Anonymous
Anonymous asked in Science & MathematicsBiology · 8 years ago

Help with Nucleotide Triplets?

A portion of a specific DNA molecule consist 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 effects of a deletion or an addition in one of the DNA nucleotides? What would be the effect of a substitution of one of the nucleotides?

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  • Best Answer

    First of all, DNA Sequence:-

    TAC GAA CTT (G)GG TCC (that was a mistake in your question)

    Now DNA gets transcribed to mRNA according to the rule of complimentary base pairing:-

    mRNA Sequence:-

    AUG CUU GAA CCC AGG

    Now, you have to look up the Codon Chart to find out the Amino Acids coded by each Codon.

    Click the link mentioned in the source.

    Amino Acid Sequence:-

    methionine- leucine- glutamic acid- proline- arginine

    Deletion or addition of the nucleotides in the *multiples of 3* causes the deletion or addition of some amino acids in the polypeptide respectively, while deletion or addition of the nucleotides in the *non-multiples of 3* would result in a 'shift of the triplet sequence' of the codons changing the entire polypeptide from the point where mutation occurs.

    Example:-

    RAM HAS RED CAP

    Suppose these are the bases of the DNA.

    If i insert B, then I, then G, in between the HAS and RED, it would change the triplet sequence.

    RAM HAS BRE DCA P (← whole triplet sequence is disturbed)

    RAM HAS BIR EDC AP (← whole triplet sequence is disturbed)

    RAM HAS BIG RED CAP. (←BIG- multiple of 3 causes an amino acid to be added)

    This is called as frame shift mutation

    Substitution of a nucleotide causes a point mutation and results in the change of a single amino acid in the polypeptide. An example is Sickle Cell Anemia where a point mutation causes the change in the β-polypeptide chain of haemoglobin molecule.

  • Anonymous
    8 years ago

    > This DNA Sequence codes for the following short polypeptide: methionine

    No it doesn't.

    Your teacher has failed to teach you directionality of DNA.

    Have your teacher mark the 5' and 3' ends. Science is about describing things better. Your teacher failed.

  • Cheryl
    Lv 4
    4 years ago

    Assembly takes place at the ribosome. Is this what you were thinking of?

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