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Independent protein aggregates that cause epigenetic effects are called ‘prions’. Prions are an unusual form of epigenetics. Their stable inheritance and complex phenotypes come about through protein folding rather than nucleic acid-associated changes. They are linked to chromosomal remodelling factors. Swil, a subunit of SWI/SNF chromatin remodelling complex and this protein can become a prion. […]
Epigenetic inheritance describes the ability of different states, which may have different phenotypic consequences to be inherited without any change in the sequence of the DNA (Figure 10.3). Epigenetic mechanisms can be divided into two classes. Figure 10.3 (a) Types of epigenetic information (b) Inheritance of DNA methylation in somatic cells Methylation establishes the […]
The pattern of methylation of germ cells is established in each sex during gametogenesis. This takes place in two steps. In males, the methylation pattern develops in two stages: first, the methylation pattern that is characteristic of mature sperm is established in the spermatocyte. Further changes in the pattern are made during fertilization. In females, […]
DNA methylation occurs at specific sites. In bacteria, the DNA methylation is used for identifying bacterial restriction-methylation system that is involved in phage defence and is also used for distinguishing replicated and non-replicated DNA. In eukaryotes, the DNA methylation is connected with the control of transcription. The methylation of a control region is usually accompanied […]
Polycomb group (PcG) proteins perpetuate a state of repression of genes through cell division. The polycomb responsive element (PRE) is a DNA sequence that is required for the action of PcG. The PRE provides a nucleation centre from which PcG proteins propagate an inactive structure. The trithorax group (trxG) proteins antagonize the action of PcG. […]
Euchromatin and heterochromatin can be localized during the interphase in the nucleus. Heterochromatin is highly inert and condensed, transcriptionally repressed, replicates during the late S-phase and is found in the periphery of the nucleus. Centromeric heterochromatin predominantly consists of satellite DNAs. When a gene is transferred to a position adjacent to the heterochromatin, it may […]
Epigenetics is the study of heritable changes in gene expression or cellular phenotype that is caused by mechanisms that do not involve changes in DNA sequence. In practice, epigenetics is the study of gene expression or phenotype changes. The Greek word ‘epi’ means over, above or outer and the word genetics means study of genes. […]