A typical human cell expresses only about 5% of its genes at any time. The expression of a gene can be regulated during any step in the transition from a gene to a protein. In each step, there is a control point where the gene can be turned on or turned off. The gene expression can direct embryonic development during cellular differentiation in an embryo. The proteins responsible for the regulation are called

Enzymes

Explanation:

The regulation of gene expression is the central dogma of life. It is a series or set of mechanisms in which genetic information in the DNA expresses in the form of RNA or protein. Cells give gene expression b different mechanisms as transcription, maturation of mRNA, and translation.

During these mechanisms, different gene-regulatory proteins are influenced. For example, a set of RNA polymerases that are proteins transcribe the DNA molecule during transcription. Transcription factors are also proteins that control the synthesis of proteins in the cell. These proteins are an enzyme that catalyse the gene regulation in the human cells.

coal is not sustainable because it will one day run out.

chert is a sedimentary rock composed of microcrystalline or cryptocrystalline silica. with this little bit of information, you can come to the conclusion that your answer is c.  

explanation: