Mathematical modeling shows why animals see at night

Nocturnal and diurnal mammals see the same—but only for a brief time. When mice are born, the chromatin in the cells of their eyes has a diurnal structure. Day by day, the layout of this chromatin slowly inverts, allowing ...

What organizes the genome in the nucleus?

Spatial separation of active from inactive fractions of the genome in the cell nucleus is crucial for gene expression control. A new study uncovers leading mechanisms of such separation and turns our picture of the nucleus ...

Keeping chromosomes in check: A new role for heterochromatin

Although many people are aware that chromosomal damage and shortening contribute to the aging process, understanding how chromosomal defects occur is about more than just finding a way to turn back the clock. Large changes ...

The nanoscopic structure that locks up our genes

For decades, scientists could only speculate about the shape of heterochromatin, a type of chromatin that consists of tightly packed DNA and proteins. Recently, however, researchers from the Okinawa Institute of Science and ...

Histone 1, the guardian of genome stability

Scientists headed by Ferran Azorín at the Institute for Research in Biomedicine (IRB Barcelona) have discovered why histone 1 is a major protection factor against genomic instability and a vital protein. Their study of the ...

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Heterochromatin

Heterochromatin is a tightly packed form of DNA, which comes in different varieties. These varieties lie on a continuum between the two extremes of constitutive and facultative heterochromatin. Both play a role in the expression of genes, where constitutive heterochromatin can affect the genes near them (position-effect variegation) and where facultative heterochromatin is the result of genes that are silenced through a mechanism such as histone methylation or siRNA through RNAi. Constitutive heterochromatin is usually repetitive and forms structural functions such as centromeres or telomeres, in addition to acting as an attractor for other gene-expression or repression signals. Facultative heterochromatin is not repetitive and although it shares the compact structure of constitutive heterochromatin, facultative heterochromatin can, under specific developmental or environmental signaling cues, lose its condensed structure and become transcriptionally active. Heterochromatin is often associated with the di and tri-methylation of H3K9.

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