Radioactive adenosine is added to a medium where living mammalian tissue is cultured and the radioactive A gets incorporated into newly synthesised DNA. Which of the following types of chromatin is expected to be radioactive if cells are exposed to radioactive adenosine as soon as this enter the S phase? (Subtopic: Chromosome and Chromatin Structure)

As replication of DNA occurs in S-phase of cell cycle, DNA of both euchromatin and heterochromatin will undergo replication process and they take radioactive adenosine from the medium for the formation of complementary base pairs and hence, both chromatin will show Radioactive Adenosine. Heterochromatin is densely packed and deeply stained chromatin present in the periphery of nucleus responsible for regulation of gene expression due to position effect variegation. Euchromatin is loosely packed and lightly stained chromatin present in nucleus which contains almost 92% of human genome and undergoes transcription.