Key Concepts in Biotechnology: GM Crops and Enzymes

Posted on Oct 20, 2025 in Biology

BT Cotton: A Genetically Modified Crop

BT cotton is a genetically modified (GM), pest-resistant cotton variety. It is modified by inserting one or more genes from Bacillus thuringiensis (a common soil bacterium) which produces an insecticide to combat bollworms. This information is crucial for understanding biotechnology topics relevant to competitive examinations like the IAS exam.

Key Facts about BT Cotton

  • BT cotton is the only GM crop approved for commercial cultivation in India (since 2002) by the Genetic Engineering Appraisal Committee (GEAC) under the Ministry of Environment, Forest and Climate Change.
  • Long-term studies conducted by ICAR (Indian Council of Agricultural Research) showed no adverse effects on soil, microflora, or animal health.
  • Bacillus thuringiensis produces Cry proteins. These proteins, present in BT cotton plants, are effective at killing bollworm and tobacco budworm larvae—two major caterpillar pests of cotton.
  • The global BT cotton market is driven by the increased demand for reducing worker and environmental exposure to chemical pesticides.

Generations of BT Cotton: BT I and BT II

The Government of India (GoI) permitted commercial cultivation in two main generations:

  • BT I Cotton (2002): The first generation was introduced primarily to prevent insect attacks.
  • BT II Cotton (2006): The second generation was launched by combining two Bacillus thuringiensis (Bt) proteins—Cry1Ac + Cry2Ab—specifically targeting the pink bollworm, a common pest in India.

Adoption of Bt cotton rose significantly, reaching 81% in 2007 and 93% in 2011. Currently, Bt cotton accounts for more than 90% of cotton fields in India.

Significance and Benefits of BT Cotton

Since its introduction in India, the area, production, and productivity of BT cotton have increased significantly. Key benefits include:

  • Increased Production: Cotton production rose from 14 million bales in the pre-Bt year (2001–02) to 39 million bales in 2014–15, an increase of almost 180%.
  • Higher Yield: High yields are attributed to the effective control of bollworms.
  • Reduced Pesticide Use: There has been a drastic reduction in the application of chemical insecticides for bollworm control.
  • Economic Gains: It has led to higher profits for farmers.
  • Environmental Conservation: It has resulted in the conservation of biological control agents and other beneficial organisms.

Disadvantages and Challenges of BT Cotton

  1. High Seed Cost: BT cotton seeds are more expensive than local, non-genetically modified varieties.
  2. Need for New Stock: Seeds cannot be re-used, requiring farmers to buy new stock for every growing season.
  3. Pest Resistance: The pink bollworm, a major cotton pest, developed resistance to BT cotton in four states in India. This was the world’s first recorded instance of resistance to BT cotton. To combat this, Monsanto Corporation developed the second-generation seed combining two BT proteins.

Golden Rice: Addressing Vitamin A Deficiency

Golden Rice is a genetically engineered rice variety designed to combat Vitamin A Deficiency (VAD). It contains beta-carotene (provitamin A), a plant pigment that the body converts into Vitamin A as needed. This compound gives the grain its characteristic yellow-orange or golden color.

Development and Nutritional Value

Golden Rice was developed through genetic engineering. Although ordinary rice plants produce beta-carotene, it is not present in the grain itself. Scientists used genetic modification to add this compound to the grain, significantly improving its nutritive value. This modification was achieved by adding two new enzymes.

The beta-carotene found in Golden Rice is identical to the beta-carotene found naturally in:

  • Green leafy and yellow-colored vegetables.
  • Orange-colored fruits.
  • Many vitamin supplements and food ingredients.

Agronomic Performance and Impact

Golden Rice does not require special cultivation practices and generally exhibits the same yield and agronomic performance as ordinary rice.

