What distinguishes a coelomate animal from a pseudocoelomate animal
is that coelomates
A) have a body cavity, whereas pseudocoelomates have a solid body.
B) contain tissues derived from mesoderm, whereas pseudocoelomates have no such tissue.
C) have a body cavity completely lined by mesodermal tissue, whereas pseudocoelomates do not.
D) have a complete digestive system with mouth and anus, whereas pseudocoelomates have a digestive tract with only one opening.
E) have a gut that lacks suspension within the body cavity, whereas pseudocoelomates have mesenteries that hold the digestive system in place.
Silencers in eukaryotes control gene expression on a transcriptional level in which the mRNA is not transcribed. These DNA sequences may act as either silencers or enhancers based on the transcription factor that binds to the sequence and binding of this sequence will prevent promoters such as the TATA box from binding to RNA polymerase.  A repressor protein may have regions that bind to the DNA sequence as well as regions that bind to the transcription factors assembled at the promoter of the gene which would create a chromosome looping mechanism.  Looping brings silencers in close proximity to the promoters to ensure that groups of proteins needed for optimal gene expression will work together.
Regulation of transcription sometimes occurs via the simple presence or absence of transcription factors. An example of this is in the regulation of the immunoglobulin (an immune protein, also called antibody ) heavy chain gene, which is expressed in B lymphocytes (white blood cells that make antibodies) but not other cell types. This gene's enhancer (a region distant from the promoter) contains at least nine binding sites for regulatory proteins. The enhancer is acted on by activators present in B lymphocytes , while in nonlymphocyte cells repressors are present that inhibit transcription. This limits expression of the gene to lymphocytes.