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Transcription and Translation
Inquiry into Life – pg. 493-501
Today’s Objectives:
 Demonstrate an understanding of the process of protein synthesis, including:
 Identify the roles of DNA, messenger RNA (mRNA), transfer RNA (tRNA), and ribosomes in the process of
transcription and translation, including initiation, elongation, and termination
 Determine the sequence of amino acids coded for by a specific DNA sequence (genetic code), given a table
of mRNA codons
 Identify the complementary nature of the mRNA codon and the tRNA anti-codon
DNA VS RNA
Both are nucleic acids made up of nucleotides.
DNA (Deoxyribonucleic Acid)
RNA (Ribonucleic Acid)
1.
2.
3.
4.
______________________________
Double stranded
______________________________
Bases:
A – Adenine
C– Cytosine
G – Guanine
T – Thymine
Sugar is ribose (5 carbon)
_____________________________
Found in nucleus and cytoplasm.
Bases:
__________________________
__________________________
__________________________
Introduction
*DNA ____________________ produces an __________________________________________________
*Protein synthesis _______________________________ to produce __________________.
Do not confuse these 2 processes!!!!!!
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DNA is the _____________________________ (or template) containing ____________ for the
________________________________________________. (structural and functional)
Proteins are __________________________________, but DNA never leaves the _________. A copy of the DNA
must be made. This copy is called _________________________ (mRNA). Only genes for required proteins are
copied into mRNA.
The process of making mRNA is called ____________________________.
mRNA travels into the cytoplasm where it is _______________________into proteins.
_________________________________________________________________
The nitrogenous bases in DNA contain the instructions for making proteins. _______________________
______________________________________________. Many amino acids make up a protein.
Each 3 base set is called a _____________________.
_________________________________________________________________
There are _____________possible combinations:
However, we only have about ____ amino acids, therefore most amino acids have more than 1 codon. Often the
codons only differ in the last base.
Example: CAA
CAG
_______________________________________________.
Duplicate codons may be a way of __________________________________________________. The duplication
of codons is called _______________________________.
The genetic code is basically “______________________.” The _____________________________________
_______________________________________. This suggests that all living things ______________________
____________________________________________.
AUG (Methionine) is a ______________________, whereas UAA, UGA and UAG are ____________________.
At the end of each mRNA strand there are long chains of ____________________ bases (Adenine Tail, poly-A
tail). ______________________________________________________________________________________.
When enough protein is created the adenine tail ________________. This tells the body that this particular
mRNA is _____________________________ to produce its protein. The cell will then digest the no longer
functional m-RNA (lysosomes will be involved in this process).
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Types of RNA
mRNA – Messenger RNA
tRNA – Transfer RNA
rRNA – Ribosomal RNA
PROTEIN SYNTHESIS
Transcription
• The first step of protein synthesis is called transcription.
• Transcription is the _________________________________________________________________.
• Only RNA can _______________________.
A. The gene in DNA is ________________________________________________ by enzymes. The gene
codes for the ___________________that will be eventually produced.
B. The gene is then _____________by enzymes. (H bonds broken between bases)
C. Free – floating _____________________ join complementary to the selected gene.
This DNA strand is called the _______________________________.
**Uracil joins to adenine always in RNA. There is no ________________in RNA**
D. The Ribose –phosphates join together to complete the backbone. The
_______________________ that is temporarily formed breaks by enzymes and is pulled
__________________________________________________________.
We now have an mRNA strand. Steps A, B, C and D= Transcription
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E. mRNA is released (Enzymes break the Hydrogen bonds). DNA ________________ back together.
mRNA is first processed (_________________________________________________________) so it can
leave the nucleus then passes through the _________________________ through the nuclear pores into the
cytoplasm.
F. DNA recoils back up into its ___________________________ with the help of enzymes.
Translation
• The second step in protein synthesis is called translation.
• Translation is the process of ________________________________________________________
_________________________________________________________________________ (protein).
It occurs in 3 steps.
• Translation occurs at ________________________. (cytoplasm or RER)
G. Step 1 – Initation. mRNA becomes associated with a ribosome which are made up of
ribosomal RNA (rRNA) and proteins.
When the mRNA comes near the two subunits, the large one ___________________ the
mRNA in the smaller one.
H. The ribosome reads the first codon (______________________________________).
tRNA contains a set of bases which are complementary to the bases on the mRNA. tRNA bases
are called _______________. The ribosome bonds the _____________________________.
I.
Step 2 – Elongation. The ribosome moves to the next __________. A complementary
tRNA arrives with an amino acid and joins to the mRNA codon. The A.A. from the first tRNA is joined to
the A.A. on the new tRNA. The first tRNA is released and goes off to find another identical amino acid.
J.
Step 3 – Termination. The ribosome continues to read the mRNA and the
______________________________ chain grows until a _________________________
is reached. The finished polypeptide is released.
The mRNA will disintegrate or be read by more ribosomes. (mass production of identical proteins)
Many ribosomes may be found together, ______________________________________.
This group of ribosomes is called a ____________________________________.
The maximum number of tRNA on a ribosome at one time is ____________.
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Summary of Protein Synthesis
IF the DNA strand is TACTTATGCTCCTAAATT
1. What are the codons on the mRNA strand?
2. What is the sequence of amino acids produced?
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Sketch and label the process of transcription and translation – Try to work from your memory!