Why in the News?

In a major study, scientists proved that cold exposure in rice plants can cause changes that improve stress tolerance and are inherited by the next five generations, supporting Lamarck’s old theory.

How did later scientific discoveries challenge it?

• Weismann’s Tail-Cutting Experiment: August Weismann demonstrated that acquired traits are not inherited by cutting the tails of mice for five generations, yet their offspring were still born with tails.
• Mendel’s Laws of Heredity: Gregor Mendel showed that traits are inherited through stable units (genes) passed unchanged from parents to offspring, rather than traits acquired during life. Eg: In pea plants, traits like flower colour were inherited predictably, regardless of environmental changes.
• Discovery of DNA and Mutations: The discovery of DNA as the genetic material and that mutations cause heritable changes explained inheritance scientifically, without relying on acquired characteristics. Eg: Genetic disorders like sickle cell anemia are caused by specific DNA mutations, not by environmental use or disuse.

How did Mendel’s work and DNA discovery change heredity understanding?

• Introduction of Stable Hereditary Units: Mendel’s experiments introduced the concept of “genes” as stable, particulate units of inheritance passed from parents to offspring. Eg: Mendel’s pea plant experiments showed traits like seed shape and flower color followed predictable patterns.
• Law of Segregation and Independent Assortment: Mendel proposed that alleles segregate independently, ensuring genetic variation without influence from acquired traits. Eg: A plant with one tall and one short gene could pass either to its offspring, not a mix of the two.
• DNA Identified as Genetic Material: Later discoveries identified DNA as the carrier of genetic information, solidifying the molecular basis of heredity. Eg: Avery, MacLeod, and McCarty’s experiments in 1944 showed that DNA—not proteins—was responsible for heredity.
• Mutation Explained Heritable Variation: The understanding that mutations in DNA cause changes in traits clarified how new heritable variations arise. Eg: Mutations in the hemoglobin gene lead to sickle cell anemia, a heritable disorder.
• Disproved Lamarckian Inheritance: These findings rejected the idea that characteristics acquired during life could be inherited, as proposed by Lamarck. Eg: A bodybuilder’s muscular physique isn’t passed to their children genetically.

Why is the Cell study on cold-tolerant rice significant?

• Proof of Heritable Epigenetic Change Induced by Environment: The study demonstrated that cold exposure triggered an epigenetic modification (methylation) in rice plants, which was inherited for five generations. Eg: Rice plants exposed to cold passed on improved cold tolerance without any DNA sequence change.
• Reinforced the Role of Epigenetics in Evolution: It showed that gene expression can be regulated by epigenetic marks rather than genetic mutations, suggesting Lamarck’s idea of environmental inheritance has merit. Eg: The ACT1 gene stayed active in cold-tolerant rice due to the absence of a methylation tag, helping them survive cold stress.
• New Direction for Crop Improvement and Climate Resilience: The findings open doors for non-genetic crop adaptation methods to deal with climate change. Eg: Epigenetically trained rice varieties could be developed to withstand colder environments, improving food security.

Way forward:

• Incorporate Epigenetic Breeding in National Crop Improvement Programs: Government research bodies and agricultural universities should integrate epigenetic trait selection and editing into mainstream breeding to develop climate-resilient varieties, especially for stress-prone regions.
• Strengthen Investment in Multi-Generational Stress Trials: Increase funding for long-term, controlled environment trials to identify and stabilize heritable epigenetic traitsacross major crops, ensuring sustainable food security under climate change.

Mains PYQ:

[UPSC 2019] How can biotechnology improve the living standards of farmers?

Linkage: The core of the article reveals a novel mechanism for plant adaptation—epigenetic inheritance of cold tolerance in rice plants. This scientific breakthrough, falling under the broad umbrella of biotechnology, demonstrates a potential pathway to develop crops that can adapt to challenging environmental conditions (like cold stress) more rapidly than through traditional breeding or genetic modification.

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