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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 preven ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tsix Flowchart
Tsix is a non-coding RNA gene that is antisense to the XIST (gene), 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. ... [...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 chromos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X Chromosome 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 chromosom ... [...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, females (XX) silence the transcription of one X chromosome of each pair, and transcribe all information from the other, expressed X chromosome. Thus, human females have the same number of expressed X-linked genes as do human males ( ... [...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 a cell with more than one X chromosome, rendered inactive in a process called lyonization, in species with XY sex-determination (including humans). The Lyon hypothesis states that in cells with multiple X chromosomes, all but one are inactivated during mammalian embryogenesis. This happens early in embryonic development at random 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 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, while a genotypical male (46, XY) has none. The Barr body can be seen in the interphase nucleus as a darkly staining small mass in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-coding RNA
A non-coding RNA (ncRNA) is a functional RNA molecule that is not 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 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, exRNAs, scaRNAs and the long ncRNAs such as Xist and HOTAIR. The number of non-coding RNAs within the human genome is unknown; however, recent transcriptomic and bioinformatic studies suggest that there are thousands of non-coding transcripts. Many of the newly identified ncRNAs have not been validated for their function. There is no consensus in the literature on how much of non-coding transcription is functional. Some researchers have argued that many ncRNAs are non-functional (sometimes referred to as "junk RNA"), spurious transcriptions. Others, however, disagree, arguing instead that many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homozygous
Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Most eukaryotes have two matching sets of chromosomes; that is, they are diploid. Diploid organisms have the same loci on each of their two sets of homologous chromosomes except that the sequences at these loci may differ between the two chromosomes in a matching pair and that a few chromosomes may be mismatched as part of a chromosomal sex-determination system. If both alleles of a diploid organism are the same, the organism is homozygous at that locus. If they are different, the organism is heterozygous at that locus. If one allele is missing, it is hemizygous, and, if both alleles are missing, it is nullizygous. The DNA sequence of a gene often varies from one individual to another. These gene variants are called alleles. While some gen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cellular Differentiation
Cellular differentiation is the process in which a stem cell alters from one type to a differentiated one. Usually, the cell changes to a more specialized type. Differentiation happens multiple times during the development of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types. Differentiation continues in adulthood as adult stem cells divide and create fully differentiated daughter cells during tissue repair and during normal cell turnover. Some differentiation occurs in response to antigen exposure. Differentiation dramatically changes a cell's size, shape, membrane potential, metabolic activity, and responsiveness to signals. These changes are largely due to highly controlled modifications in gene expression and are the study of epigenetics. With a few exceptions, cellular differentiation almost never involves a change in the DNA sequence itself. Although metabolic composition does get altered quite dramaticall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autosome
An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosome, allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosomes is collectively known as atDNA or auDNA. For example, humans have a diploid human genome, genome that usually contains 22 pairs of autosomes and one allosome pair (46 chromosomes total). The autosome pairs are labeled with numbers (1–22 in humans) roughly in order of their sizes in base pairs, while allosomes are labelled with their letters. By contrast, the allosome pair consists of two X chromosomes in females or one X and one Y chromosome in males. Unusual combinations of XYY syndrome, XYY, Klinefelter syndrome, XXY, Triple X syndrome, XXX, XXXX syndrome, XXXX, XXXXX syndrome, XXXXX or XXYY syndrome, XXYY, among Aneuploidy, other Salome combinations, are known to occur and usually cause developmental abnormalities. Autosomes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CpG Island
The CpG sites or CG sites are regions of DNA where a cytosine nucleotide is followed by a guanine nucleotide in the linear sequence of bases along its 5' → 3' direction. CpG sites occur with high frequency in genomic regions called CpG islands (or CG islands). Cytosines in CpG dinucleotides can be methylated to form 5-methylcytosines. Enzymes that add a methyl group are called DNA methyltransferases. In mammals, 70% to 80% of CpG cytosines are methylated. Methylating the cytosine within a gene can change its expression, a mechanism that is part of a larger field of science studying gene regulation that is called epigenetics. Methylated cytosines often mutate to thymines. In humans, about 70% of promoters located near the transcription start site of a gene (proximal promoters) contain a CpG island. CpG characteristics Definition ''CpG'' is shorthand for ''5'—C—phosphate—G—3' '', that is, cytosine and guanine separated by only one phosphate group; phosphate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pluripotency
Pluripotency: These are the cells that can generate into any of the three Germ layers which imply Endodermal, Mesodermal, and Ectodermal cells except tissues like the placenta. According to Latin terms, Pluripotentia means the ability for many things. We can generate Induced Pluripotent cells by using the Induced pluripotency technique by triggering or expressing the genes or the transcription factors of the normal somatic cells. They are abbreviated as iPSC or IPS. We can forcefully express the transcription factors like Oct4, Sox2, Klf4, and c-Myc of a non-pluripotent cell and convert them into a stem cell. This procedure is first studied in a Mouse fibroblast cell in 2006 and followed the same instructions in developing a Human pluripotent cell from a Human epidermal fibroblast cell. The technique is called Regeneration. Though the iPSC has similar properties to embryonic stem cells they were never approved for clinical stage research because they are highly Tumerogenic, hav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rex1
Rex1 (Zfp-42) is a known marker of pluripotency, and is usually found in undifferentiated embryonic stem cells. In addition to being a marker for pluripotency, its regulation is also critical in maintaining a pluripotent state. As the cells begin to differentiate, Rex1 is severely and abruptly downregulated. Discovery Rex1 was discovered by Hosler, BA et al. in 1989 when studying F9 murine teratocarcinoma stem cells. They found that these teratocarcinoma stem cells expressed high levels of Rex1, and that they resembled pluripotent stem cells of the inner cell mass (ICM). Hosler, BA et al. found that these teratocarcinoma stem cells, when in the presence of retinoic acid (RA), differentiated into nontumorigenic cells resembling extraembryonic endoderm of early mouse embryos. They were able to isolate the nucleotide sequence for Rex1 using differential hybridization of an F9 cell. They named it Rex1 for reduced expression 1 because there was a steady decline of its mRNA levels wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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