what are the drawbacks to only regulating at the transcriptional level and not the translational level or protein level?

Energy and Cellular Space

When gene Gene expression at (transnational level) is regulated it ensures energy and cellular space conservation, If a gene were to be regulated at each time after transcription, then significant amount of ATPs beyond the synthetic capacity of the cells will be needed, the cells will need large surface to accommodate the mechanism s. Thus regulation saves more energy and space to regulate gene expression. by turning on genes when needed to expressed and off when not needed.

Sequence of Gene

In addition, for the timely synthesis of exact copies of protein needed by the cells for various cellular activities; it is important for cells to regulate and control how the DNA is translated to the required proteins. If this mechanisms were not regulated deletion, addition of nitrogenous bases in gene sequence during translation may lead to mutations and therefore wrong coding of the needed protein in the cells.

Protein Quantity

Furthermore, the need to know the quantity of protein to synthesize, when to stop the synthesis, necessitated regulation of the process. If required amount is not expressed wrong amino acids units will be synthesized leading to abnormalities in hormones and enzymes.