Nucleic Acids

1
Nucleic Acids Protein Synthesis
2
The Genetic Code

• Biologists call the program of the cell the
  genetic code.
• The Genetic Code, is the way in which cells store
  the program that they need to pass from one
  generation to the next.

3
Discovering the Code

• Fredrick Griffith used bacteria and mice to first
  to theorize about the Genetic Code.
• Proves that information from one strain is being
  transferred to the other strain thus proving
  there is a transferring factor.
• Oswald Avery decided to repeat Griffiths work to
  see if he could find the transferring factor in
  Griffiths experiment.
• Treated the bacteria with enzymes, each
  destroying a specific structure of the cell.
• When they destroyed DNA the experiment didnt
  work, proving DNA was the transferring factor.

4
Discovering the Code

• DNA is the nucleic acid that stores and
  transmits the genetic information from one
  generation of organisms to the next.
• Hershey Chase, Further tested Averys
  conclusion, using viruses called a bacteriophage.
• Bacteriophage- Made of DNA and a protein coat
  (covering).
• They labeled the two parts of the bacteriophage
  with radioactive isotopes.
• They found the radioactive material used to label
  DNA inside the bacteria, proving that the DNA was
  the transferring factor.

5
The Structure of DNA

• DNA is made of units called nucleotides.
• Nucleotides are made up of a 5-carbon sugar
  (deoxyribose), a phosphate group, and a
  nitrogenous base.
• Nitrogenous bases are Adenine, Guanine,
  Cytosine, and Thymine.
• Adenine and Guanine are Purines.
• Cytosine and Thymine are Pyrimidines.
• Individual nucleotides are joined together to
  make D.N.A.
• the sugar and the phosphate group make to
  backbone of the chain
• while the nitrogenous base sticks out.

6
Scientists and the Structure of DNA

• Rosaliand Franklin Maurice Wilkins tried to
  use x-ray beams to determine the structure of
  DNA.
• At the same time as Franklin Wilkins two other
  scientists name James Watson and Francis Crick
  were also trying to determine the structure of
  DNA.
• Watson Crick, using Franklins X-ray pattern,
  built a 3-dimensional model of DNA, the model was
  made of two strands twisted or spiraled around
  each other, they called this shape a Double Helix.

7
Franklins D.N.A. X-ray
8
The Double Helix

• In the double helix the nitrogenous bases are
  positioned exactly opposite each other.
• This positioning allows for a weak Hydrogen bond
  to from between Adenine(A) Thymine(T), and
  Cytosine(C) Guanine(G).
• Base Pairing is the force that hold the two
  strands of the DNA double helix together.

9
The Double Helix
10
DNA and the Chromosome

• In eukaryotes the chromosome contains both DNA
  and proteins, they are packed tightly together to
  form a chromatin.
• Chromatin consists of DNA that is tightly packed
  around a protein called histone

11
The Replication of DNA

• The two strand in the double helix are
  complementary.
• Complementary means that they have all the
  information necessary to reconstruct the other
  strand.
• Each strand of DNA serves as a template against
  which a new strand can be made.
• Before a cell divides it must copy DNA to ensure
  that each new cell has a complete set of DNA.
• The process of copying DNA is known as
  replication or DNA synthesis and is carried out
  by enzymes.

12
The Replication of DNA

• Enzymes separate the two strands of DNA by
  breaking the H bonds of the base pairs.
• The main enzyme of replication is DNA Polymerase
• The enzymes
• 1.) Separates the strands.
• 2.) Reads the strands.
• 3.) Insert the appropriate (complementary) base.
• 4.) Produce the sugar-phosphate backbone.
• 5.) proofreads the bases to make sure they are
  correct.
• Example If a strand reads T-A-C-G-T-T it will
  produce the strand
  A-T-G-C-A-A and vice versa.

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Replication
Replication results in two DNA molecules both of
which are identical to the original.
14
The Structure of RNA

• Is made of nucleotides.
• RNA is used to carry out the process of Protein
  Synthesis.
• Three differences between RNA DNA.
• The 5-carbon sugar in RNA is Ribose.
• RNA is single stranded.
• RNA contains a nitrogenous base called uracil
  instead of thymine.

15
Types of RNA

• Three main types
• Messenger RNA (mRNA) carries copies of
  instructions to assemble proteins.
• Ribosomal RNA (rRNA) found in at the ribosome, is
  the site of protein construction.
• Transfer RNA (tRNA) transfers amino acids to the
  ribosome where they are assembled into protein.

16
Transcriptions (RNA Synthesis)

• Transcription- Process by which RNA is produced
  by copying part of the sequence of DNA into a
  complimentary sequence in RNA.
• Transfers information from DNA to RNA.
• RNA Polymerase- Enzyme used in transcription to
  make RNA from DNA.
• RNA polymerase binds to regions of DNA called
• promoters - Base sequences that signal where in
  the DNA the polymerase should bind.
• The polymerase creates the complimentary strand
  of mRNA .
• mRNA carries information from DNA to the ribosome
  to create proteins.

17
RNA Editing

• Before the mRNA leaves the nucleus it must be
  edited.
• DNA contains sequences of nucleotides called
  introns (not used in protein synthesis) and exon
  (are used in protein synthesis).
• When the RNA is made it contains both.
• Before the mRNA leaves the nucleus, it is edited
  to remove the introns.

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The Genetic Code

• The language of the mRNA.
• It is written using four different letters in
  combinations of 3 letters at a time.
• These different 3 letter combinations are called
  codons. Each codon specifies a single amino acid
  that is to used to form the protein chain.
• The codons can be decoded using a chart.
• There is a start codon that begins protein
  synthesis (AUG), and three that stop it (UGA,
  UAA, UAG).

19
Translation

• Translation-The decoding of mRNA to make protein.
• Starts when mRNA reaches the Ribosome.
• As mRNA moves through the ribosome the codons are
  decoded.
• tRNA then brings the amino acid specified by the
  codon to the ribosome.
• At the ribosome the amino acids are assembled to
  make the protein.
• Each tRNA carries a specific amino acid, and has
  three unpaired bases called anticodons which are
  complimentary to a codon.