Download Section 11.2 Summary – pages 288

BELLRINGER: 10-31-10
Draw the following box and fill in the squares,
THIRD box on the last bell-ringer page:
REPLICATION
Where in the cell does this take place?
TRANSCRIPTION
Where in the cell does this take place?
What is created in this process?
What is created in this process?
When does this take place?
WHY does this take place?
THE THREE TYPES OF
RNA
• There are three types of RNA that help build proteins.
# 1 Messenger RNA (mRNA)
brings instructions from DNA in the nucleus to the
cytoplasm.
Then mRNA binds to ribosomes.
#2
Transfer RNA (tRNA) is the supplier.
Transfer RNA delivers amino acids (the building
blocks of proteins) to the ribosome to be assembled
into a protein.
Amino Acid
How it binds with mRNA
#3
Ribosomes are made of Ribosomal RNA (rRNA).
rRNA uses the instructions from mRNA and the
supplies from tRNA to assemble the amino acids in
the correct order.
• mRNA brings the instructions.
• tRNA supplies the amino acid parts.
• rRNA builds the proteins using the instructions
and amino acids.
RIBOSOME
THE PROCESS OF
TRANSLATION
During Transcription, mRNA is made.
The copy of instructions for making proteins on
an mRNA strand is in the form of a code.
The Genetic Code
• Every three letters on a mRNA
strand, called a codon, is a
code for a specific amino acid
(a building block to make
protein)
There are thirty different kinds of amino
acids.
Different types of proteins are made with
amino acids in different sequences
• The codons on a mRNA strand need to be converted
into amino acids.
mRNA
codons
Amino
Acids
• The process of converting the codons on mRNA into a
sequence of amino acids to make a protein is known
as translation.
Every three letters on an mRNA
strand is a codon.
Each codon codes for a specific
amino acid.
CODON CHART
The Genetic Code
• Sometimes there are several codons that code for the
same amino acid….for instance,
What two codons code for the amino acid “Arg”
(Arginine)?
Below is a DNA strand….
During Transcription, what mRNA strand would be made
from this DNA?
TAC C C G TAT T C GAAG G C T
AU G G G CAUAAG C U U C C GA
Methionine
Glycine
Isoleucine
Serine
Phenylalanine
Arginine
Using this mRNA strand, translate the codons into amino
acids using your codon chart.
THIS IS WHAT
TRANSLATION
LOOKS LIKE
Why does mRNA have to be made?
(Why can’t DNA deliver it’s own instructions)
Nucleus
Where does mRNA take the instructions so that
proteins can be made?
• Translation takes place at the ribosomes (rRNA)
of a cell.
Translation from mRNA to
Protein
• mRNA brings the codons (message) from DNA to the
ribosome (rRNA)
mRNA
Coming from
Nucleus
RIBOSOME
Step 1
• As translation begins, one end of mRNA strand
attaches to a ribosome.
mRNA strand
Ribosome
Translation from mRNA to
Protein
• tRNAs bring amino acids to the ribosomes.
mRNA
Coming from
Nucleus
RIBOSOME
Amino
acid
• Each tRNA only
carries one amino
acid.
• There are also three nucleotides on the bottom of the
tRNA called an anti-codon.
• Anti-codons complementary base pair with the codons
on mRNA.
(this is to make sure they are bringing the correct amino acidIf the anti-codon doesn’t base pair with the codon, then the
wrong amino acid was brought)
Anti-codon
• AUG is usually the first codon on the mRNA strand.
• This signals the ribosome to START making a protein.
Methionine
• A tRNA with anticodon UAC comes and binds with this
codon and drops off it’s amino acid “Methionine”.
• After the first tRNA binds with its codon, the
mRNA slides down so that the ribosome can read the
next codon.
• A new tRNA molecule carrying an amino acid pairs
with the second mRNA codon.
Alanine
• The amino acids then bond together.
• Once the first tRNA lets go of it’s amino acid, it is
released from the ribosome.
Methionine
Alanine
bond
• A chain of amino acids is formed until the
stop codon is reached on the mRNA strand.
The end result
is a protein
Stop
codon