protein synthesis vấn đề dịch mã

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PROTEIN
PROTEIN
SYNTHESIS
SYNTHESIS
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DNA
DNA
and
and
Genes
Genes
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DNA
DNA
•
DNA contains genes,
sequences of nucleotide
bases
•
These Genes code for
polypeptides (proteins)
•
Proteins are used to build
cells and do much of the
work inside cells
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Genes & Proteins
Genes & Proteins


Proteins are made of
amino acids linked
together by peptide
bonds

20 different amino acids
exist
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Amino Acid Structure
Amino Acid Structure
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Polypeptides
Polypeptides
•
Amino acid
chains are
called
polypeptides
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7
DNA Begins the Process
DNA Begins the Process
•
DNA is found inside the
nucleus
•
Proteins, however, are made
in the cytoplasm of cells by

organelles called ribosomes
•
Ribosomes may be free in the
cytosol or attached to the
surface of rough ER
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Starting with DNA
Starting with DNA
•
DNA ‘s code
DNA ‘s code
must be
must be
copied
copied


and taken to the cytosol
and taken to the cytosol
•
In the cytoplasm, this
In the cytoplasm, this
code
code
must be read
must be read
so
so
amino acids

amino acids


can be assembled to make
can be assembled to make
polypeptides (proteins)
polypeptides (proteins)
•
This process is called
This process is called
PROTEIN SYNTHESIS
PROTEIN SYNTHESIS
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RNA
RNA
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Roles of RNA and DNA
•
DNA is the MASTER
PLAN
•
RNA is the
BLUEPRINT of the
Master Plan
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11
RNA Differs from DNA
RNA Differs from DNA
•

RNA has a sugar
RNA has a sugar
ribose
ribose
DNA has a sugar
DNA has a sugar
deoxyribose
deoxyribose
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Other Differences
Other Differences
•
RNA contains the
RNA contains the
base
base
uracil (U
uracil (U
)
)
DNA has
DNA has
thymine
thymine
(T)
(T)
•
RNA molecule is
RNA molecule is

single-stranded
single-stranded
DNA is
DNA is
double-
double-
stranded
stranded
DNA
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Structure of RNA
Structure of RNA
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.
Three Types of RNA
Three Types of RNA
•
Messenger RNA (mRNA)
Messenger RNA (mRNA)
copies
copies
DNA’s code & carries the
DNA’s code & carries the
genetic information to the
genetic information to the
ribosomes
ribosomes
•

Ribosomal RNA (rRNA)
Ribosomal RNA (rRNA)
, along
, along
with protein, makes up the
with protein, makes up the
ribosomes
ribosomes
•
Transfer RNA (tRNA)
Transfer RNA (tRNA)
transfers
transfers
amino acids to the ribosomes
amino acids to the ribosomes
where proteins are synthesized
where proteins are synthesized
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15
Messenger RNA
•
Long Straight chain
of Nucleotides
•
Made in the Nucleus
•
Copies DNA & leaves
through nuclear
pores
•

Contains the
Nitrogen Bases A, G,
C, U ( no T )
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Messenger RNA (mRNA)
Messenger RNA (mRNA)
•
Carries the information for a
Carries the information for a
specific protein
specific protein
•
Made up of
Made up of
500 to 1000
500 to 1000
nucleotides long
nucleotides long
•
Sequence of 3 bases called
Sequence of 3 bases called
codon
codon
•
AUG
AUG
– methionine or
– methionine or
start

start
codon
codon
•
UAA, UAG, or UGA
UAA, UAG, or UGA
–
–
stop
stop
codons
codons
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Ribosomal RNA (rRNA)
Ribosomal RNA (rRNA)
•
rRNA is a single
rRNA is a single
strand
strand
100 to 3000
100 to 3000
nucleotides
nucleotides
long
long
•
Globular
Globular

in shape
in shape
•
Made inside the
Made inside the
nucleus
nucleus
of a cell
of a cell
•
Associates with
Associates with
proteins to form
proteins to form
ribosomes
ribosomes
•
Site of
Site of
protein
protein
Synthesis
Synthesis
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18
The Genetic Code
•
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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19
The Genetic Code

•
Use the
code by
reading from
the center to
the outside
•
Example:
AUG codes
for
Methionine
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Name the Amino Acids
•
GGG?

•
UCA?
•
CAU?
•
GCA?
•
AAA?
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Remember the
Remember the
Complementary Bases
Complementary Bases
On DNA:
A-T
C-G
On RNA:
A-U
C-G
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Transfer RNA (tRNA)
Transfer RNA (tRNA)
•
Clover-leaf shape
•
Single stranded molecule with
attachment site at one end
for an amino acid

•
Opposite end has three
nucleotide bases called the
anticodon
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Transfer RNA
Transfer RNA
amino acid
amino acid
attachment site
attachment site
U A C
anticodon
anticodon
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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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Transcription
Transcription
and
and
Translation
Translation
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