RNA interference (RNAi) is a cellular process that regulates gene expression through the degradation or inhibition of target mRNA. The steps involved are as follows:
1. Activation of RNase III-like enzyme Dicer (B): The RNAi pathway begins with the activation of the enzyme Dicer, which processes long double-stranded RNA (dsRNA) molecules into small interfering RNAs (siRNAs)
2. Formation of small interfering RNAs (siRNAs) (A): Dicer cleaves dsRNA into siRNAs, which are approximately 21–23 nucleotides in length with 2-nucleotide overhangs at their 3' ends.
3. Inactivation of target RNA (C): The siRNAs are incorporated into the RNA-induced silencing complex (RISC), where they guide the complex to complementary mRNA sequences.
4. Formation of RISC complex (D): The RISC complex, containing Argonaute proteins, binds the siRNAs, facilitating the recognition and cleavage of the target mRNA, thereby inactivating it.
List I | List II |
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(A) Radiation hybrid mapping | (I) DNA can be cut into large fragments and circularized for use in chromosome walking |
(B) Sequence tagged site (STS) mapping | (II) Useful for cloning of overlapping DNA fragments (restricted to about 200 kb) |
(C) Chromosome jumping | (III) Fragment genome into large pieces and locate markers and genes |
(D) Chromosome walking | (IV) Applicable to any part of DNA sequence if some sequence information is available |