A portion of a specific DNA molecule consists of the following sequence of nucleotide triplets:?

TAC GAA CTT CGG TCC

This DNA sequence codes for the following short polypeptide:

methionine - leucine - glutamic acid - proline - arginine

Describe the steps in the synthesis of this polypeptide. What would be the effect of a deletion or an addition in one of the DNA nucleotides? What would be the effect of a substitution in one of the nucleotides?

3 Answers

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  • 9 years ago
    Best Answer

    Describing the steps of translation of a mRNA is way too much to write here, you should look the steps of mRNA translation and write them down for that. This might help you

    http://www.youtube.com/watch?v=SghWl3MVbAI

    Youtube thumbnail

    &feature=fvw

    Now, the effect of a deletion, addition or substitution...

    Deletion: TAC GAC CTT CGG TCC -> Delete the first C -> TAG ACC TTC GGT CC... Do you see what happens? That sequence no longer codes for the same amino acids.

    Addition: TAC GAC CTT CGG TCC -> Add an A in the second codon -> TAC AGA CCT TCG GTC C... And again, the sequence no longer codes for the same amino acids, so the protein will change.

    Substitution: TAC GAC CTT CGG TCC -> Substitute the first G with a T -> TAC TAT CTT CGG TCC... In this case, only one amino acid will change (in some cases it doesn't even change because several codons code for the same amino acid).

    So.. which modification would be the most dangerous for you?

  • Scott
    Lv 4
    9 years ago

    1. Transcribe the DNA into mRNA 5'-GGA CCG AAG UUC GUA-3'

    2. Read mRNA at ribosome by attaching corresponding tRNA molecules for each codon. Each tRNA molecule will contain 1 anticodon as well as the corresponding amino acid. AUG is first codon to be translated (is always start codon) and always codes for methionine.

    CUU=leucine

    GAA=glutamic acid

    GCC=proline

    AGG=arginine

    3. Deletion would likely lead to a completely different peptide because it is a frameshift mutation. The reading frame gets shifted.

    4. Substitution can change the amino acid translated from a codon unless the substituted base is a base for which the codon still makes the same amino acid. This is why we call the codons degenerate. Multiple codons code for 1 amino acid

  • 4 years ago

    a) 1.- get the RNA sequence of each. 2.- get its anticodon. b) all the amino acids following the deleted or added nucleotide will change. c) the mutation can vary depending the location of the substitution; if it was the last nucleotide it can still make the same amino acid, but if it was the first it will entirely change the amino acid.

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