1
Tracing Genetic Material: The Reign and Questioning of the Early Protein Theory
BIOL1002C-PEP-CNLesson 3
00:00

Imagine a thickBook of Life. In the early 20th century, Morgan's experiments on fruit flies found the "pages" for us β€” he demonstrated that genes are arranged linearly on chromosomes. Yet, for half a century, the scientific community was misled about what "ink" these words were written in.

ChromosomeProtein(20 amino acids)DNA(4 deoxyribonucleotides)"A Complex Anthology""A Simple Telegram?"Early View: Because proteins are more complex in structure, they were believed to be the genetic material

The Complexity Paradox: Why Was DNA Underestimated?

At the time, it was believed that life's diversity must be carried by equally complex substances. Proteins are made of20 amino acids, with nearly infinite combinations; while DNA consists of only4 bases. Under this logic, DNA was mistakenly regarded as merely an "inert scaffold" maintaining chromosomal structure.

A Shift in Logic

However, the precise continuity of life across generations hinted at another possibility: genetic material must possess highstabilityandaccurate replication capability. The halving of chromosome numbers in meiosis and their restoration through fertilization β€” this highly ordered physical process ultimately steered scientists away from complex proteins toward the seemingly "simple" DNA.

Professor's Note
In the process of forming mature germ cells from primordial germ cells, chromosomes replicate only once while the cell divides twice, halving the chromosome number. It is this precise mechanism, combined with Morgan's proof of the linear arrangement of genes, that pointed us in the direction of finding the essence of heredity.