Final answer:
Cis-elements are DNA sequences that regulate gene expression on the same chromosome, while trans-factors are proteins and molecules that can influence gene expression by interacting with cis-elements.
Step-by-step explanation:
Cis-elements and trans-factors play crucial roles in the regulation of gene expression. Cis-elements are specific DNA sequences that are found on the same chromosome as the gene they regulate. These elements include promoters, enhancers, silencers, and other regulatory sequences that can be either proximal or distal to the gene they control. On the other hand, trans-factors refer to proteins or other molecules that can regulate gene expression but are not bound to the DNA. These factors include various transcription factors which bind specifically to cis-elements to either activate or repress the transcription of genes in response to different external stimuli. Enhancers are one type of cis-element that can significantly increase the transcription of a gene when bound by the appropriate transcription factors.
Option C is the correct answer: Cis-elements are regulatory sequences on DNA, while trans-factors are proteins or other molecules that regulate gene expression.