Translation and Protein Localization
Very sophisticated and complex stories about the production of protein. Long long way. :(
среда, 2 апреля 2008 г.
среда, 19 марта 2008 г.
вторник, 18 марта 2008 г.
Epigenetic
Epigenetics is a term in biology used today to refer to features such as chromatin and DNA modifications that are stable over rounds of cell division but do not involve changes in the underlying DNA sequence of the organism.[1] These epigenetic changes play a role in the process of cellular differentiation, allowing cells to stably maintain different characteristics despite containing the same genomic material. Epigenetic features are inherited when cells divide despite a lack of change in the DNA sequence itself and, although most of these features are considered dynamic over the course of development in multicellular organisms, some epigenetic features show transgenerational inheritance and are inherited from one generation to the next.[2]
Specific epigenetic processes include paramutation, bookmarking, imprinting, gene silencing, X chromosome inactivation, position effect, reprogramming, transvection, maternal effects, the progress of carcinogenesis, many effects of teratogens, regulation of histone modifications and heterochromatin, and technical limitations affecting parthenogenesis and cloning.
Nuclear Hormone Receptors
Ligand Binding Domain The LBD participates in several activities including hormone binding, homo- and/or heterodimerization, formation of the heat-shock protein complex and transcriptional activation and repression. The binding of the hormone induces conformational changes that seem to control these properties and influence gene expression. The conformational changes that accompany the transition between the liganded and unliganded forms of the nuclear hormone receptors affect dramatically their affinity for other proteins. In order to understand the functional role of the hormone one must understand the binding mechanism by which the hormone induces conformational changes.
Nuclear Hormone Receptor
DNA binding domainThe central DBD is responsible for targeting the receptors to their hormone response elements (HRE). The DNA binding domain, classified as a type-II zinc finger motif, has two subdomains, each containing a zinc ion coordinated by four cysteine residues, followed by an alpha-helix. The DBD binds as a dimer with each monomer recognizing a six base pair sequence of DNA. The reading helix of each monomer makes sequence specific contacts in the major groove of the DNA at each half-site. These contacts allow the dimer to read the sequence, spacing and orientation of the half-sites within its response element, and thus discriminate between sequences. These proteins exhibit, however, a flexibility in recognizing DNA sequences and also accept a variety of amino-acid substitutions in their reading helix without abolishing binding.
Heat shock proteins (HSP)
Heat shock proteins (HSP) are a group of proteins whose expression is increased when the cells are exposed to elevated temperatures or other stress. This increase in expression is transcriptionally regulated. This dramatic upregulation of the heat shock proteins induced mostly by Heat Shock Factor (HSF) is a key part of the heat shock response.
chaperones
In molecular biology, chaperones are proteins that assist the non-covalent folding/unfolding and the assembly/disassembly of other macromolecular structures, but do not occur in these structures when the latter are performing their normal biological functions. The common perception that chaperones are primarily concerned with protein folding is incorrect. The first protein to be called a chaperone assists the assembly of nucleosomes from folded histones and DNA and such assembly chaperones, especially in the nucleus, are concerned with the assembly of folded subunits into oligomeric structures.
hormone response element (HRE)
A hormone response element (HRE) is a response element for hormones, a short sequence of DNA within the promoter of a gene that is able to bind a specific hormone receptor complex and therefore regulate transcription.[1] The sequence is most commonly a pair of inverted repeats separated by three nucleotides, which also indicates that the receptor binds as a dimer.
retinoid X receptor (RXR)
The retinoid X receptor (RXR)[1] is a type of nuclear receptor which is activated by 9-cis retinoic acid.[2] There are three retinoic acid receptors (RXR), RXR-alpha, RXR-beta, and RXR-gamma encoded by the RXRA, RXRB, RXRG genes respectively.
Heat shock proteins (HSP)
Heat shock proteins (HSP) are a group of proteins whose expression is increased when the cells are exposed to elevated temperatures or other stress. This increase in expression is transcriptionally regulated. This dramatic upregulation of the heat shock proteins induced mostly by Heat Shock Factor (HSF) is a key part of the heat shock response.
chaperones
In molecular biology, chaperones are proteins that assist the non-covalent folding/unfolding and the assembly/disassembly of other macromolecular structures, but do not occur in these structures when the latter are performing their normal biological functions. The common perception that chaperones are primarily concerned with protein folding is incorrect. The first protein to be called a chaperone assists the assembly of nucleosomes from folded histones and DNA and such assembly chaperones, especially in the nucleus, are concerned with the assembly of folded subunits into oligomeric structures.
hormone response element (HRE)
A hormone response element (HRE) is a response element for hormones, a short sequence of DNA within the promoter of a gene that is able to bind a specific hormone receptor complex and therefore regulate transcription.[1] The sequence is most commonly a pair of inverted repeats separated by three nucleotides, which also indicates that the receptor binds as a dimer.
retinoid X receptor (RXR)
The retinoid X receptor (RXR)[1] is a type of nuclear receptor which is activated by 9-cis retinoic acid.[2] There are three retinoic acid receptors (RXR), RXR-alpha, RXR-beta, and RXR-gamma encoded by the RXRA, RXRB, RXRG genes respectively.
