Although a single activator may bind many enhancers in the genome to control several target genes, in many cases, the enhancers have some sequence conservation but are not all identical. Keeping this in mind, consider the following hypothetical example:

- Undifferentiated cells adopt different fates depending on the concentration of activator protein, Act1.
- A high concentration of Act1 leads to cell fate 1, an intermediate level leads to cell fate 2, and low levels to cell fate 3.
- Research shows that Act1 regulates the expression of three different target genes (A, B, and C) with each having an enhancer recognized by Act1 but a slightly different sequence that alters the affinity of Act1 for the enhancer. Act1 has a high affinity for binding the enhancer for gene A, a low affinity for the gene B enhancer, and an intermediate affinity for the gene C enhancer.

From these data, speculate on how Act1 concentrations can specify different cell fates through these three target genes? Furthermore, which target genes specify which fates?

Video transcript

Hello everyone and welcome to today's video. So we have a gene called TP 53 is a gene responsible for the production of a protein called a tumor protein. P 53. This protein is a tumor suppressor. So it's going to prevent tumors and can regulate cell division and keeps it from growing uncontrollably. How will they respond if the DNA damage Is irreparable? So normally these p. protein which by the way it's called the Guardian of the cell because it is going to protect it against tumors or mutations of DNA. So when this DNA damage is irreparable, this protein is going to signal the repair of the D. N. A. However in the question it states that the DNA cannot be repaired. So instead this protein is going to signal the cell to undergo apoptosis or basically kill the cell to prevent these mutation from spreading once the cell divides. So P. T. T. Three is going to prevent completely this cell division, it is not going to slow it down. It is going to completely prevent it to prevent the spread of this tumor to prevent the growth of the tumor. That can come from uncontrollable cell division and instead it is just going to signal the cell to undergo apoptosis and by doing so it will kill the cell. So the correct answer choice here is going to be answer choice B. This is what's done once DNA damage in the cell is irreparable. I really hope this video helped you and I hope to see you on the next one