Inactivation of whole chromosomes in mammals and coccids: some comparisons

Hs, Chandra

doi:10.1017/s0016672300012672

Cited by 11 publications

(6 citation statements)

References 53 publications

(32 reference statements)

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“…Together, these observations indicate that the paternal set changes from an inactive to an active state 'and that this occurs as a normal developmental process. Chandra (61) considers that such changes may pe a basic property of facultative heterochromatin. .…”

Section: Subsequent Changes In Activitymentioning

confidence: 99%

Control of Chromosome Inactivation

Cattanach

1975

Annu. Rev. Genet.

135

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Section: Subsequent Changes In Activitymentioning

confidence: 99%

Control of Chromosome Inactivation

Cattanach

1975

Annu. Rev. Genet.

135

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“…Since constitutive heterochromatin is rich in repetitious DNA it may well have different control mechanisms from those of facultative heterochromatin, of which the most useful example, apart from the mammalian X-chromosome, is found in mealy bugs. Here, in male embryos the entire paternally derived haploid set of chromosomes becomes heterochromatic and inactive early in development, whereas in female embryos both sets remain euchromatic (Brown, 1966; Chandra, 1971). Comparisons of mammalian X-chromosomes with mealy bug chromosomes may be valuable.…”

Section: Mechanism Of X-chromosome Inactivationmentioning

confidence: 99%

X‐chromosome Inactivation and Developmental Patterns in Mammals

1972

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Summary 1. The review considers information from mammalian embryology relevant to X‐chromosome inactivation, and from X‐inactivation relevant to mammalian embryology. 2. Properties of the inactive‐X, by which it may be recognized are: sex chromatin, heteropycnosis, late replication and the absence of gene product. Each of these has advantages and disadvantages in particular circumstances. In some species the X carries constitutive heterochromatin, which must be distinguished from the facultative region. 3. The time of X‐chromosome inactivation can be estimated from the time of appearance of sex chromatin or late replication, or inferred from the appearance of heterozygotes for X‐linked genes or of experimental chimaeras. The estimated time varies with species, and in the mouse and rabbit is near the time of increase in RNA synthesis. 4. Whereas in eutherian mammals either the maternally or the paternally derived X may be inactivated in different cell lines, in marsupials the paternal X is always the inactive one. 5. During development various factors act to distort the patterns produced by random X‐inactivation. These factors include cell selection, transfer of gene product, and migration and mingling of cells. 6. There is no clear evidence that X‐chromosome inactivation is not complete. 7. In female germ cells both X‐chromosomes appear to be active. In male ones both X and Y appear inactive during most of spermatogenesis, although probably in early stages all X chromosomes present are active. 8. The active and inactive X‐chromosomes may be differentiated by presence or absence of some non‐histone protein or other polyanionic substance. 9. If the genes concerned in synthesis or attachment of this substance are on the X‐chromosome then the differentiation will be self‐maintaining. 10. The initiation of the differentiation requires either the attachment of different X‐chromosomes to different sites, or some interaction of X‐linked and autosomal genes, concerned in inducing or repressing activity. Some possible models are discussed.

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“…The phenomenon of X inactivation evolved fairly recently, at about the time of emergence of the common precursor of mammals and marsupials (Ohno, 1969). A mechanism for the inactivation of entire chro mosomes has also evolved in some insects, e.g., mealy bugs (Brown and N ur, 1964;C handra, 1971). Ohno (1969Ohno ( , 1973 argues that since evolution is a very conservative process, seldom using truly new mechanisms, X in activation probably results from minor variations of the basic mechanisms of gene regulation and differentiation.…”

mentioning

confidence: 99%

X inactivation, differentiation, and DNA methylation

Riggs

1975

Cytogenet Genome Res

1,186

609

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A model based on DNA methylation is proposed to explain the initiation and maintenance of mammalian X inactivation and certain aspects of other permanent events in eukaryotic cell differentiation. A key feature of the model is the proposal of sequence-specific DNA methylases that methylate unmethylated sites with great difficulty but easily methylate half-methylated sites. Although such enzymes have not yet been detected in eukaryotes, they are known in bacteria. An argument is presented, based on recent data on DNA-binding proteins, that DNA methylation should affect the binding of regulatory proteins. In support of the model, short reviews are included covering both mammalian X inactivation and bacterial restriction and modification enzymes.

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Inactivation of whole chromosomes in mammals and coccids: some comparisons

Cited by 11 publications

References 53 publications

Control of Chromosome Inactivation

Control of Chromosome Inactivation

X‐chromosome Inactivation and Developmental Patterns in Mammals

X inactivation, differentiation, and DNA methylation

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