DNA and RNA

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DNA and RNA

• Chapters 12 13

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Hershey and Chase

• Performed two experiments to show that DNA is
  genetic material.
• Worked with viruses to determine if it was the
  protein or the DNA that contained the genetic
  information.

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Experiment One

• Bacteria were grown with a radioisotope of
  sulfur. The sulfur was used as a tracer.
• Viruses (bacteriophages) were allowed to infect
  the bacterial cells.
• Viral proteins were made within the host cell and
  contained the sulfur tracer.

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• The viruses were then allowed to infect a group
  of bacteria without the tracers.
• The colonies were spun in a blender to remove the
  viral protein coat.
• There was no tracer in the fluid medium, but
  there was still tracer within the bacterial cells.

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Experiment Two

• This was a repeat of experiment one, but
  phosphorous was added as a trace.

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Watson and Crick

• Working with everything they knew about the
  chemical properties of DNA, they were able to
  construct a model of DNA out of wire and metal
  pieces.

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Parts of a nucleotide

• 5-Carbon Sugar called deoxyribose (in DNA) or
  ribose (in RNA)
• Phosphate Group
• Nitrogenous Base these are what make the
  nucleotides different.

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• Purines are 2 ringed Adenine or Guanine

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• Pyrimidines are 1 ringed Thymine or Cytosine

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• Adenine binds to Thymine
• Guanine binds to Cytosine
• A purine will always bind to a pyrimidine to
  produce a base pair

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• Two strands of nucleotides are held together by
  hydrogen bonds between bases. They coil to form a
  Double Helix.

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Replication of DNA occurs during the S-phase of
Interphase

1. Proteins and enzymes (helicase) break the
   hydrogen bond between the bases causing the helix
   to unwind and expose the bases
2. Free Nucleotides (those within the nucleus) pair
   with the exposed bases with the help of DNA
   polymerase.
3. DNA Ligase (enzyme) ensures that all parts of the
   DNA strand are connected.

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• 4. The DNA Strands will coil again creating two
  new identical strands.
• Result Each strand will have one side from the
  original DNA and one side that is new.

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RNA

• Single Strand not a double helix
• The four bases are different adenine, cytosine,
  guanine, uracil
• Adenine bonds to uracil
• Guanine bonds to cytosine
• RNA gets its code from the DNA code

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3 types of RNA

• Messenger (mRNA) carries protein building
  instructions. Goes from the DNA in the nucleus to
  the ribosome
• Ribosomal (rRNA) makes up the ribosome
• Transfer (tRNA) delivers amino acids to the
  ribosomes. Has an anticodon specific to the amino
  acid.

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Protein Synthesis

• Occurs in 2 processes
• Transcription mRNA forms from DNA code in the
  nucleus and moves to the ribosome
• Translation tRNA matches its anticodon to the
  codons on mRNA creating an amino acid chain.

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Transcription

1. One gene on the DNA strand unzips and is copied
   with RNA bases
2. Transcription begins at a promoter a sequence
   of bases that tells the RNA to begin binding.
3. When the DNA is transcribed, mRNA leaves the
   nucleus and goes to the ribosome for translation.

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Translation

• mRNA is translated into a protein
• mRNA arrives at the ribosome - 3 bases of mRNA
  1 codon (initiation)
• tRNA comes to the ribosome and the anticodon
  matches to the codon on mRNA (elongation)
• Amino Acids break off to form proteins
  (termination)

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Mutations

• An inheritable change in genetic code, which may
  or may not cause a change in the proteins made.

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• Deletion one or more base pairs are removed
  from the DNA sequence
• Example A T G G C A C C G A T T T A A with
  deletion A T G G C G A T T T A A

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• Insertion one or more base pairs are inserted
  into the gene sequence
• Example A T G G C A C C G A T T T A A A T G G
  C C A C A C C G A T T T A A

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• Base Pair Substitution - one or more base pairs
  are replaced with other base pairs
• Example A T G G C A C C G A T T T A A base pair
  substituted A T G G G G T C C G A T T T A A

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• ghs.gresham.k12.or.us/.../chpt14/chpt14.htm
• http//cnx.org/content/m12382/latest/dna.gif
• http//www.chemsoc.org/ExemplarChem/entries/2003/i
  mperial_Burgoine/replication.jpg
• http//fig.cox.miami.edu/cmallery/150/gene/c7.17.
  7b.transcription.jpg
• http//sps.k12.ar.us/massengale/images/584ELONGATI
  ON3.gif
• http//www.flyfishingdevon.co.uk/salmon/year3/psy3
  39evolutionarypsychologyroots/watson-crick-dna.jpg
  
• http//osulibrary.orst.edu/specialcollections/coll
  /pauling/dna/pictures/hersheychase1953.jpg