суббота, 15 марта 2008 г.
Food for Thoughts!!
ခုတစ္ေလာ ေခါင္းထဲမွာ အေတြးေတြ ေခ်ာက္ေအာင္ လာလာစားေနတဲ႔ အသံုးအႏွဳန္းေတြပါ။ အရွည္ကိုေတာ႔ မလုိက္ႏိုင္ေသးလို႔ အဓိပၸါယ္ဖြင္႔ဆိုခ်က္တစ္ခ်ိဳ႔ကို တင္လိုက္ပါတယ္။ အသံုး၀င္ႏိုင္ပါေစ။
What is Polymerization?
Without polymers, mankind couldn't exist. People use manmade plastics such as polypropylene and polyvinyl chloride (i.e., PVC) in hospitals, schools and their own homes. Yet, man-made plastic accounts for only a small percentage of polymers. Rubber and cellulose, which are natural polymers, are used to make everything from tires to cellophane to rayon. Deoxyribonucleic acid (i.e., DNA) and protein are also natural polymers.
As important as polymers are, they wouldn't exist without monomers, which are small, single molecules such as hydrocarbons and amino acids. These monomers bond together to form polymers. The process by which these monomers bond is called polymerization.
Allele
One of the variant forms of a gene at a particular locus, or location, on a chromosome. Different alleles produce variation in inherited characteristics such as hair color or blood type. In an individual, one form of the allele (the dominant one) may be expressed more than another form (the recessive one).
Pseudogene
A sequence of DNA that is very similar to a normal gene but that has been altered slightly so it is not expressed. Such genes were probably once functional but over time acquired one or more mutations that rendered them incapable of producing a protein product.
Crossing over
The term coined by Morgan and Cattell (1912) for the occurrence of new combinations of linked characters. With the acceptance of the chromosome theory, the term is applied to the breaking during meiosis of one maternal and one paternal chromosome, the exchange of corresponding sections of DNA, and the rejoining of the chromosomes. This process can result in an exchange of alleles between chromosomes and gives rise to new character combinations. Compare recombination.
Gene Conversion
A meiotic process of directed change in which one allele directs the conversion of a partner allele to its own form. In asci of Ascomycete fungi a 4:4 ratio of alleles is expected after meiosis, yet 6:2 and 5:3 ratios are sometimes observed. A model of recombination, produced by Holliday, suggests that gene conversion may be explained by repair of heteroduplex DNA.
Genomic imprinting
Genomic imprinting is a genetic phenomenon by which certain genes are expressed in a parent-of-origin-specific manner. Imprinted genes are either expressed only from the allele inherited from the mother (eg. H19 or CDKN1C), or in other instances from the allele inherited from the father (eg. IGF2). Forms of genomic imprinting have been demonstrated in insects, mammals and flowering plants.
What is Polymerization?
Without polymers, mankind couldn't exist. People use manmade plastics such as polypropylene and polyvinyl chloride (i.e., PVC) in hospitals, schools and their own homes. Yet, man-made plastic accounts for only a small percentage of polymers. Rubber and cellulose, which are natural polymers, are used to make everything from tires to cellophane to rayon. Deoxyribonucleic acid (i.e., DNA) and protein are also natural polymers.
As important as polymers are, they wouldn't exist without monomers, which are small, single molecules such as hydrocarbons and amino acids. These monomers bond together to form polymers. The process by which these monomers bond is called polymerization.
Allele
One of the variant forms of a gene at a particular locus, or location, on a chromosome. Different alleles produce variation in inherited characteristics such as hair color or blood type. In an individual, one form of the allele (the dominant one) may be expressed more than another form (the recessive one).
Pseudogene
A sequence of DNA that is very similar to a normal gene but that has been altered slightly so it is not expressed. Such genes were probably once functional but over time acquired one or more mutations that rendered them incapable of producing a protein product.
Crossing over
The term coined by Morgan and Cattell (1912) for the occurrence of new combinations of linked characters. With the acceptance of the chromosome theory, the term is applied to the breaking during meiosis of one maternal and one paternal chromosome, the exchange of corresponding sections of DNA, and the rejoining of the chromosomes. This process can result in an exchange of alleles between chromosomes and gives rise to new character combinations. Compare recombination.
Gene Conversion
A meiotic process of directed change in which one allele directs the conversion of a partner allele to its own form. In asci of Ascomycete fungi a 4:4 ratio of alleles is expected after meiosis, yet 6:2 and 5:3 ratios are sometimes observed. A model of recombination, produced by Holliday, suggests that gene conversion may be explained by repair of heteroduplex DNA.
Genomic imprinting
Genomic imprinting is a genetic phenomenon by which certain genes are expressed in a parent-of-origin-specific manner. Imprinted genes are either expressed only from the allele inherited from the mother (eg. H19 or CDKN1C), or in other instances from the allele inherited from the father (eg. IGF2). Forms of genomic imprinting have been demonstrated in insects, mammals and flowering plants.
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