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Protein Synthesis
DNA
&
RNA
DNA
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Deoxyribonucleic Acid
Shape - double helix - twisted ladder
DNA cont.
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Made up of three parts
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A sugar molecule - deoxyribose
A phosphate group
A nitrogen base
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Adenine
Guanine
Cytosine
Thymine
Bases
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Purines - 2 rings of carbon and nitrogen
atoms
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Adenine
Guanine
Pyrimidines - 1 ring of carbon and nitrogen
atoms
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Thymine
Cytosine
Purines
Complementary Base Pairing
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Nucleotides that normally pair together
2 Base-pairing rules
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Cytosine bonds with guanine
Adenine bonds with thymine
Base pairs connect by hydrogen bonds
The DNA Song to the tune of "Row, Row,
Row your Boat
We love DNA, made of nucleotides.
Sugar, phosphate and a base bonded
down one side.
Adenine and thymine make a lovely
pair,
cytosine without guanine would feel
very bare.
Replication of DNA
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Replication= process of copying DNA in the
cell.
1. Two nucleotide chains are separated by
helicase enzyme. (AKA replication fork)
2. Hydrogen bonds within DNA are broken.
3. DNA polymerases attached to strands.
4. Complimentary DNA strands are formed.
5. New strands bind with old strands resulting
in two full strands of DNA.
RNA

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Ribonucleic Acid
Shape - Single helix
RNA
Three Type of RNA
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Messanger RNA (mRNA)
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Transfer RNA (tRNA)
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Carries genetic material from DNA in the nucleus
to the cytosol.
Hairpin shaped.
Binds directly to amino acids.
Ribosomal RNA (rRNA)
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Most abundant type of RNA
Assist in production of proteins
RNA cont.
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Made up of three parts

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A sugar molecule - ribose
A phosphate group
A nitrogen base
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Adenine
Guanine
Cytosine
Uracil
Purine or Pyridimine?
Pyridimine
Complementary Base Pairing
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2 Base-pairing rules
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Cytosine bonds with guanine
Adenine bonds with URACIL
General Information
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One strand of the DNA double helix is used as a
template
DNA is only found in the nucleus
Protein synthesis takes place in ribosomes.
Breaking the Bonds
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RNA polymerase bumps into the promotor site of the
DNA
Helicase is an enzyme used to unzip the DNA
Occurs inside the nucleus!
Breaking the Bonds cont.
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Messenger RNA
(mRNA) is synthesized
by RNA polymerase
until a stop signal is
reached.
After mRNA is Made
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Helix zips the DNA molecule as hydrogen
bonds form
mRNA leaves the nucleus
mRNA
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mRNA leaves the nucleus through pores in the
nuclear membrane and travels to the cytoplasm
Every 3 bases make what is known as a codon
Look on page 195 of text
2
n
d
1st
3rd
Something to notice
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There is only one start codon.
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For translation to occur, mRNA must have AUG.
There are three stop codons.
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Translation will stop if mRNA reaches UAA, UAG
or UGA.
Translation
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Ribosomes bind with the
mRNA at the start codon
(AUG)
tRNA (transfer RNA) has an
anticodon (three nitrogenous
bases that are
complementary to the codon
on mRNA) that codes for
the same amino acid.
Translation cont.
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tRNA finds the amino acid that the genetic code asks
for and bring it to the ribosomes.
Translation
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What would the tRNA sequence be?
Translation cont.
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The ribosomes build peptide bonds connecting the
amino acids to form a polypeptide.
Protein Elongation
Ending Translation
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At the end, the stop codon terminates translation
The complete polypeptide is released from the
ribosome.
Termination of Translation
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What would the peptide sequence be?
Summary of Translation
Proteins Synthesis
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DNA is “unzipped”
mRNA is made and leaves the nucleus
tRNA takes the amino acids to the ribosomes
Protein is made