Question

The term heterochromatin refers to heavily condensed regions of chromosomes that are largely devoid of genes. Since few genes exist there, these regions almost never decondense for transcription. At what point during the cell cycle would expect to observe decondensation of heterochromatic regions? Why?

Answer 1

The correct answer is: S phase.

Step-by-step explanation:

DNA can be divided into two functional forms: heterochromatin and euchromatin. Heterochromatin refers to the DNA that doesn't code for proteins or RNA, and thus it remains heavily condensed, for there would be no use to use it for transcription or translation. Euchromatin, on the other hand. is the DNA with the genes that can be transcripted into RNA and translated into proteins; for this reason, Euchromatin is less compact than Heterochromatin.

The only point in the cell cycle where Heterochromatin would be decondensed is S phase because, in this part of the cell cycle, the DNA gets replicated in order to prepare for Mitosis. For DNA to be replicated, it first needs to be decondensed to their two strands can be separated and used as guides for the synthesis of the two new strands.