Gene silencing is an epigenetic process that reduces or eliminates the production of a protein from its corresponding gene. There are two main types: transcriptional gene silencing via histone modifications, and post-transcriptional gene silencing by destroying or blocking mRNA. Methods to induce gene silencing include antisense oligonucleotides, ribozymes, and RNA interference using short interfering RNA or microRNA. RNAi leads to sequence-specific degradation of mRNA through the RNA-induced silencing complex. Gene silencing has applications in studying gene function, functional genomics, and medicine, with the goal of downregulating gene expression.

1. GENE SILENCING
NAME : ANAGHA AMAR PISAL
M.Sc BIOTECHNOLOGY - 1

2. INTRODUCTION
• Epigenetic process of gene regulation
• Aims to reduce or eliminate the production of
protein from its corresponding gene
• It is same as gene knock down but totally
different form gene knock out

3. Types
• Transcriptional gene silencing -
results in histone modifications
• Post transcriptional gene silencing –
results from mRNA of a particular gene being
destroyed or blocked

4. Transcriptional silencing
• Genome imprinting :
genetic phenomenon in which genes are
expressed in parent or origin specific manner
• Paramutation :
interaction between two alleles of a single locus
• Position effect :
due of translocation of gene eg. Drosophila :
position effect variegation
• RNA directed DNA methylation
• Transposon silencing

6. Gene silencing methods used in
research
• Antisense oligonucleotides :
bind to complementary target molecules
• Ribozymes :
catalytic activity inhibit gene expression

7. RNA interference (post-transcriptional
gene silencing)
• Exogenous dsRNA is induced which binds to
known complementary mRNA
• Cellular mechanism that degrades the unwanted
mRNA in the cytoplasm
• Sequence specific RNA degradation
• dsRNA can be
1. siRNA
2. miRNA

8. miRNA
• RNA molecules, 22–25 nucleotides
• miRNAs are produced by Dicer from the precursors
of ~70 nucleotides (pre-miRNAs)
• Processed through at least two sequential steps:
(i) generation of the ~70 nucleotide
precursor microRNAs from the
longer transcripts (termed primiRNAs);
(ii) processing of pre-miRNAs into
mature miRNAs.

10. siRNA
• double stranded RNA from exogenous sources like
viruses, transgenes or transposons, i.e;
they originate from double stranded RNAs.
• 21–23 nucleotide-long double-stranded RNA
• result from the Dicer enzyme cutting up a larger
fragment of perfectly complimentary double
stranded RNA
• RISC and serve as a guide to recognition of
complementary base pairing on target mRNA

12. Anti sense RNA technology
• Antisense RNA has the opposite
sense to m RNA.
• The presence of complimentary
sense and antisense RNA
interferes with gene expression
at the level of RNA processing or
possible translation.
• This technology widely used in
plants for gene inhibition.

13. Applications
• Biological functions
1. Downregulation of genes: important in
translational repression and in the
regulation of development
2. Upregulation of genes: dubbed RNA activation
3. Evolution: The ancestral function of the RNAi
system is generally agreed to have been
immune defense against exogenous genetic
elements such as transposons and viral
genomes

14. • Technological applications
1. Gene knockdown: to study the function of genes
in cell culture and in vivo in model organisms
2. Functional genomics: particularly attractive
technique for genomic mapping
3. Medicine: use of short interfering RNA mimics;
seen as a promising way to treat cancer by
silencing genes differentially
upregulated
4. Biotechnology : Flavr Savr tomato and two
cultivars of ringspot-resistant papaya, were
originally developed using antisense
technology.

16. THANK YOU !