Context:
Scientists discovered naturally occurring human DNA editing tool – Bridge Recombinase Mechanism.
Bridge Recombinase Mechanism:
- It utilizes mobile genetic elements or “jumping genes”, which cut and paste themselves into genomes, performing on-the-go DNA manipulation and are present in all forms of life.
- Extra DNA at the ends of jumping genes gets joined together and converts the DNA double helix structure into a single-stranded RNA molecule.
- This bridge RNA molecule can bind to two DNA segments (donor and target), allowing for flexible DNA modifications.
- Donor and target loop can be programmed independently, offering great flexibility in inserting or recombining sequences to DNA.
- A guide can be used to efficiently program the jumping gene, which can then precisely insert itself into user-defined genomic locations.
Jumping Genes are small DNA segments with a recombinase enzyme (transposases) along with extra DNA segments at the ends of the genes that binds and manipulates DNA.
Significance of the discovery:
- It will allow researchers to rearrange, recombine, invert, duplicate, move, and perform other editing operations on very long DNA sequences.
- It can lead to development of more advanced gene editing therapeutics and treatments for diseases.
- It increases the diversity of nucleic-acid-guided systems beyond RNA interference and CRISPR.
How RNA bridge differs?
| RNA bridge | CRISPR |
| Consists of a recombinase protein that hooks up with a guide RNA, like the CRISPR Cas9. Unlike CRISPR, the guide RNA specifies two DNA sequences to seek out, not just one. One sequence specifies the target site in the genome to be altered, just as in CRISPR. The other specifies the DNA to be altered. This system can add, delete, or reverse DNA sequences of virtually any length. | There are two parts to the standard CRISPR Cas9 protein. One-part links with a guide RNA molecule and seeks out any DNA that matches a certain section of the guide RNA. The second part of CRISPR Cas9 is a cutter that severs DNA once the Cas9 has bound to its target site. |
Other Gene-editing technologies:
- CRISPR-Cas9: It is a customizable tool that lets scientists cut and insert small pieces of DNA at precise areas along a DNA strand.
- TALE nucleases: Nucleases that cleave unique genomic sequences in living cells can be used for targeted gene editing.
- Zinc-finger nucleases: Targeted to cleave a chosen genomic sequence and provokes cellular repair processes that in turn mediate efficient modification of the targeted location.
- RNA interference (RNAi): Targets RNA molecules to block or activate gene expression.
Source: The Print
Previous Year Question
What is Cas9 protein that is often mentioned in news?
[UPSC Civil Services Exam – 2019 Prelims]
(a) A molecular scissors used in targeted gene editing
(b) A biosensor used in the accurate detection of pathogens in patients
(c) A gene that makes plants pest-resistant
(d) A herbicidal substance synthesized in genetically modified crops
Answer: (a)
