Download Transcription and Translation Work Sheet:

Transcription and Translation Exercise:
Start Codon: AUG= starts a protein with the amino acid methionine
Stop Codon: UAG, UAA and UGA stop protein synthesis
Example: ACU= “A”1st base-“C”2nd base-“U”3rd base  Serthe amino acid THR or THREONINE
Example: UUG= “U” 1st base-“U” 2nd base- “G”3rd base  Leu the amino acid leucine
Assume the 5’ phosphate where the ribosome starts looking on mRNA for the start codon is on the left hand side of the
page and the 3’ hydroxyl end of the mRNA is on the right side.

Key to
Converting
Codons on
mRNA to
Amino Acid
Sequence
of protein
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Abbreviations for the 20 different amino acids: Phenylalanine-Phe, Leucine-Leu, Isoleucine-Ile, Methionine-Met,
Valine-Val, Serine-Ser, Proline-Pro, Threonine-Thr, Alanine-Ala, Tyrosine-Tyr, Histidine-His, Glutamine-Gin,
Asparagine-Asn, Lysine-Lys, Aspartate-Asp, Glutamate-Glu, Cysteine-Cys, Tryptophan-Tyr, Arginine-Arg, and GlycineGly. See your notes if you would like to see the structure of each amino acid and to review the structure of the peptide
bond that links adjacent amino acids in a protein.
-----------------------------------------------------------------------------------------------------------------------------1) Given the mRNA below, what protein would result if it was successfully translated by a ribosome?
a) Number of amino acids?__ b) Number of codons?_________
c) Number of peptide bonds in protein?________________________
d) Find the start codon and show the amino acid sequence of the peptide resulting from translation of this mRNA.
5’-AGCCUUAUGAGGCAGGGGAUGACCGAGCGCUAAGGCCGG-3’
2) The mRNA above was transcribed from a single strand of DNA that was unwound fro ma double helix. What was the
base sequence of this ssDNA? Remember: AT and GC and use Thymine instead of Uracil when converting back to DNA.
5’-AGCCUUAUGAGGCAGGGGAUGACCGAGCGCUAAGGCCGG-3’ Original mRNA
3) If a second strand of DNA was created (semiconservative replication) using the above strand of DNA as the template,
what would the sequence be? (Remember that the two single DNA strands are anti-parallel and held together as
complimentary base pairs across the alpha-helix by hydrogen bonds)
4) If you had a mutation on the original DNA such that the 7th nucleotide (Adenine) from the 5’-end was no longer present
in the mRNA, what would happen to translation?
a) Number of amino acids?___ b) Number of codons?___ c) Number of peptide bonds in protein?_____
d) Find the start codon and show the amino acid sequence of the peptide resulting from translation of this mRNA.
IF THIS “A” IS REMOVED, you no longer had the original start codon, the ribosome looks for the next one
↓
5’-AGCCUUAUGAGGCAGGGGAUGACCGAGCGCUAAGGCCGG-3’
5) What additional types of RNA are required for translation to create a protein? ________What makes the endoplasmic
reticulum “rough”?________________. What organelle creates vesicles so that a protein can be transported to an
extracellular destination by the process called exocytosis? ______________________
6) What is the significant difference with the structure and events that occur at the 5’ and 3’ ends of each ssDNA?
7) On the back show how a single cell with three pairs of homologous chromosome (3 types X 2 chromosomes/type = 6
dsDNA “chromosomes”) can divide to create two identical diploid cells by mitosis or four non-identical haploid cell by
meiosis. Use two colors to show how the single DNA strands were replicated semi-conservatively. Why do the
centromeres holding daughter chromatids together stay together until meiosis II in order to make haploid cells (gametes)?
For Help see your book and your Class Notes