Question

If the expression of every gene depends on a set of transcription regulators, then the expression of these transcription regulators must also depend on the expression of other transcription regulators, and their expression must depend on the expression of still other transcription regulators, and so on. Cells would therefore need an infinite number of genes, most of which would code for transcription regulators?

Answer 1

Transcriptional regulators function to regulate the expression of different genes and also to affect the expression of other transcriptional regulators, thereby the combination of a few transcriptional regulators is sufficient to modulate gene expression patterns

Step-by-step explanation:

Transcriptional regulators are able to control gene expression by binding to cis-regulatory elements on the genome. For example, in plants, MADS-box proteins are transcriptional regulators that contain an evolutionary conserved DNA-binding domain (i.e., MADS-box domain) which regulate simultaneously the expression of many different genes by binding to a conserved DNA motif called CArG box [CC(A/T)6GG] located in the promoter region of many genes expressed at specific stages of plant development. Within the cell, transcription regulators function not only by controlling the expression of different genes but also by affecting each other's activity, thereby creating different combinations where the expression of a limited number of transcription regulators is sufficient enough to regulate gene expression patterns.