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Tsix
Tsix is a non-coding RNA gene that is antisense to the Xist RNA. Tsix binds Xist during X chromosome inactivation. The name Tsix comes from the reverse of Xist, which stands for X-inactive specific transcript. Background Female mammals have two X chromosomes and males have one X and one Y chromosome. The X chromosome has many active genes. This leads to dosage compensation problems: the two X chromosomes in the female will create twice as many gene products as the one X in the male. To mitigate this, one of the X chromosomes is inactivated in females, so that each sex only has one set of X chromosome genes. The inactive X chromosome in cells of females is visible as a Barr body under the microscope. Males do not have Barr bodies, as they only have one X chromosome. Xist is only expressed from the future inactive X chromosome in females and is able to "coat" the chromosome from which it was produced. Many copies of Xist RNA bind the future inactivated X chromosome. Tsix pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tsix Flowchart
Tsix is a non-coding RNA gene that is antisense to the Xist RNA. Tsix binds Xist during X chromosome inactivation. The name Tsix comes from the reverse of Xist, which stands for X-inactive specific transcript. Background Female mammals have two X chromosomes and males have one X and one Y chromosome. The X chromosome has many active genes. This leads to dosage compensation problems: the two X chromosomes in the female will create twice as many gene products as the one X in the male. To mitigate this, one of the X chromosomes is inactivated in females, so that each sex only has one set of X chromosome genes. The inactive X chromosome in cells of females is visible as a Barr body under the microscope. Males do not have Barr bodies, as they only have one X chromosome. Xist is only expressed from the future inactive X chromosome in females and is able to "coat" the chromosome from which it was produced. Many copies of Xist RNA bind the future inactivated X chromosome. Tsix preve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-inactivation
X-inactivation (also called Lyonization, after English geneticist Mary Lyon) is a process by which one of the copies of the X chromosome is inactivated in therian female mammals. The inactive X chromosome is silenced by being packaged into a transcriptionally inactive structure called heterochromatin. As nearly all female mammals have two X chromosomes, X-inactivation prevents them from having twice as many X chromosome gene products as males, who only possess a single copy of the X chromosome (see dosage compensation). The choice of which X chromosome will be inactivated in a particular embryonic cell is random in placental mammals such as humans, but once an X chromosome is inactivated it will remain inactive throughout the lifetime of the cell and its descendants in the organism (its cell line). The result is that the choice of inactivated X chromosome in all the cells of the organism is a random distribution, often with about half the cells having the paternal X chrom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dosage Compensation
Dosage compensation is the process by which organisms equalize the expression of genes between members of different biological sexes. Across species, different sexes are often characterized by different types and numbers of sex chromosomes. In order to neutralize the large difference in gene dosage produced by differing numbers of sex chromosomes among the sexes, various evolutionary branches have acquired various methods to equalize gene expression among the sexes. Because sex chromosomes contain different numbers of genes, different species of organisms have developed different mechanisms to cope with this inequality. Replicating the actual ''gene'' is impossible; thus organisms instead equalize the ''expression'' from each gene. For example, in humans, female (XX) cells randomly silence the transcription of one X chromosome, and transcribe all information from the other, expressed X chromosome. Thus, human females have the same number of expressed X-linked genes per cell as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-chromosome Reactivation
X chromosome reactivation (XCR) is the process by which the inactive X chromosome (the Xi) is re-activated in the cells of eutherian female mammals. Therian female mammalian cells have two X chromosomes, while males have only one, requiring X-chromosome inactivation (XCI) for sex-chromosome dosage compensation. In eutherians, XCI is the random inactivation of one of the X chromosomes, silencing its expression. Much of the scientific knowledge currently known about XCR comes from research limited to mouse models or stem cells. Partial XCR may derepress one or more genes on the Xi, and the level of restored gene expression may not be as high as it would normally be on the active X chromosome (the Xa). Complete XCR restores the Xi to Xa and erases the epigenetic memory of XCI, meaning that inducing X-inactivation again will randomly select an X chromosome to silence, rather than deterministically silencing the original Xi. XCR is an emerging topic of interest for multiple reasons: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Barr Body
A Barr body (named after discoverer Murray Barr) or X-chromatin is an inactive X chromosome. In species with XY sex-determination (including humans), females typically have two X chromosomes, and one is rendered inactive in a process called lyonization. Errors in chromosome separation can also result in male and female individuals with extra X chromosomes. The Lyon hypothesis states that in cells with multiple X chromosomes, all but one are inactivated early in embryonic development in mammals.Brown, C.J., Robinson, W.P., (1997), XIST Expression and X-Chromosome Inactivation in Human Preimplantation Embryos ''Am. J. Hum. Genet.'' 61, 5–8Full Text PDF The X chromosomes that become inactivated are chosen randomly, except in marsupials and in some extra-embryonic tissues of some placental mammals, in which the X chromosome from the sperm is always deactivated. In humans with euploidy, a genotypical female (46, XX karyotype) has one Barr body per somatic cell nucleus, w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-coding RNA
A non-coding RNA (ncRNA) is a functional RNA molecule that is not Translation (genetics), translated into a protein. The DNA sequence from which a functional non-coding RNA is transcribed is often called an RNA gene. Abundant and functionally important list of RNAs, types of non-coding RNAs include transfer RNAs (tRNAs) and ribosomal RNAs (rRNAs), as well as small RNAs such as microRNAs, siRNAs, piRNAs, snoRNAs, snRNAs, Extracellular RNA, exRNAs, scaRNAs and the long noncoding RNA, long ncRNAs such as Xist and HOTAIR. The number of non-coding RNAs within the human genome is unknown; however, recent Transcriptomics, transcriptomic and Bioinformatics, bioinformatic studies suggest that there are thousands of non-coding transcripts. Many of the newly identified ncRNAs have unknown functions, if any. There is no consensus on how much of non-coding transcription is functional: some believe most ncRNAs to be non-functional "junk RNA", spurious transcriptions, while others expect that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Imprinting
Genomic imprinting is an epigenetic phenomenon that causes genes to be expressed or not, depending on whether they are inherited from the female or male parent. Genes can also be partially imprinted. Partial imprinting occurs when alleles from both parents are differently expressed rather than complete expression and complete suppression of one parent's allele. Forms of genomic imprinting have been demonstrated in fungi, plants and animals. In 2014, there were about 150 imprinted genes known in mice and about half that in humans. As of 2019, 260 imprinted genes have been reported in mice and 228 in humans. Genomic imprinting is an inheritance process independent of the classical Mendelian inheritance. It is an epigenetic process that involves DNA methylation and histone methylation without altering the genetic sequence. These epigenetic marks are established ("imprinted") in the germline (sperm or egg cells) of the parents and are maintained through mitotic cell divisions in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
