Is it true that under some conditions, Facultative Heterochromatin can become Euchromatin which is potentially transcribed?
The Lewin definition of facultative heterochromatin is “the inert state of sequences that also exist in active copies.” The basic idea is that some sequences/chromosomes are packaged (e.g. X chromosomes in females) as both heterochromatin and euchromatin (although not simultaneously or reversibly). Heterochromatin is an essentially permanent state. Euchromatin can undergo varying degrees of condensation such that actively transcribed genes are losely packaged while genes that are inducible but which are not actively transcribed are more densely packed. In answer to your direct question, no, facultative heterochromatin cannot be reversibly unpackaged, converted to euchromatin and transcribed. p.s. This is almost completely true. As it turns out, however, in certain tissues (e.g. microvilli in the intestine) the inactive X is reactivated; and certain genes on the inactive X in all tissues (e.g. XIST) are transcribed. How do you like that waffling?
Related Questions
- In 5.3, there are conditions that require a new or partial FAI when a change occurs "that can potentially affect fit, form or function". How is this assessed?
- Is it true that under some conditions, Facultative Heterochromatin can become Euchromatin which is potentially transcribed?
- What is the difference between euchromatin and heterochromatin?
