Which of the following statements correctly distinguishes euchromatin from heterochromatin?

• A. Euchromatin is found only in prokaryotes, whereas heterochromatin is exclusive to eukaryotes.
• B. Heterochromatin contains most of the actively transcribed genes, while euchromatin is mostly silent.
• C. Both euchromatin and heterochromatin are equally accessible to RNA polymerase during transcription.
• D. Euchromatin is less condensed and generally transcriptionally active, while heterochromatin is more condensed and typically transcriptionally inactive.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the definitions of euchromatin and heterochromatin. Euchromatin is a form of chromatin that is less condensed and generally associated with active transcription, meaning genes in these regions are often expressed.
2. Step 2: Recognize that heterochromatin is more condensed chromatin, which is typically transcriptionally inactive or silent, meaning genes in these regions are usually not expressed.
3. Step 3: Evaluate the statements given by comparing them to these definitions. For example, check if euchromatin is exclusive to prokaryotes (it is not, as prokaryotes do not have chromatin structured like eukaryotes).
4. Step 4: Consider the accessibility of chromatin to RNA polymerase. Euchromatin is more accessible, allowing transcription machinery to bind, whereas heterochromatin is less accessible due to its condensed state.
5. Step 5: Conclude that the correct distinguishing statement is that euchromatin is less condensed and generally transcriptionally active, while heterochromatin is more condensed and typically transcriptionally inactive.