Download Nucleic Acids & Protein Synthesis

Nucleic Acids &
Protein Synthesis
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.
Discovering the Code
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Fredrick Griffith used bacteria and mice to
first to theorize about the Genetic Code.
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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 Griffith’s
work to see if he could find the
transferring factor in Griffith’s experiment.
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Treated the bacteria with enzymes, each
destroying a specific structure of the cell.
When they destroyed DNA the experiment
didn’t work, proving DNA was the
transferring factor.
Discovering the Code
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DNA: is the nucleic acid that stores and transmits
the genetic information from one generation of
organisms to the next.
Hershey & Chase, Further tested Avery’s
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.
The Structure of DNA
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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.
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the sugar and the phosphate group make to backbone of
the chain
while the nitrogenous base sticks out.
Scientists and the Structure of
DNA
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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 Franklin’s 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.
Franklin’s D.N.A. X-ray
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.
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The Double Helix
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
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The Replication of DNA
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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.
The Replication of DNA
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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;
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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.
Replication
Replication results in
two DNA molecules
both of which are
identical to the
original.
The Structure of RNA
Is made of nucleotides.
 RNA is used to carry out the process of
Protein Synthesis.
 Three differences between RNA & DNA.
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The 5-carbon sugar in RNA is Ribose.
RNA is single stranded.
RNA contains a nitrogenous base called uracil
instead of thymine.
Types of RNA
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Three main types
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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.
Transcriptions
(RNA Synthesis)
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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.
RNA Editing
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Before the mRNA leaves the nucleus it
must be edited.
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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.
The Genetic Code
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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).
Translation
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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.