How many types of biofuels are there?

In principle, how many different cell types can an organism having four different types of transcription regul?

• In principle, how many different cell types can an organism having four different types of transcription regulator and thousands of genes create? A. thousands B. up to 4 C. up to 16 D. up to 8 E. ten-of-thousands The expression of the BRF1 gene in mice is normally quite low, but mutations in a gene called BRF2 lead to increased expression of BRF1. You have a hunch that nucleosomes are involved in the regulation of BRF1 expression and so you investigate the position of nucleosomes over the TATA box of BRF1 in normal mice and in mice that either lack the BRF2 protein (BRF2–) or part of histone H4 (HHF–) (histone H4 is encoded by the HHF gene). Your results are summarized below. A normal functional gene is indicated by a plus (+). Mouse Nucleosome positioning Relative level of BRF1 mRNA BRF2+ HHF+ specific pattern 1 BRF2– HHF+ random 100 BRF2+ HHF– random 1 BRF2– HHF– random 100 Which of the following conclusions CANNOT be drawn from your data? A. none of these. B. The specific pattern of nucleosome positioning over the BRF1 upstream region is required for BRF1 repression. C. BRF2 is required for the specific pattern of nucleosome positions over the BRF1 upstream region. D. The part of histone H4 missing in HHF– mice is not required to form nucleosomes. E. BRF2 is required for repression of BRF1.

• Answer:

  The answer to the first question depends on what exactly you mean by "different type" of regulator. If these are 4 off-on switches that can be independently switched the answer is 16, unless you can somehow have different regulators in different cells for the same gene (very unlikely). If "different type of regulator" includes selfinhibinting regulators or other sophisticated regulators the answer is tens-of-thousands.