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GENE SILENCING Copyright of all the photographs and other material lies with the original developer / author. These have been used for educational use only and not for any commercial purpose

Definitions on the web : 

Definitions on the web Definitions of Gene silencing on the Web: Targeting or interfering with a specific gene and preventing its Preventing or suppressing genes being translated into Gene silencing is the inhibition of gene expression—that is, transcriptional repression. A reciprocal relationship exists between the density of The process(es) whereby certain genes in the genome are prevented from being expressed by chemical modifications and other refers to the normal process of "switching off" the gene, which would be otherwise active. Gene silencing is a normal process and is used to regulate endogenous genes. This process also appears to protect the genome from transposons and viruses. Read Gene silencing is a general term describing epigenetic processes of gene regulation. The term gene silencing is generally used to describe the silencing Any technique or mechanism in which the expression of a gene is prevented silencing

Gene silencing : 

Gene silencing From Wikipedia, the free encyclopedia Jump to: navigation, search Gene silencing is a general term describing epigenetic processes of gene regulation. The term gene silencing is generally used to describe the "switching off" of a gene by a mechanism other than genetic modification. That is, a gene which would be expressed (turned on) under normal circumstances is switched off by machinery in the cell. Genes are regulated at either the transcriptional or post-transcriptional level. Transcriptional gene silencing is the result of histone modifications, creating an environment of heterochromatin around a gene that makes it inaccessible to transcriptional machinery (RNA polymerase, transcription factors, etc.).

Gene silencing : 

Gene silencing Post-transcriptional gene silencing is the result of mRNA of a particular gene being destroyed. The destruction of the mRNA prevents translation to form an active gene product (in most cases, a protein). A common mechanism of post-transcriptional gene silencing is RNAi. Both transcriptional and post-transcriptional gene silencing are used to regulate endogenous genes. Mechanisms of gene silencing also protect the organism's genome from transposons and viruses. Gene silencing thus may be part of an ancient immune system protecting from such infectious DNA elements. Genes may be silenced by DNA methylation during meiosis, as in the filamentous fungus Neurospora crassa.

Slide 5: 

© A.K. Chhabra How DNA/Gene produces phenotypes Transcription Translation Protein Synthesis

Antisense RNA Approach : 

Antisense RNA Approach

RNA interference : 

RNA interference RNA interference (RNAi) is a mechanism that inhibits gene expression at the stage of translation or by hindering the transcription of specific genes. RNAi targets include RNA from viruses and transposons (significant for some forms of innate immune response), and also plays a role in regulating development and genome maintenance. Small interfering RNA strands (siRNA) are key to the RNAi process, and have complementary nucleotide sequences to the targeted RNA strand. Specific RNAi pathway proteins are guided by the siRNA to the targeted messenger RNA (mRNA), where they "cleave" the target, breaking it down into smaller portions that can no longer be translated into protein. A type of RNA transcribed from the genome itself, microRNA (miRNA), works in the same way.

Flavr Savr tomato : 

Flavr Savr tomato The Flavr Savr tomato was genetically engineered by Calgene Inc. in 1994 to stay fresh on store shelves longer than regular tomatoes. It was the first genetically modified food on the market, and was developed by the then-local biotech start-up company that included many UC Davis professors. Mixed taste-test reviews came in and the Flavr Savr suffered from supply problems, marketing controversies and financial trouble. In 1996, Calgene was bought out by Monsanto and by 1998 the Flavr Savr was removed from supermarket shelves. Another locally bred tomato that is significantly more commercially successful is the Square Tomato.

square tomato : 

square tomato A "square tomato" is not actually square in shape any more than Coral Bells are made from coral or Baby Tears are related to crying infants. Instead, it is a type of tomato that was developed at UC Davis to pack into boxes better and ship with fewer losses (e.g., ripped or smashed tomatoes). Most of the tomatoes you find in the supermarket are square tomatoes.

Antisense RNA Approach : 

Antisense RNA Approach Silencing of target genes NEW PATHWAY DISCOVERED

Antisense RNA Approach : 

Antisense RNA Approach Silencing of target genes Figure 1. Schematic representation of the antisense gene cassette and RNAs encoded by plasmids of the pGW48 series. (A) The basic two unit antisense RNA cassette is shown. The positions of the promoter sequence, inhibitory unit and recognition unit respectively and relevant restriction sites are indicated. (B) RNAs encoded by plasmids of the pGW48 series are shown schematically. Sequences complementary to the lacI target RNA are indicated in red and sequences in sense orientation are blue. For simplicity, the entire ribozyme sequence is shown coloured, even though only the flanking sequences are complementary to the target.

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