[Campbell Biology P.424] A liver cell and a lens cell from the same organism express differe... | Practice Question

A liver cell and a lens cell from the same organism express different sets of genes, allowing them to perform specialized functions. Based on Figure 18.11 and the accompanying text, what is the most plausible molecular mechanism underlying this differential gene expression?

  • A: Different cell types contain distinct sets of RNA polymerases, which recognize different promoters.
  • B: Chromatin modification patterns are identical in all cell types, but the TATA box sequences vary.
  • C: Each cell type possesses a unique group of transcription activators that bind to specific combinations of control elements, leading to selective gene transcription.
  • D: Enhancers in different cell types physically move to different locations on the chromosome to activate distinct genes.
  • E: The DNA sequences of genes themselves differ between liver and lens cells, leading to different protein products.

Explanation

The text states: 'each cell type contains a different group of transcription activators.' This is the primary molecular basis for differential gene expression. Different combinations of activators binding to specific control elements lead to the selective transcription of different genes in different cell types, even though the DNA sequences are generally identical.