siRNA Vs. miRNA - Important Differences

RNA (Ribonucleic acid) is involved in the synthesis of proteins and is essential for gene expression and biological coding in all living entities. There are three main types of RNA – rRNA, mRNA, tRNA involved in transferring codon, protein synthesis and provision of translation site.

The non-coding smaller RNAs are vital to the process of gene silencing and participate in the mechanism of gene regulation, referred to as RNAi or RNA interference. RNA interference is the sequence-specific mRNA degradation procedure regulating the expression of genes.

The double-stranded siRNA is also referred to as short interfering RNA or silencing RNA. The miRNA (Micro RNA) is a non-coded molecule. miRNA and siRNA are proteomic tools, finding their use to study different facets of expression of genes.

siRNA and miRNA

The RNA interference process can be mediated by miRNA or siRNA. Both of these are processes in the cell by the dicer enzyme and integrated into the RISC complex.

siRNA is deemed as exogenous double-stranded RNA consumed by cells, through viruses as vectors. These vectors come into play when fragments of DNA are used in cloning a gene for the production of a GMO (genetically modified organism).

miRNA is considered to be single-stranded derived from endogenous non-coding RNA. Such RNA is seen in the introns of huge molecules of RNA. While the association of siRNA to its target animal is said to be a perfect match for the sequence, miRNA can show the translation of some different mRNA sequences, as their pairing is imperfect.

Key Differences between siRNA and miRNA

The table below depicts the differences between siRNA and miRNA.

siRNA

miRNA

Nature of RNA

Exogenous

Endogenous

Number of strands

Double-stranded

Single-stranded

Occurrence

Can be seen in lower animals and plants, not observed in mammals

Seen in all plants and animals

Structure

These are 21-23 nucleotide long RNA duplexes possessing dinucleotide 3’ overhang

These are 19-25 nucleotide RNA hairpin forming duplex by associating with each other.

Pairing

A perfect pairing, highly specific having one mRNA target only

Imperfect pairing can inhibit the translation of many mRNA targets

Requirement of gene silencing

Ago 2 protein- argonaute protein 2 required

Ago protein only, not necessarily the Ago2. Any protein from the argonaute family can participate in the miRNA-mediated gene silencing

Regulatory structures

Regulates the expression of varying genes

Regulates the expression of genes that are alike or those genes having the same origin

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