Transcription and Translation Work Sheet:



Transcription and Translation Exercise: Put names and answers on one sheet for group

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.

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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 Glycine-Gly. 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.

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1) Given the mRNA below, what protein would result if it was successfully translated by a ribosome?

a) Number of amino acids?_8_ b) Number of codons?_9 (including stop codon)_

c) Number of peptide bonds in protein?___7__ (one peptide bond between each pair of amino acids)

d) Find the start codon and show the amino acid sequence of the peptide resulting from translation of this mRNA.

5’-AGCCUUAUGAGGCAGGGGAUGACCGAGCGCUAAGGCCGG-3’

Protein translation(Met Arg Gin Gly Met Thr Glu Arg Stop!

2) The mRNA above was transcribed fro ma 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’-TCGGAATACTCCGTCCCCT ACTGGCTCGCGATT CCGGCC-5’

This is the ssDNA that was used to make the mRNA by the process of transcription.

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)

3’-TCGGAATACTCCGTC CCC TACTGGCT CGCGATTCCGGCC-5’ Original ssDNA

5’-AGCCTTATGAGGCAGGGGATGACCGAGCGCTAAGGCCGG-3’ Complimentary ssDNA

This is simply showing you how to make a new strand of DNA in semiconservative fashion.

Two complimentary ssDNA form a stable double helix

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?__4_ b) Number of codons?__5_ c) Number of peptide bonds in protein?__3___

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

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5’-AGCCUUAUGAGGCAGGGGAUGACCGAGCGCUAAGGCCGG-3’

Met Thr Glu Arg Stop codon

5) What additional types of RNA are required for translation to create a protein? (mRNA, tRNA and rRNA) What makes the endoplasmic reticulum “rough”? Presence of ribosomes on ER (endoplasmic reticulum). What organelle creates vesicles so that a protein can be transported to an extracellular destination by the process called exocytosis? Golgi Apparatus creates vesicles with the newly made proteins inside. The vesicles release contents to the outside of the cell when Exocytosis occurs.

6) 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

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(

Key to

Converting

Codons on

mRNA to

Amino Acid

Sequence

of protein

(

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