Vitamin A deficiency (VAD) remains a major public health issue, particularly in communities where access to diverse, affordable, and available vitamin A sources (like supplements or varied diets) is limited. Since rice is a staple food in many VAD-affected communities in Asia, Golden Rice offers a significant opportunity to improve Vitamin A status once it is widely available for public consumption.

Human Growth Hormone (HGH) and Somatotropin

Human Growth Hormone (HGH), also known as somatotropin, is a natural hormone produced and released by the pituitary gland. It acts on many parts of the body, primarily promoting growth in children.

Function of HGH

While HGH ceases to increase height once the growth plates in the bones (epiphyses) have fused, the body still requires it throughout life. After growth is complete, HGH helps to maintain:

  • Normal body structure.
  • Metabolism, including keeping blood sugar (glucose) levels within a healthy range.

Hormones and the Pituitary Gland

Hormones are chemical messengers that coordinate various bodily functions by traveling through the blood to organs, muscles, and other tissues. These signals dictate bodily actions and timing. The human body produces over 50 hormones, which interact in complex processes.

The Pituitary Gland

The pituitary gland is a small, pea-sized endocrine gland situated at the base of the brain, beneath the hypothalamus. It consists of two lobes:

  • Anterior (Front) Lobe: Responsible for producing HGH.
  • Posterior (Back) Lobe.

Regulation by the Hypothalamus

The pituitary gland is connected to the hypothalamus via the pituitary stalk (a structure of blood vessels and nerves). The hypothalamus, which controls functions like blood pressure, heart rate, body temperature, and digestion, communicates with the pituitary gland to regulate hormone release:

  • Growth Hormone-Releasing Hormone (GHRH): Stimulates the pituitary gland to release HGH.
  • Somatostatin: Inhibits the release of HGH.

Clinical Use of HGH

Healthcare providers utilize a synthetic form of HGH (sometimes called recombinant HGH) to treat specific health conditions, such as growth hormone deficiency. It is crucial never to take synthetic HGH without a prescription from a healthcare provider.

DNA Ligase: Essential Enzyme for Genomic Integrity

DNA ligases are a fundamental class of enzymes necessary for all organisms to maintain the structural integrity of the genome. This enzyme acts as molecular glue, connecting two strands of DNA together by forming a bond between the phosphate group of one strand and the deoxyribose group of the other strand.

Function and Mechanism

The primary importance of DNA ligases lies in maintaining genomic integrity by joining breaks in the DNA’s phosphodiester backbone. These breaks occur during:

  • Recombination.
  • DNA replication.
  • DNA damage and subsequent repair.

Breaks in the phosphate backbone compromise genomic stability, potentially leading to the loss of genetic content and the introduction of deleterious chromosomal mutations.

The catalytic activity of DNA ligases repairs these breaks by forming phosphodiester bonds between adjacent nucleotides in duplex DNA. This activity requires a nucleotide cofactor and follows a unique three-step reaction mechanism involving covalent modification of both the DNA substrate and the ligase enzyme.

Role in DNA Replication

DNA replication involves several enzymes working together. Replication is initiated by the primase enzyme introducing an RNA primer. DNA polymerase then adds nucleotides to the primer’s 3′ end on the leading strand. On the lagging strand, replication proceeds discontinuously through the synthesis of Okazaki fragments.

The crucial role of DNA ligase in replication is to join these fragments. Once the RNA primer is removed and replaced with DNA nucleotides by DNA polymerase, gaps remain between the fragments. DNA ligase fills these gaps by producing phosphodiester links, effectively joining the 5′ end of one strand to the 3′ end of the adjacent strand.

Applications in Biotechnology (Ligation)

DNA ligase is widely used in molecular biology, a process referred to as ligation. It can be used for:

  • Introducing genes of interest into plasmid vectors.
  • Creating fusion genes by uniting one gene into another.

Ligation can be performed on DNA lengths that have either sticky ends or blunt ends following restriction digests. In blunt-end ligation, the DNA fragments are joined directly by the DNA ligase.