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PROTEIN
SYNTHESIS
CHAPTER 10 section 4
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Starting with DNA
• DNA ‘s code must be copied
and taken to the cytoplasm
• In the cytoplasm, this code
must be read so amino acids
can be assembled to make
polypeptides (proteins)
• This process is called
PROTEIN SYNTHESIS
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RNA Differs from DNA
• RNA has a sugar ribose
DNA has a sugar deoxyribose
•
RNA contains the base uracil (U)
DNA has thymine (T)
•
RNA molecule is single-stranded
DNA is double-stranded
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.
Three Types of RNA
• Messenger RNA (mRNA) copies
DNA’s code & carries the
genetic information to the
ribosomes
• Ribosomal RNA (rRNA), along
with protein, makes up the
ribosomes
• Transfer RNA (tRNA) transfers
amino acids to the ribosomes
where proteins are synthesized
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Protein Synthesis
 The production or
synthesis of proteins
happens in two phases:
Transcription & Translation
DNA  RNA  Protein
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Transcription
• During transcription, RNA polymerase enzyme binds to
a promoter on DNA and separates the DNA strands
• A promoter is a specific nucleotide sequence of DNA
where the RNA polymerase binds and starts
transcription.
• RNA Polymerase then uses one strand of DNA as a
template to assemble nucleotides into RNA
• Once the Polymerase reaches a terminal signal (the
stop sign), the RNA polymerase releases the RNA
and DNA
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The Genetic Code
• Three adjacent nucleotides
(letters) in mRNA codes for a
specific amino acid (word)
• A codon designates an amino
acid
• An amino acid may have more
than one codon
• There are 20 amino acids, but
64 possible codons
• Some codons tell the ribosome
to stop translating
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The Genetic Code
•Use the
code by
reading from
the center to
the outside
•Example:
AUG codes
for
Methionine
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http://learn.genetics.utah.e
du/content/molecules/tran
scribe/
Translation
• Translation is the process of decoding
the mRNA into a polypeptide chain
• Ribosomes read mRNA 1 codon at a
time and construct the proteins
• tRNA carrying the amino acid specified
by the codon binds and a peptide bond
is formed between the two amino
acids.
• This process continues until a stop
codon is reached.
• The ribosome then falls apart.
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Codons and Anticodons
• The 3 bases of an
anticodon are
complementary to
the 3 bases of a
codon
• Example: Codon ACU
Anticodon UGA
UGA
ACU
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http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter3/animatio
copyright cmassengale
12
n__how_translation_works.html
PROTEIN SYNTHESIS
ANIMATION
http://www.youtube.com/watch?
v=WgvnFYyJGZQ
http://www.youtube.com/watch?
v=itsb2SqR-R0
http://www.zerobio.com/drag_oa
/protein/overview.htm
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