July 25, 2012

Concerning protein synthesis

Protein synthesis is the process whereby DNA encodes for the production of amino acids and proteins. In this process what is a unit of three nucleotides on the mRNA called?

a) ribozyme
b) antiribozyme
c) base-pair
d) codon
e) anticodon

The correct answer is D

The coding mRNA sequence can be described as a unit of three nucleotides called a codon.

The ribosome binds to the mRNA at the start codon (AUG) that is recognized only by the initiator tRNA. The ribosome proceeds to the elongation phase of protein synthesis. During this stage, complexes composed of an amino acid linked to tRNA, sequentially bind to the appropriate codon in mRNA by forming complementary base pairs with the tRNA anticodon. The ribosome moves from codon to codon along the mRNA.

Amino acids are added one by one, translated into polypeptidic sequences dictated by DNA and represented by mRNA. At the end, a release factor binds to the stop codon, terminating translation and releasing the complete polypeptide from the ribosome.

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