Question

DNA exercises Ex. 1 Use the genetic code chart (Fig. 10.8A or the one in your LN) to translate the following mRNA sequences into amino acid sequences and answer the questions. mRNA nucleotide sequence (mRNA1) AUGGCAGACAAUAUUAAGUGA 1. What is the amino acid sequence? Mutation in the mRNA nucleotide sequence (mRNA2) AUGGCAGACCAUAUUAAGUGA 2. What is the new amino acid sequence? 3. How many bases were changed in mRNA2 compared to mRNA1? 4. What type of mutation was this? 5. How many amino acids changed? Mutation in mRNA nucleotide sequence (mRNA3 - compare to mRNA1) AUGGCAGACGAAUAUUAAGUGA 6. What is the new amino acid sequence? 7. How many bases were changed in mRNA compared to mRNA1? 8. What type of mutation was this? 9. How many amino acids were affected? 10. Which of the two mutations had the greatest effect and why?

Answer 1

DNA exercises ---

Ex. 1

Answer :

mRNA1 : AUGGCAGACAAUAUUAAGUGA

1. The amino acid sequence :

Met-Ala-Asp-Asn-Ile-Lys-STOP

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mRNA2 : AUGGCAGACCAUAUUAAGUGA

2. The amino acid sequence :

Met-Ala-Asp-His-Ile-Lys-STOP

3. 1 base was changed in mRNA2 compared to mRNA1.

A ---> C (Purine ---> Pyrimidine)

4. This is a kind of Point Mutation.

Transversion is a type of point mutation where purine changes into pyrimidine or pyrimidine changes into purine.

5. 1 amino acid has changed. (Asn ---> His).

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mRNA3 : AUGGCAGACGAAUAUUAAGUGA

6. The new amino acid sequence :

Met-Ala-Asp-Glu-Tyr-STOP

7. 1 base is added in mRNA3 compared to mRNA1.

8. It's a kind of Point Mutation. Addition or Insertion Mutation - When basepair adds into a codon.

9. 3 amino acids were affected.

10. mRNA3 mutation of the two mutations had the greatest effect because this mutation alter amino acids and termination codon is formed with in the genetic message that leads to formation of incomplete polypeptide.

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Ex. 2

Original DNA sequence :

TATGATACCCTGATAACTATCTGATTGCCG

1. The Complementary strand :

ATACTATGGGACTATTGATAGACTAACGGC

2. The mRNA strand :

AUACUAUGGGACUAUUGAUAGACUAACGGC

3. The tRNA anticodons for the mRNA strand :

UAU, GAU, ACC, CUG, AUA, ACU, AUC, UGA, UUG, CCG.

4. The amino acid sequence :

Ile-Leu-Trp-Asp-Tyr-STOP

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