BIO130H1 Chapter Notes - Chapter 12.4: Genetic Recombination, Centromere, Meiosis
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BIO130H1 Full Course Notes
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12. 4: heterochromatin: after mitosis has been completed, most of the chromatin in highly compacted mitotic chromosomes returns to its diffuse interphase condition. Heterochromatin: they have little transcriptional activity, divided into two classes, constitutive. Remains in the compacted state in all cells at all times. Found in regions that 469 flank the telomeres and centromere of each chromosome and in a few other sites, such as the distal arm of the y chromosome in male mammals. Consists primarily of repeated sequences and contains relatively few genes. When genes that are normally active move into a position adjacent to these regions (as a result of transposition or translocation) tend to become transcriptionally silenced. The spread of heterochromatin along the chromosome is apparently blocked by specialized barrier sequences (boundary elements) in the genome. Serves to inhibit genetic recombination between homologous repetitive sequences: facultative.
