Publish Your Research Online
Get Recognition - International Audience
Request for an Author Account | Login | Submit Article
|HOME||FAQ||TOP AUTHORS||FORUMS||PUBLISH ARTICLE|
Dosage Compensation: How Male Equals Female in Gene ExpressionBY: Chandra Kala | Category: Biology | Submitted: 2012-10-25 12:03:26
Article Summary: "X-chromosomal inactivation or Dosage compensation is the wonderful mechanism developed in nature to unify the level of gene expressions in both sexes. Coat color of mammals is classical example of X chromosome inactivation. The advanced research in X-chromosome inactivation can solve the problems associated with X-linked diseas.."
The male and females of a species are distinct and each will have its one genetic content. The numbers of autosomes in both organisms are same in diploid conditions and there is no mechanism to change level of expression of gene products on autosomes. The situation is not the same in case of Allosomes or X-chromosomes, the males and females will have different numbers sex chromosomes either as XY or XX, ZZ or ZW, etc. The Y chromosome contains high heterochromatin content and has only few genes, while X-chromosome contains hundreds of genes, some of which are very essential for the survival of the organisms. X-chromosome contains genes that are required for brain function and sexual reproduction. Females have two X-chromosomes and hence have double the content of genetic material with respect to X-chromosome by comparing with males which have only one X-chromosomes. Reading on the genetic content, the females should express double the gene products of the genes that are present in the X-chromosome. This might have lead to favoring of one particular sex in nature. To tackle this phenomenon, nature has developed a fabulous phenomenon called Dosage Compensation. Dosage Compensation is the mechanism of equalizing the amount of expressible genetic content in both sexes.
Mary Lyon to explain the fur coat color of mice hypothesized random inactivation of X-chromosomes in female. Further Murray Barr identified highly condensed heterochromatin in the somatic cells of female called Barr body. Barr bodies are localized in the periphery of the resting somatic cells. In heterozygous organism, except for one X-chromosome, all additional X-chromosomes becomes inactive and forms a highly condensed Heterchromatin in the somatic phase. In gametic cells or germ cells, there is no X-chromosome inactivation or Lyonization. Hence Lyonization mechanism is observed only in somatic cells. The Barr body is utilized in detecting number of X-chromosomes present in individuals during the initial level of screening for chromosomal variations. Normal females will have two X-chromosomes and has one Barr body and the number of Barr bodies increases with the increase in the number of X-chromosomes, which can be detected using buccal smear technique.
The pattern of Inactivation of X-chromosome differs from organisms to organisms. In some organism like humans, the pattern of X-inactivation is highly random, mosaic pattern is observed in the expression of genes that are coming from paternal/ father side and maternal / mother side. Coat color of mammals is classical example of X-chromosome inactivation where in few somatic cells X-chromosome from father is inactivated, while in other somatic cells, the X-chromosome from mother is inactivated. Though the procedure for selection of X-chromosome for inactivation is random, but the process once occurred is irreversible in somatic cells. The cells having inactivated paternal X-chromosome will always have the functional maternal X-chromosome and vice versa throughout the life cycle of the organism.
In mammals, the inactivation of X-chromosome is regulated by Xic loci (X-inactivation centre). Xic codes for a non protein coding RNA of 19Kb called Xist. Xist RNA binds to the same X-chromosome that expresses it in cis and triggers X-chromosome inactivation. The chromatin of the X-chromosome after Xist RNA coating/binding changes into tight heterochromatin. Histone methylation and acetylation modifications are observed after Xist binding to X-chromosome and play a critical role in X-chromosome inactivation. Further the inactivated X-chromosome replicates asynchronously in somatic cells compared to the active X-chromosome homologue during cell replication. To explain the mechanism of X-inactivation many theories have been proposed and to date it is very difficult to explain the complete mechanism of X-inactivation and selection of X-chromosome for inactivation.
X chromosomal inactivation is the wonderful mechanism developed in nature to unify the level of gene expressions in both sexes. The research on X-chromosomal inactivation has many applications on human health. Due to X-chromosome inactivation, alleles which are recessive get expressed because of suppression of dominant gene in heterozygous conditions. The reactivation suppressed dominant/wild type gene because of X-inactivation can cure the diseases like muscular dystrophy, fragile X-syndrome, etc., that are X-linked in females.
About Author / Additional Info:
An enthuiastic author from India
Comments on this article: (0 comments so far)
• Experimental Animal Models of Rheumatoid Arthritis
• Stomata and Water Cycle
• New Dimension of Scope and Career in Microbiology
• Carotenoids- Introduction, Origin and Properties
Latest Articles in "Biology" category:
• Wonderful World of Microorganisms and Their Role in Human Life.
• Molecular Biology Techniques
• Process of Reproduction in Bacteria
• Importance of Microorganisms in the Ecosystem
• Starting From the Basics: DNA Extraction
• Agrobacetium-Mediated Transformation Protocol
• Sucrose Regulating Photosynthesis
• Nitrogen Fixation: Genes Involved and the Infection Process
• Functional Genomics: A Tool in Genetic Engineering
• Plant Tissue Culture and Its Applications
• Harmful Effects of Mold and Their Prevention
• Gel Electrophoresis in Molecular Biology
• Extraction of Phytochemicals
• Applications of Thin Layer Chromatography
• Beneficial and Harmful Bacteria
• Calvin Cycle Regulation and Effect on Photosynthesis
• How a Baby Develops Inside Mother's Womb: From an Embryo to a Child
• Apoptosis (or cell suicide) : Process and Types
• Neurotransmitters and its types
Important Disclaimer: All articles on this website are for general information only and is not a professional or experts advice. We do not own any responsibility for correctness or authenticity of the information presented in this article, or any loss or injury resulting from it. We do not endorse these articles, we are neither affiliated with the authors of these articles nor responsible for their content. Please see our disclaimer section for complete terms.
Copyright © 2010 biotecharticles.com - Do not copy articles from this website.
ARTICLE CATEGORIES :
| Disclaimer/Privacy/TOS | Submission Guidelines | Contact Us