Question

Transfer RNA molecules are short RNA sequences (on average around 78 nucleotides long) that form a stem-and-loop structure, where one of the loops carries the anticodon that binds with the appropriate codon in the messenger RNA. At least 30 different tRNA genes are required by each cell to specify translation, but each of these tRNA genes can occur in multiple copies in a single genome, often co-located in clusters. How might these features of tRNA structure and function influence the way that tRNA genes evolve?

Answer 1

ANSWER :-

1. The t-RNA also termed as the transfer RNA plays a vital role in the process of translation by adding a specific amino acid to the m-RNA sequence transcribed from the DNA sequence and thus leading to synthesis of a peptide chain.
2. There are around 21 amino acids and more than 30 different t-RNA molecules specific for these amino acids. These genes are usually associated in clusters as can be seen in case of Prokaryotes and Eukaryotes.
3. Although, it should be taken into consideration that this tandem arrangement shows variations which are restricted in normal individuals. In simpler words, lets consider a healthy individual and an individual having cancer. Cancer is basically an output of replication error which results in the cell becoming immortal.
4. In normal individual, the copy number of the different t-RNA genes shows variations in terms of tandem repeats which restricts their interference with associated genes. In a person suffering from cancer, several studies have revealed that the tandem repeats are not linear or exceed the regulatory limit which leads to interference with certain promoters and associated elements resulting into mitotic instability which disturbs the functioning of gene and cell as a whole.
5. Clusters arrangement is also seen in certain Archael strains and along with the prokaryotes, the role is to ease cell growth. This basically acts as a device which regulates and promotes cell growth in individual, separate cells which are not dependent on external factors.
6. Although, in eukaryotic cells, variations can occur in one cell irrespective to other and this may lead to gene silencing in cases where a particular gene expression is not needed resulting in a kind of modification which may suggest evolution. Besides, the t-RNA genes modify depending upon the cellular requirement and functioning. The only criteria is the clusters should not I terfere with chromosomal gene functioning and this can be achieved by maintaining an appropriate tandem repeat and copy number variation. So, the variations are usually restricted to copy number and drive the synthesis of t-RNA molecules which are specific to carry out functioning of translational machinery. In simple words, according to the number of amino acid requirement for a particular activity, there will be variations in the copy number either leading to enhancement or decrease in expression of associated t-RNA molecules.

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