Download Chapter 12

DNA & Protein
Synthesis
Vocabulary terms to learn:
gene
messenger RNA (mRNA) codon
ribosomal RNA (rRNA)
translation
transfer RNA (tRNA)
anticodon
transcription
RNA polymerase
DNA Replication
• Before a cell divides, it duplicates its DNA
1. Enzymes (DNA polymerase) “unzip” the
DNA molecule, breaking the hydrogen
bonds.
2. Each strand is now a template
3. New complimentary strands are produced.
DNA Replication
• Replicate the following
strand of DNA:
• ATTAGCTACTGC
• TAATCGATGACG
DNA
What is the difference?


DNA contains the
information for making
proteins, but it does not
make protein.
There are 3 forms of
RNA that are
responsible for using
the information stored in
DNA to make protein.
mRNA
rRNA
tRNA
What is RNA?
DNA
RNA & Protein Synthesis
• RNA – ribonucleic acid
–
–
–
–
Single polynucleotide chain
5 carbon sugar – ribose
No thymine; replaced with Uracil (A-U)
Assembles amino acids into proteins.
DNA vs mRNA
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
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DNA has
deoxyribose,
mRNA has ribose;
DNA has 2 strands,
mRNA has 1 strand;
DNA has thymine,
mRNA has uracil.
rRNA
tRNA
mRNA
messenger RNA
ribosomal RNA
transfer RNA
Protein Synthesis
• Transcription (DNA  mRNA)
– an RNA molecule is produced by copying part of the
nucleotide sequence of DNA
– Occurs in the nucleus
– RNA Polymerase
• Translation (RNA  Protein)
– Decoding of mRNA message
– Occurs in cytoplasm
– Uses all 3 forms of RNA
The Genetic Code
• Proteins are formed by joining amino acids into long
chains.
– There are 20 different amino acids
– the order in which they are arranged determines the
property of the protein.
• Codon – 3 consecutive nucleotides in RNA that
specifies for a specific amino acid.
– there are 64 possible codons
– Some amino acids are specified by more than one codon.
Types of RNA
1. Messenger RNA (mRNA)
•
•
Carries message from DNA (instructions for the
assembly of amino acids) from DNA to rRNA in
cytoplasm.
Every 3 N-bases = codon
2. Transfer RNA (tRNA)”
•
•
•
also known as anticodon (3 N-bases) complementary to
mRNA codons
Translates the message carried on mRNA codons into
amino acids. Fig.12-17 pg.303
Carries/transfers amino acids to ribosomes.
3. Ribosomal RNA (rRNA)
•
•
Makes up most of the ribosome
Site of protein synthesis- mRNA and tRNA come
together here
• RNA Sequence:
UCGCACGGU
• Codons:
– UCG CAC GGU
• Amino Acids:
– Serine – Histidine –
Glycine
Transcribe & Translate the following:
• TACCCTCAAGTAATT
• Transcribe: DNA  RNA
– AUGGGAGUUCAUUAA
• Translate: RNA  Protein
– Meth – Glyc-Val-Hist-STOP
DNA Translation


Translation assures that
the right amino acids
are joined together by
peptides to form the
correct protein.
The cell uses
information from mRNA
to produce proteins.
Transfer RNA (tRNA) The
Amino Acid Suppliers

Transfer RNA is part
of the process of
translation. It brings
the amino acid
coded for by mRNA,
and these amino
acids are joined
together to form
proteins.
Messenger RNA (mRNA):
The Genetic Blueprint
 Messenger RNA is a copy of the
genetic information that was
transcribed from the cell’s DNA.
 It is like a ‘blueprint’ of the
genetic information and is
brought to the ribosome and
translated into protein with the
help of tRNA.
Ribosomal RNA (rRNA) The Protein
Factories


Most of the RNA in cells is
associated with small
cellular structures known
as ribosomes, the protein
factories of the cells.
Ribosomes are the site of
Translation, where mRNA
arrives with genetic
instructions for building
proteins from amino acid
monomers brought by
tRNA.