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Dosage compensation
About: Dosage compensation is a research topic. Over the lifetime, 1920 publications have been published within this topic receiving 124589 citations.
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TL;DR: The data demonstrate that there is no overall silencing of the additional two sets of autosomes in the tetraploid cells, but the X chromosomes could be subject to an irregular dosage compensation.
15 citations
TL;DR: In this paper, the authors examined thymidine labeling patterns in gynandric mosaic salivary glands of drosophila melanogaster and found that the X chromosome of the XO2A cells always had fewer sites labeled than the X chromosomes of the XX2A nuclei, for a given pattern of the autosomes in either sex.
Abstract: [(3)H]Thymidine labeling patterns have been examined in gynandric mosaic salivary glands of drosophila melanogaster. The Ring-X stock, R(1) w(ve)/In(1)dl 49, l (1) J1 y w lz(s), was used for this purpose. 365 labeled XX2A and 40 labeled XO2A nuclei were obtained from a total of 624 nuclei in nine pairs of mosaic salivary glands. It was observed that in all but those nuclei which had DD, 1C, and 2C patterns, the X chromosome of the XO2A nuclei always had fewer sites labeled than the X chromosomes of the XX2A nuclei, for a given pattern of the autosomes in either sex. Such asynchronous labeling of the X chromosome in the XO2A (male) nuclei was observed regardless of the proportion of the XO2A cells (2.0-73.7 percent), in the mosaic glands. Moreover, while the frequency of [(3)H]thymidine labeling for all of the 39 replicating units except the two late replicating sites (3C and 11A) in the X chromosome of the XO2A nuclei, was consistently lower than in the X chromosome of the XX2A nuclei, the mean number of grains on the X chromosome was relatively (to autosomes) similar in both XX2A and XO2A cells. The results, therefore, suggest that, as in XY2A larval glands, the X chromosome in the XO2A cells also completes the replication earlier than autosomes and that the XO2A nuclei show cellular autonomy with respect to the early replication of the X chromosome, like its counterpart, RNA transcription. Absence of the asynchrony during the initial phase (DD-2C) further completes the replication earlier but that the rate of replication of its DNA is possibly faster, and (b) that there might be a common regulation with respect to the initiation of replication of different chromosomes in a genome.
15 citations
TL;DR: Choosing between these alternatives is important for understanding a number of features of X-chromosome differentiation, including the derivation of molecular and genetic models of this process and the determination of the timing of this differentiation.
Abstract: It is widely accepted that only one of two X chromosomes present in the somatic cells of female mammals is active (Lyon 1961). This results in a similar dosage relationship between functional X chromosomes and autosomes in females and males. This compensation occurs early in development between the 2-cell stage (Hoppe and Whitten 1972) and the time of implantation of the embryo into the uterus (Gardner and Lyon 1971). An important issue concerning X-chromosome differentiation is the functional state of X chromosomes during early embryogenesis, before irreversible dosage compensation occurs. That is, does X-chromosome differentiation involve a process of X-chromosome inactivation or X-chromosome activation? Choosing between these alternatives is important for understanding a number of features of X-chromosome differentiation, including:
(1)
the derivation of molecular and genetic models of this process, and
(2)
the determination of the timing of this differentiation.
15 citations
TL;DR: Recent molecular genetic and biochemical studies have provided new insights into how regulatory factors in Drosophila are recruited and assembled on the X chromosome, leading to the essential hypertranscription of its genes.
Abstract: From worms to humans, recognizing and modifying a specific chromosome is essential for dosage compensation, the mechanism by which equal X-linked gene expression in males and females is achieved. Recent molecular genetic and biochemical studies have provided new insights into how regulatory factors in Drosophila are recruited and assembled on the X chromosome, leading to the essential hypertranscription of its genes.
15 citations
TL;DR: A phenotypically normal female, carrier of an apparently balanced X;14 translocation t(X;14)(q22;q24.3) in all her cells and a small interstitial deletion of band 15q112 in some of her cells had 2 offspring and represents a fifth case of balanced X-autosome translocation with the break point inside the postulated critical region of Xq(q13 q26) associated with fertility.
Abstract: We report on a family in which an X;14 translocation has been identified. A phenotypically normal female, carrier of an apparently balanced X-autosome translocation t(X;14)(q22;q24.3) in all her cells and a small interstitial deletion of band 15q112 in some of her cells had 2 offspring. She represents a fifth case of balanced X-autosome translocation with the break point inside the postulated critical region of Xq(q13 q26) associated with fertility. The break point in this case is located in Xq22, the same band as in four previously published exceptional cases. In most of her cells, the normal X was inactivated. Her daughter, the proposita, has an unbalanced karyotype 46,X,der(X), t(X;14)(q22;q24.3)mat, del(15)(q11.1q11.3)mat. She is mildly retarded and has some Prader-Willi syndrome manifestations. She has two normal 14 chromosomes, der(X), and deletion 15q11.2. Her clinical abnormalities probably could be attributed to the deletions 15q and Xq rather than 14q duplication. In most of cells, der(X) was inactivated. We assume that spreading of inactivation was extended to the 14q segment on the derivative X. Late replication and gene dose studies support this view. Another daughter, who inherited the balanced X;14 translocation and not deletion 15 chromosome, is phenotypically normal.
15 citations