1.The same transcription factor can activate transcription of a gene in one cell type and repress transcription of the same gene in another cell type.How is this best explained? a.There are different DNA regulatory(response) elements for that gene in the two different cell types. b.There are different combinations of additional transcription factors present in the two cell types. c.The chromatin configurations at this gene locus are the same in two cell types. d.There are different posttranscriptional controls in the two cell types. 2.MicroRNAs a.are about 22 bases long. b.promote translation of their mRNA targets. c.evolved relatively recently. 3.In inducible systems a.the inducer interacts with the promoter. b.the repressor can never bind to the operator. c.the inducer allows transcription. 请问第一题是A吗? 感谢各位~ --

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