Which type of chromatin is less tightly packed and typically accessible for transcription?

Euchromatin is less tightly packed and generally more accessible for transcription because it is a form of chromatin that is associated with actively expressed genes. This structure allows transcription machinery, such as RNA polymerase and transcription factors, to access the DNA more easily. The less compact arrangement of euchromatin means that the DNA is in a conformation that is conducive to the unwinding necessary for the transcription process.

In contrast, heterochromatin represents a more condensed form of chromatin that is typically transcriptionally inactive. It is found in regions of the genome that do not express genes frequently and often plays a role in maintaining structural integrity and regulating the access of proteins to the DNA.

Interchromatin is not a standard classification of chromatin but might refer to the spaces between areas of chromatin. Pericentric heterochromatin refers specifically to heterochromatin located near the centromeres of chromosomes and is also largely inactive in terms of transcription.

Overall, the characteristics of euchromatin as being less compact and more transcriptionally active underscore why it is the correct answer in this context.