Mutation is the change in the DNA sequence of cell genome which are heritable. It causes various changes in the gene number and the chromosomal number of the genome which causes due the mutagen. Mutagen cause manipulations in the genetic material duringcell division either by exposuring to ultravioletorionizing radiation,mutagenic chemicals, orviruses.
Mutations are the heritable changes in the genome. Some mutations may cause changes in the phenotypic characteristics of the gene expression. In microbial organisms they are designated as wild-type strains and agents that cause mutations are called as mutants. Therefore, mutants are characterized by the inherited differences between them and their ancestral wild-type strains. Variant forms of a specific genetic determinant are called alleles. Genotypic symbols are lower case, italicized specify individual genes with a (+) superscript indicating the wild type allele were as phenotypic symbols are capitalized and not italicized. For example: to produce ß-galactosidase, in order to ferment lactose, the genotypic symbol used is lacZ+ and mutants not producing ß-galactosidase are lacZ. The lactose-fermenting phenotype is designated as Lac+ and inability to ferment lactose is Lac-.
CLASSIFICATION ON BASIS OF SELECTION:-
Mutation are classified as selectable and unselectable :-
- A selectable mutation is that mutation in which there is a growth and survivality under a specific environment conditions where the mutant can grow and wild type will die.
- An unselectable mutant requires a cell by cell examination in order to find a mutant with desirable characteristics.
- Selection can be direct or indirect :-the indirect selection is used for isolating mutant that is deficient in producing a necessary growth factor. Like E.coli can grow on glucose and mineral salts more than lactic acid.
RELATED RESEARCH ARTICLES:
MULTIPLE BIOCHEMICAL ACTIVITIES OF NM23/NDP KINASE IN GENE REGULATION :-
Department of Molecular Biology, Princeton University, Princeton, New Jersey, 08546-5414
NM23/NDPk protein play an important role in the cancer and the development.These proteins play a role in the DNA metabolism including, binding of the nucleotide and the transcription and the cleavage of the DNA strands using covalent DNA complexes. DNA cleavage reaction of NM23/NDPk is characteristics of DNA repair enzymes. It is seen that both DNA cleavage and the NDPk reactions are conserved between E.coli and te human beings. NM23/NDP kinases are regulators of gene expression during development and the cancer via unrecognized pathways and mechanism of genetic control and unrecognized role in DNA repair and recombination.
The Parkinson disease causing LRRK2 mutation I2020T is associated with increased kinase activity :-
Christian Johannes Gloeckner,Norbert Kinkl,Annette Schumacher,Ralf J. Braun,Eric O'Neill,Thomas Meitinger,Walter Kolch,Holger Prokisch andMarius Ueffing
Parkinson disease is the most common neurodegenerativedisorder. Recent studies have shown that mutations in theleucine-richrepeat kinase2 gene, located on the chromosomalregionis the cause for the disorder named as Parkinson disease. The LRRK2 protein consistsof multiple domainscontains a predicted kinase domain, with homologyto MAP kinases. Using cell fractionation and immuno fluorescencemicroscopy, visualized that LRRK2 is located in the cytoplasmwhich is associated with cellular membrane structures. LRRK2 protein shows the autokinase activity. The disease-associated I2020T mutant shows a significant increase in the autophosphorylationofwild-type proteinin vitro. This suggeststhat the PD is caused by the I2020T mutation which is associatedwith an increase rather than a loss in LRRK2 kinase activity.
Mediator protein mutations that selectively abolish activated transcription:-
The deletion of any one of three subunits of yeast mediator as ( Med2, Pgd1 (Hrs1), and Sin4) of transcriptional regulation terminated the activation by Gal4-VP16. Other mediators functions like the stimulation of basal transcription and of TFIIH kinase activity were remain unaffected. The overlapping Mediator subunit was found for activation by Gcn4. So, the genetic requirements for activationin vitrowere closely related with thosein vivo. A whole genome expression of a?med2strain showed diminished transcription of a subset of inducible genes but that show only minor effects on basal transcription. These findings make an important connection between transcriptional activationin vitroandin vivo and identify Mediator as a "global" transcriptional co activator.
DNA gyrase and topoisomerase IV: biochemical activities, physiological roles during chromosome replication, and drug sensitivities :-
DNA gyrase and topoisomerase IV are two topoisomerases present in the bacteria. They play crucial role in the cell. Topoisomerase gyrase is involved in the chain elongation during the replication of the chromosome whereas topoisomerase IV separates the linked daughter chromosomes during the terminal stage of DNA replication. The different roles can be attributed to the various biochemical properties of the two enzymes. Therefore, biochemical activities, physiological roles, and drug sensitivities of the enzymes are reviewed and studied using gyrase and the topoisomerase.
NATURALSELECTION AND THE EMERGENCE OF AMUTATION PHENOTYPE:
An Update of the Evolutionary Synthesis Considering Mechanisms that Affect Genome Variation :-
In evolution it is assume that the mutations are random with respect to their potential effects on survivality. The phenotypic variations that affect the survivality of the descendants, intrinsic variations and the location of genetic change is under natural selection. Through the action of natural selection on the genes, favorable mutations can become more probable than random.From the example: the variation in bacterial surface proteins to the vertebrate immune response it is seen that a genetic change is better than random with respect to its potential effect on survival. However, some potentialy mutations are so probable that they can be viewed as being encoded in the genome. An updated evolutionary theory includes emergence under selective pressure of genomic information that affects the probability of different types of mutation that results into the genomic survival.