Question

A scientist adds radioactive uridine to a culture of cells and examines an autoradiograph. Which type of chromatin is apt to· be labelled?

Options

• Heterochromatin

• Euchromatin

• Both Heterochromatin and Euchromatin.

• Neither Heterochromatin nor Euchromatin.

Answer 1

Euchromatin

Explanation:

Euchromatin is the loosely packed, transcriptionally active form of chromatin. Because it is “open,” RNA polymerase can access the DNA to synthesise RNA. When radioactive uridine (a precursor specific to RNA) is added, it is incorporated into the newly forming RNA strands primarily within these euchromatic regions. In contrast, heterochromatin is tightly packed and gene-silent, meaning little to no RNA synthesis occurs there to pick up the radioactive label.