Control of gene expression takes place at the level of transcription, which is the process of synthesizing RNA from DNA template. Transcription is a highly regulated process that involves the binding of transcription factors and other regulatory proteins to specific DNA sequences, known as cis-acting elements, located in the promoter and enhancer regions of genes. The control of gene expression at the level of transcription involves various mechanisms that can enhance or repress transcription, such as:

1. Gene regulatory proteins: These proteins bind to specific DNA sequences and either activate or repress transcription. Examples of gene regulatory proteins include transcription factors, coactivators, and corepressors.

2. Epigenetic modifications: These modifications can alter the accessibility of DNA to transcriptional machinery, either by loosening or tightening the chromatin structure. Examples of epigenetic modifications include DNA methylation, histone modifications, and chromatin remodeling.

3. RNA processing: Alternative splicing, polyadenylation, and RNA editing can generate multiple mRNA isoforms from a single gene, which may have different stability, localization, and translation efficiency.

4. Regulatory RNAs: Non-coding RNAs, such as microRNAs and long non-coding RNAs, can regulate gene expression by binding to mRNAs and either repressing their translation or promoting their degradation.

In summary, the control of gene expression at the level of transcription is a complex process that involves the interplay of various regulatory mechanisms. Understanding these mechanisms is essential for developing treatments for diseases that result from dysregulated gene expression.

Transcription the process that converts genetic information from a DNA code into an mRNA code