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CRISPR-Gene Editing, Key Components, Applications, Challenges

Context: Casgevy and Lyfgenia (two cell-based gene therapies) have been approved by the Food and Drug Administration (FDA) for sickle cell anaemia treatment and beta-thalassemia utilising the CRISPR/Cas 9 genome editing technology.

About CRISPR-Gene Editing

  • Basis for this technology: Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR), a feature of the bacterial immune system.
    • It acts as a genetic memory bank, storing fragments of viral DNA from past infections to bolster future defences.
    • When bacteria encounter previously encountered viruses, the CRISPR system enables them to recognize and eliminate these threats, effectively immunising the bacteria.
  • Two key components:
    • Cas9, an enzyme acting as ‘molecular scissors‘ to cut DNA at specific locations.
    • Guide RNA (gRNA), designed to direct Cas9 to a precise genome spot.
      • The gRNA binds to a matching DNA sequence, guiding Cas9 to make strategic cuts.
    • Cells then attempt to repair this DNA break, allowing scientists to manipulate genes by adding, removing, or altering DNA segments.
  • Applications: Treating genetic diseases, enhancing crop resilience to drought, improving food crop traits, and exploring the potential for bringing extinct species like the woolly mammoth and the dodo back to life.

CRISPR - Gene Editing

Challenges Associated with CRISPR Technology

  • Health Equity and Disparities: The potential for CRISPR to exacerbate existing health inequities due to uneven access to advanced treatments across different socioeconomic groups.
  • Moral and Ethical Concerns of Germline Editing: The ethical dilemma of making heritable changes to individuals, questioning the morality of altering the genetic makeup of future generations to treat genetic conditions.
  • Regulatory Restrictions: Current restrictions limit genome editing to somatic cells, with a moratorium on germline editing due to the complex ethical, societal, and safety concerns.
  • Scientific Overreach: Instances like the controversial experiment by Chinese scientist He Jiankui, who edited healthy embryos, highlight the risks of scientists bypassing ethical guidelines and the lack of clear outcomes from such interventions.
  • Long-term Effects Uncertainty: The long-term consequences of CRISPR editing are not fully understood, raising concerns about unforeseen impacts on individuals and subsequent generations.
  • Accessibility and Affordability: The risk of gene editing technologies becoming exclusive to the wealthy, potentially leading to a societal divide based on genetic enhancements and therapeutic uses.
    • g. Casgevy costs $ 2.2 million per patient to treat sickle-cell anemia.

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Important Terminology

Germline Editing

  • Germline editing refers to the process of making changes to the genome in the germline cells of an organism.
  • Germline cells are the reproductive cells (sperm and eggs in animals, pollen and ovules in plants) that pass on genetic information to offspring.

Somatic Cells

  • Somatic cells are any cells forming the body of an organism, excluding the reproductive cells (germline cells).
  • In humans and other multicellular organisms, somatic cells make up the majority of the body, including cells that form the skin, bones, blood, and internal organs

Sickle-cell Anaemia

  • Sickle-cell anaemia (SCA) is a genetic blood disorder characterised by red blood cells that assume a sickle or crescent shape due to abnormal haemoglobin, compromising their oxygen transport capabilities.

CRISPR Technology Impact in Indian Context

Challenges

  • Limited healthcare access: Tribal populations suffering from sickle cell anaemia often reside in remote areas with scarce healthcare professionals, hindering primary care and diagnosis.
  • Equity and affordability: Concerns exist about wealthy individuals exploiting the technology while marginalised communities lack access due to cost or infrastructure limitations.

Potential Applications

  • Sickle Cell Anemia Elimination Mission: Launched in 2023, this government initiative aims to strengthen healthcare systems and improve access to primary, secondary, and tertiary care for affected populations.
  • Gene editing as a therapeutic tool: CRISPR could potentially offer curative treatments for sickle cell anaemia, addressing the limitations of current management strategies.
PYQ
Q. What is cas9 protein that is often mentioned in the news? (2019)

(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 generally modified crops

Answer: Option (a)

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