Final answer:
The control of DNA replication is not considered a critical step in control of gene expression; it is a separate process. Gene expression regulation occurs mainly at the transcriptional stage in both prokaryotic and eukaryotic cells, with eukaryotes utilizing a complex system of transcription factors and DNA accessibility modifications.
Step-by-step explanation:
The statement that control of DNA replication is considered a critical step in control of gene expression is False. It is important to distinguish between DNA replication and gene expression processes. DNA replication is the process by which a cell duplicates its DNA, usually in preparation for cell division. On the other hand, gene expression involves the transcription of DNA into mRNA and the translation of mRNA into a functional protein. While control of DNA replication is crucial for accurate cell division and genomic integrity, the control of gene expression primarily occurs at the transcriptional level, particularly in eukaryotic organisms.
In both prokaryotic and eukaryotic cells, gene expression is a tightly regulated process. Prokaryotic cells predominantly regulate gene expression at the transcriptional stage, where factors control the binding of RNA polymerase to promote gene transcription. In eukaryotes, an array of transcription factors and additional regulatory proteins are involved in controlling the frequency and specificity of gene transcription. These transcription factors impact the binding of RNA polymerase to the DNA template strand, thus initiating the synthesis of RNA from DNA.
Additionally, eukaryotic cell gene expression can be regulated through modifications to histone proteins and DNA methylation, affecting the accessibility of DNA to transcription machinery. Overall, this regulatory process ensures cells synthesize necessary proteins at the proper time and place, which if disrupted can lead to diseases such as cancer.