Download protein synthesis - Ms. Dooley`s Science Class

PROTEIN SYNTHESIS
This activity will help you become more familiar with the process of protein synthesis
and will help distinguish between transcription and translation. Use your book to help
review any problems.
PART 1 - Transcription
During transcription, the DNA double helix “unzips”. As the hydrogen bonds between
the two strands break, nucleotides floating in the nucleus line up next to the nucleotides
of one DNA strand (“master strand”) to form mRNA. (Remember that uracil replaces
thymine in the RNA formation; therefore, uracil pairs with thymine and guanine pairs
with cytosine.) The nucleotides on the new mRNA are complimentary (opposite) to the
nucleotides in the master strand of DNA. After the mRNA is formed, it passes out of the
nucleus to go into the cytoplasm.
1. One strand of DNA has the base sequence: GCATTGGCAGTCATG. Write what the
strand of mRNA would like:
2. A strand of genetic code reads: CCATTGGATAA. Is this a strand of DNA or RNA?
How do you know?
PART 2 – Translation (I)
Once the mRNA has left the nucleus, it travels to a ribosome. There, the rRNA and
ribosome together read the mRNA in groups of three (codon). Each codon codes for a
specific amino acid (translation). the Genetic Code chart to decode the correct amino
acid for the following codons:
3. UUA:
11. GGG:
4. GAG:
12. CCA:
5. UAU:
13. GCU:
6. CUA:
14. AGA:
7. AUC:
15. GGG:
8. UUG:
16. UGG:
9. AAA:
17. UGU:
10. UUU:
PART 3 – Translation (II)
Once the ribosome reads the codon, an anticodon (tRNA) becomes attached to the
mRNA. The attachment of the tRNA to the mRNA continues until a termination (stop)
codon is read. At this point, the tRNA detaches and the protein chain of amino acids is
left. The tRNA goes back into the cytoplasm to pick up more amino acid. Determine
the tRNA (anticodon) for each codon below:
18. GGU :
20. AUG :
19. CGC:
21. AAA:
22. CUG :
Conclusions
23.
Write the mRNA that would be transcribed from the following strand of DNA:
GTA-TAC-CAG-TCA-TTT-GTC
24.
Using your answer from #23 (above), write the amino acid sequence which would
be translated:
25.
If there was a mistake in transcribing the DNA strand from #23 and the mRNA
read: CAA-AUG-GUC-AGU-AAA-CAG, how many mistakes were there made in
transcription?
26.
Using your answer to #25, what is the new amino acid sequence that would be
translated?
27.
What is a change in the genetic code called?