What is?
Frequently, expression of trans-genes becomes suppressed in transgenic Plants after they have been grown for one or more generations, this is called gene silencing. this is often accompanied by DNA methylation of trans-genes, usually methylation of C occurs in the symmetrical CG and CNG (N= any one of the four DNA bases) sequences, but some times asymmetrical sequences are also methylated. In general, higher the number of copies of a trans-gene, more frequent is their hyper-methylation and trans-gene inactivation.
Types
Transcriptional silencing-
Post transcriptional silencing-
Transcriptional silencing is generally due to promoter methylation, other side post- transcriptional silencing can involve methylation of the coding sequence. the latter does not just affect transcription.gene silencing occurs most likely due to RNA transcript degradation.
Problems due to gene silencing
Transgenic silencing result in variable and, usually, unacceptable levels of trans-gene expression. this necessitates an extensive and often prolonged evaluation of transgenic lines. it may often become necessary to order suitable transgenic lines in hybridization and selection programmes in order to develop transgenic lines with stable and the desired level of trans-gene expression.
Both these steps require additional resources and, above all, time and delay the releases of transgenic lines as varieties. Finally in stability would causes problems in the registration of the varieties as they are required to be distinct, uniform and stable.
Gene Silencing In Plants, Gene Silencing In Crop Plants, Gene Silencing In Transgenic Plants, Gene Silencing, Gene Silencing Definition, Gene Silencing Notes
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