons
• are “jumping genes”,
  DNA sequences that
  have the ability to
  move in / out of
  chromosomes,
  changing their
  location. May cause
  mutations or change
  amount of DNA
• http://www.dnalc.org/vshockw
  ave/ac_ds_trans.dcr
       Oncogenes and Cancer
Cancer -uncontrolled cell division from a changed
 genetic code (uncontrolled mitosis)

Evidence:

     1. Cancerous cells often display nitrogen
  base substitutions

     2. Many known mutagens, are also known to
  cause cancer
3. segments of chromosomes extracted
   from cancerous mice transformed normal
   mouse cells into cancerous cells.
  -genes called oncogenes cause cancer
       Oncogenes and Cancer
• oncogenes are present in normal cells, and do
  not always result in cancer

• oncogenes must be transposed to another site
  on the chromosome to be activated
              The Ames Test
• To test for potential mutagens

• bacteria Salmonella typhimurium - unable to
  make histidine

• after the bacteria is exposed to a potential
  mutagen, it is grown in a culture without
  histidine.

• If it survives it has been mutated!
Biotechnology
• Biotechnology –biological systems used to
  produce a product.

• Genetic engineering –produces transgenic
  cells: foreign DNA inserted

• Recombinant DNA – DNA that comes
  from 2 or more sources.
• Vector –an organism (bacteria or virus) that
  carries and leaves its genetic material in a host
  cell. The host then replicates the vector’s genetic
  material.

• Plasmid – is circular DNA found in bacteria. This
  is often used as a vector in DNA recombination.
The process of creating recombinant
DNA involves 2 types of enzymes:
1. Restriction Enzymes – (DNA scissors) cut
   the DNA strand at specific sites -palindromes-
   and often creates sticky ends
2. The now unpaired segments can be
    paired with complimentary nucleotides
    from a different strand of DNA

3. DNA ligase – is genetic glue that puts
    DNA strands back together.

•   rDNA
                  Application
• Insulin used to be harvested from pigs, but some
  individuals did not tolerate it.

• we are now able to use bacteria to produce
  human insulin in large quantities.

• is tolerated much better by patients.

• This procedure was first marketed in Canada in
  1983!
Other Aspects of Biotechnology
• Gene sequencing –determining the
  specific location and composition of
  specific genes.

• The Human Genome Project -1990
  2000: mapped our 30 000 genes (3
  billion nucleotides)

• NOVA Online | Cracking the Code of Life |
  Sequence for Yourself
• RFLP – restriction fragment length
  polymorphism –cut DNA into pieces

• Gel Electrophoresis – separate the DNA
  pieces by size.
• DNA fingerprinting
  – identify an individual based on their
    unique genetic code.
  – homologous segments of DNA are
    similar but contain unique patterns of
    nitrogen bases
  – identify individuals involved in crimes,
    paternity
DNA Fingerprinting
         Misc. Technology
• Polymerase chain reaction –making
  billions of copies of a piece of DNA- PCR
  Animation

• Paternity Testing - Paternity Testing

• Gene Gun - Genegun1

								
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