Transgenic Plants – Gene Construct and Vectors | Iken Edu



transgenic plants introduction gene construct and vectors for several years farmers have been altering the genetic makeup of the crops that accrue several bio technological approaches such as hybridization mutagenesis and polyploidy are available for the crop improvement but the most potent approach is the genetic engineering or genetic modification the plants obtained through genetic engineering contain a gene or genes usually from an unrelated organism such genes are called trans genes and the plants containing trans genes are known as transgenic plants or genetically modified plants or GMP transgenic plants were first created in the early 1980s by four groups working independently at Washington University in st. Louis Missouri the Richter University in Kent Belgium Monsanto Company in st. Louis Missouri and the University of Wisconsin the Washington University group produced sales of nicotiana plumb bajina folia a close relative of ordinary tobacco that were resistant to the antibiotic kanamycin Jeff Schell and Marc van Montagu working in Belgium had produced tobacco plants that were resistant to kanamycin and to methotrexate a drug used to treat cancer and humanoid arthritis robot Frawley Steven Rogers and Robert Hodge at Monsanto had produced petunia plants that were resistant to kanamycin similarly the Wisconsin group headed by john kemp and timothy hall had inserted a beam gene into a sunflower plant these early transgenic plants were laboratory specimens but subsequent research has developed transgenic plants with commercially useful traits such as resistance to herbicides insects and viruses let us understand how transgenic plants are made firstly it is necessary to obtain the desired gene the desired gene is identified isolated and cloned this gene undergoes certain modification before it can be effectively inserted into a plant a promoter sequence is added in the gene to ensure the genes efficient expression in plant cells the promoter is an on/off switch that controls when and where in the plant the gene will be expressed the most commonly used promoter is CA MV 3 5 s from the cauliflower mosaic virus which generally results in a high degree of expression in plants expression of genes is confined to specific tissues such specificities in gene expression are due to certain DNA sequences called enhancers or silences and enhance increases the gene expression while a silencer suppresses the gene expression for example the BT gene for insect resistance is of bacterial origin and has a higher percentage of 18 nucleotide pairs compared to plants which prefer GC nucleotide pairs in a clever modification researchers substituted 18 nucleotides with GC nucleotides in the BT gene without significantly changing the amino acid sequence the result was enhanced production of the gene product in plant cells you a reporter gene or a selectable marker gene is added to the gene construct to identify plant cells which have successfully integrated the trans gene selectable marker gene encode proteins that provide resistance to compounds which are normally toxic to plants for example herbicides antibiotics only plant cells that have integrated the selectable marker gene will survive when grown on a specific medium containing appropriate herbicide or antibiotic at the end of the gene coding sequence of the gene construct a termination sequence or the chain termination codon is added it is either tae taa or TGA this sequence is then followed by a non transcribed region and polyadenylation site which denotes the end of the transcription once the trans gene is ready it is inserted into a vector a vector is a circular DNA molecule capable of independent existence and replication a vector molecule is cut at two ends with the help of restriction enzyme and the trans gene is inserted and sealed with a vector molecule by using ligase enzyme the vector is then introduced into the plant cell the main purpose of vectors is the controlled expression of a trans gene inside the host cell different vectors are used in making of transgenic plants such as plasmid vectors cauliflower mosaic virus or CMV tobacco mosaic virus or tmv gemini virus bro mosaic virus or bmv

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