Radioactive thymidine is fed to cells about to enter S-phase. It will make radioactive Euchromatin Heterochromatin Neither euchromatin nor heterochromatin Both A and B

Euchromatin is loosely packed DNA with higher gene concentration as compared to heterochromatin which is tightly packed and have less gene concentration, thus less DNA content. S phase includes replication of both euchromatin and heterochromatin DNA, the radioactive thymidine will be incorporated in both types of DNA. So, the correct answer is option C.