Final answer:
The pattern of gene expression is preserved through regulation at the level of transcription, maintaining DNA in a state ready for transcription, and environmental influences on gene expression. This selective expression conserves energy and space, and is essential for cell efficiency and function.
Step-by-step explanation:
To preserve the pattern of gene expression, several molecular mechanisms must be maintained. These include the maintenance of DNA in an accessible state for transcription, such as keeping it demethylated and acetylated. Regulation at the level of transcription ensures that genes are expressed only when necessary, which conserves energy and space within the cell.
Cells achieve efficiency by expressing only a subset of genes that are required for their specific function. For instance, cellular mechanisms are in place to ensure that genes are turned "on" or "off" depending on the cell's immediate needs. This is crucial as expressing all proteins at all times would require cells to be much larger and demand significantly more energy.
Furthermore, environmental conditions influence gene expression, indicating that while the genotype remains the same, the phenotypic expression can vary. Specialized drugs can also play a role in keeping the gene expression pattern intact by maintaining DNA in a state conducive for transcription of essential genes.
In summary, the regulation of gene expression, whether through internal cellular mechanisms or external factors, is essential for the processes and structures that support efficient cell function, and any errors in these regulatory processes can lead to diseases such as cancer.