Which of the Following is True Regarding Heterochromatin in a Typical

Question

Which of the following is true regarding heterochromatin in a typical mammalian cell?
A) About 1% of the nuclear genome is packaged in heterochromatin.
B) The DNA in heterochromatin contains all of the inactive genes in a cell.
C) Genes that are packaged in heterochromatin are permanently turned off.
D) The different types of heterochromatin share an especially high degree of compaction.
E) Heterochromatin is highly concentrated in the centromeres but not the telomeres.

Accepted Answer

Heterochromatin covers a significant fraction of the mammalian genome including the centromere and telomere neighborhoods, but contains very few, mostly inactive, genes. Even though heterochromatin has a very high degree of compaction, its genes can still become active under appropriate conditions through the remodeling of the chromatin into more open arrangements. There are many genes that are not packaged in heterochromatin but are nevertheless transcriptionally inactive.