Part D: Translation/Protein Synthesis
RNA is produced in the nucleus of a cell and moves out of the nucleus to the cell’s ribosomes. This RNA is a
specific sequence of bases copied from the DNA which carries the genetic message to the cytoplasm. Thus,
it is called messenger RNA (mRNA). At the ribosomes, mRNA directs the building of proteins. Proteins are
made up of smaller molecules called amino acids. How does a cell construct the proper amino acids into
protein molecules? Formation of proteins involves another kind of RNA. Transfer RNA (tRNA) brings specific
amino acids to mRNA according to the code sequence of bases found on mRNA.
Open up your DNA strand to expose the mRNA strand that was created. Cut the mRNA strand
free from the DNA strand that it was created from and then glue your DNA strand back
together. This represents the mRNA leaving the nucleus. Let’s imagaine that the mRNA has
now traveled to a ribosome.
Tape the mRNA strand onto the left side of the pink paper. The pink paper represents the
cytoplasm.
Cut out the two tRNA molecules (cut only on solid lines).
1. How does the tRNA molecule
arrangement differ from the mRNA
molecule arrangement?
Join the tRNA to the mRNA strand in the correct order using base pairing rules.
What tRNA sequence will pair with each of the following mRNA sequences?
2. UUA
3. UCA
4. AAA
5. UGA
6. Messenger RNA carries the code in
7. Transfer RNA carries the code in
groups of three bases. What are these
groups of three bases. What are these
groups of three bases called?
groups of three bases called?
Cut out the two models of amino acids, glutamine and alanine
Match these amino acids to the correct tRNA molecules.
Using the chart, which amino acid connects to the following codons.
8. AGC
9. CUG
11. How many amino acids are associated
with one codon?
12. How many nucleotides make up one
codon?
Using the chart, which codon is needed to join with the following amino acids:
13. phenylalanine
14. tryptophan
15. methionine
16. Methionine is also known as the ____________________ codon.
Depending on the type and order of amino acids, an almost endless variety of proteins can be
produced. Because of the repeated matching of base sequences, the base sequence in the
DNA of chromosomes codes for and controls the formation of protein molecules at
ribosomes.
16. A protein molecule consists of the following
amino acid sequence :
leucine, glutamine, tyrosine, leucine, serine, serine
What would be the possible tRNA codons that could
code for leucine? Write down all possibilities.
17. A ribosome receives the following mRNA
message: AAA CGA GAA GUU
What would be the sequence of tRNA bases joining
the mRNA molecule?
18. What will be the sequence of amino acids
formed from this code? Remember that the amino
acid is based on the codon!
Now you should be able to transcribe a message in DNA into mRNA and then translate it into
a protein molecule.
19. Transcribe this message first into mRNA code, then translate it into tRNA code and proper
amino acid sequence.
DNA code
mRNA codons
tRNA
anticodons
Amino Acid
Sequence
AAT
GGG
ATA
AAA
GTT
20. Now rework the cell’s code backward by starting with the Amino Acid sequence.
Amino Acid
Sequence
Proline
Glutamic acid
Lysine
Serine
Leucine
tRNA
anticodons
GGA
CUU
UUU
UCA
AAU
21. What is the function of mRNA?
22. What is the function of tRNA?
23. Describe translation in your own words.
22. How many different stop codons are
there?
23. How many different amino acids are
there?
24. How many different codons are there?
mRNA codons
DNA code
Fill out the chart below with a yes or no in each box.
Similarities and Differences between mRNA and tRNA and DNA.
mRNA
Deoxyribose present
Ribose present
Phosphoric acid present
Adenine present
Thymine present
Uracil present
Guanine present
Cytosine present
Contains a chemical message
or code
Carries an amino acid to a
ribosome
Remains in the nucleus
Contains a codon
Contains an anticodon
tRNA
DNA