Question

Which one of the following pairs of codons is correctly matched with their function or the signal for the particular amino acid?
(a) GUU, GCU – Alanine
(b) UAG, UGA – Stop
(c) AUG, ACG – Start/Methionine
(d) UUA, UCA - Leucine

Answer 1

These are triplet of nucleotides sequence presence on mRNA, which terminates the method of translation and protein synthesis. These do not code for any amino acid.

Complete answer:
The genetic code contains the full information of the protein produced from RNA. It is the order of base pairs of amino acids that code for protein to be manufactured. Thus a change during this sequence can alter the formation of amino acids.
UAG, UGA – Stop is a pair of codons that are correctly matched with their function or the signal for the particular amino acid. There are three stop codons, which are UAG, UGA, and UAA. They are nonsense or terminating or stop codons as these are responsible for the termination of translation. They indicate the release of the nascent polypeptide from the ribosome because no like tRNA has anticodons complementary to those stop signals, enabling a release factor to bind to the ribosome rather. These do not code for any amino acid.

Additional information:
Alanine is an amino acid that's accustomed to make proteins. Coding DNA Strand Base Triplets of alanine are GCT, GCC, GCA, GCG.
The start codon is the principal codon of a messenger RNA (mRNA) transcript translated through a ribosome. The start codon constantly codes for methionine in eukaryotes. The most common start codon is AUG.
Leucine is a dietary amino alkanoic acid with the capacity to directly stimulate myofibrillar muscle protein synthesis. There are six different codons all of which can eventually produce a leucine within the protein chain. eg- CTC, CTA, and CTG.

So, the correct answer is ‘UAG, UGA – Stop’.

Note:
The Crick, Brenner, Barnett, and Watts-Tobin experiment first demonstrated that codons consist of three DNA bases. Marshall Nirenberg and Heinrich J. Matthaei were the first to reveal the character of a codon in 1961. The three stop codons have nicknames: UAG is amber, UGA is opal (sometimes also named umber), and UAA is ochre.