Combinatorial control refers to a regulatory mechanism in which: transcription requires a specific combination of transcription factors. each alternatively spliced transcript has a different combination of exons. none of the answer options is correct. transcription is initiated by a combination of sites in the promoter. transcription is terminated by a combination of sites in the terminator

The answer is;  transcription requires a specific combination of transcription factors

This allows the body to regulate a huge number of the gene with a small set of transcription factors. Using the analogy of combinatorial in mathematics, it is possible to have many combinations from a small set of numbers. This also applies in biology. Factors A and B in combination will regulate a different set of genes from factors A and C and factors B and C.

this protocol provides a detailed procedure for total protein extraction for western blot analysis from achieved samples following trizol isolation of rna.