Suppose the mRNA being degraded in Figure 18.14 coded for a protein that promotes cell division in a multi-cellular organism. What would happen if a mutation disabled the gene for the miRNA that triggers this degradation?

miRNA are small single-stranded RNA (ribonucleic acid) molecules that are approximately 22 base pairs in length. These are produced from mRNA molecules by the action of cellular enzymes.

The function of the miRNA molecule is to base-pair with target mRNA and cause its degradation.

Any change in the nucleotide sequence in the DNA (deoxyribonucleic acid) is a mutation. Thus, the mutation affects and disables the gene. The disabled gene produces a defective or malfunctioning protein or a molecule.

The defective protein or molecule affects the functioning of the cell. As a result, mutations affect the proper functioning of the organisms and are involved in the development of cancer.

mRNA synthesized in the cell would be translated to a protein that is involved in cell division. However, when a defective miRNA is produced due to mutation, the miRNA would not base-pair with the target mRNA and would not be able to cause its degradation.

If the miRNA does not base-pair with the target mRNA, the mRNA would not be degraded. This would lead to the production of a protein that would continue to promote cell division.

As a result, unchecked cell division leads to the formation of a clump of cells called tumors that would ultimately lead to cancer development.