Final answer:
Different combinations of transcription factors regulate gene expression by influencing RNA polymerase's ability to bind to DNA, affecting gene activation or repression. This regulation is crucial during development and in the prevention of diseases like cancer. Gene expression is controlled at multiple levels, including transcriptional and post-transcriptional.
Step-by-step explanation:
Different combinations of transcription regulators can control the expression of genes within cells. A small number of transcription factors can regulate a vast array of genes, affecting whether a gene is turned on or off, as well as the level of gene expression. These factors function through mechanisms that alter the binding affinity of RNA polymerase to specific promoters on the DNA, either as activators or repressors of transcription.
During development, transcription factors are critical in the orderly expression of genes, ensuring that proper cell differentiation and organ formation occur. For instance, in the development of primary sexual characteristics, the activity of transcription factors results in the differential expression of genes like slx, tra, dsx, and fru in Drosophila, leading to the manifestation of sex-specific traits.
Gene regulation is also important in preventing diseases such as cancer, which can arise from mutations in regulatory genes, particularly tumor-suppressor genes and proto-oncogenes. The regulation of gene expression is multi-faceted, including epigenetic, transcriptional, post-transcriptional, translational, and post-translational mechanisms.