Weismann Barrier
August Weismann, late 19th century · The Germ-Plasm: A Theory of Heredity (1892) (1892)
The principle that hereditary information flows only from germ cells to somatic cells, and that changes in somatic cells are not inherited.
Core Concepts
The Problem
How are acquired traits prevented from being passed to offspring if all cells share the same DNA?
The Claim
Only germ cells (sperm and egg) transmit genetic information; somatic cells are dead-end carriers of the organism's form but not of heredity.
Key Evidence
- •Weismann's mouse tail-cutting experiments showing no inherited effect.
- •Developmental biology showing early segregation of primordial germ cells.
- •Epigenetic reprogramming studies in embryos that erase most acquired marks.
Practical Implication
Under normal conditions, an organism's experiences, injuries, or learned behaviors do not alter the genetic inheritance of its offspring.
Nuance & Limits
Recent research reveals the barrier is not completely impermeable; some epigenetic marks and small RNAs can occasionally bypass reprogramming, allowing a form of transgenerational epigenetic inheritance.
Source Material
Citation Density
Foundational concept in biology textbooks; extensively cited.
Discuss Further
Open this concept in an AI assistant for deeper discussion, critique, or exploration.