25. Germplasm theory was proposed by-
    (1) Dobszzhanky (2) Weismann
    (3) Meyer (4) Mendel

Introduction

The study of heredity has undergone remarkable transformations over the centuries. One of the most pivotal moments in this journey was the proposal of the germplasm theory by August Weismann. This theory fundamentally changed how scientists understand the transmission of genetic information and laid the groundwork for modern genetics.

What Is the Germplasm Theory?

The germplasm theory states that hereditary information is transmitted only by germ cells—such as sperm and egg cells—found in the gonads. Somatic cells, which make up the rest of the body, do not contribute to heredity. This means that only changes in the germ cells can be passed on to future generations, while changes acquired by somatic cells during an organism’s lifetime are not inherited.

August Weismann: The Man Behind the Theory

August Weismann (1834–1914), a German evolutionary biologist, proposed the germplasm theory in the late 19th century. He first introduced the concept in the 1880s and published his comprehensive work, Das Keimplasma: eine Theorie der Vererbung (“The Germ Plasm: a Theory of Inheritance”), in 1892.

Key Points of Weismann’s Theory

• Separation of Germ and Somatic Cells: Multicellular organisms consist of two distinct cell types: germ cells (which carry heritable information) and somatic cells (which perform bodily functions).

• One-Way Transmission: Hereditary material flows only from germ cells to somatic cells, never the reverse. This concept is known as the Weismann barrier.

• No Inheritance of Acquired Traits: Traits acquired during an organism’s lifetime (such as a cut tail in a mouse) are not passed on to offspring, directly challenging Lamarck’s theory of inheritance of acquired characteristics.

Weismann’s Famous Experiment

To demonstrate his theory, Weismann conducted an experiment in which he cut off the tails of mice for 22 successive generations. Despite this, each new generation was born with normal tails, proving that acquired characteristics in somatic cells do not affect the hereditary material in germ cells.

Impact on Genetics and Evolution

Weismann’s germplasm theory was revolutionary because it:

• Disproved the idea that acquired traits could be inherited.

• Established the concept of the continuity and immortality of germ cells.

• Provided a clear distinction between the genetic material passed to offspring and the rest of the body’s cells.

• Laid the foundation for the chromosome theory of inheritance and modern genetics.

Criticisms and Limitations

While the germplasm theory was groundbreaking, it did not account for all forms of reproduction, such as asexual reproduction in some lower organisms. However, its core principles remain central to genetics and evolutionary biology.

Conclusion

August Weismann is credited with proposing the germplasm theory, a cornerstone in the field of genetics. His work clarified the mechanisms of heredity, separating the roles of germ and somatic cells, and debunked the inheritance of acquired characteristics. Today, the germplasm theory continues to influence our understanding of genetic inheritance and evolution.

Correct answer:
(2) Weismann

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