Understanding Chromatin: Walther Flemming's Contribution

The question asks about the specific year when the scientist Walther Flemming introduced the term 'chromatin'. This term is fundamental in biology, referring to the material found within the nucleus of eukaryotic cells that condenses to form chromosomes during cell division.

Who was Walther Flemming?

Walther Flemming was a pioneering German biologist and the founder of cytogenetics. His significant work involved staining techniques to observe the structures within the cell nucleus, particularly during cell division (mitosis). His observations were crucial in understanding the process by which genetic material is divided between daughter cells.

The Coining of 'Chromatin'

Flemming observed that certain substances within the nucleus stained intensely with basic dyes. Because of this affinity for staining (Greek 'chroma' meaning colour), he coined the term 'chromatin' to describe this stained substance. His detailed studies of these structures during cell division led to foundational discoveries about chromosomes.

Based on historical records of Flemming's work and publications:

• Walther Flemming first coined the term 'chromatin' in the year 1879.
• He described the process of mitosis in detail in his book "Zellsubstanz, Kern und Zelltheilung" (Cell substance, nucleus and cell division), published in 1882, building upon his earlier observations including the concept of chromatin.

Analyzing the Options

Let's look at the provided options:

• 1900: This year is too late, as Flemming had already published his extensive work on mitosis and chromatin by then.
• 1879: This is the correct year when Flemming introduced the term 'chromatin' based on his observations of stained nuclear material.
• 1849: This year is too early; Flemming's significant work on cytology began later.
• 1840: This year is also too early for Flemming's key cytological discoveries.

Therefore, the year Walther Flemming coined the term 'chromatin' is 1879.

Conclusion

Walther Flemming's coinage of the term 'chromatin' in 1879 was a crucial step in the study of cell biology and genetics. His work laid the groundwork for understanding how genetic material is organized and transmitted during cell division.

Revision Table: Key Cytology Dates

Additional Information: Chromatin and Chromosomes

It is helpful to understand the difference between chromatin and chromosomes:

• Chromatin: This is the complex of DNA and proteins (primarily histones) that forms chromosomes within the nucleus of eukaryotic cells. In interphase (when the cell is not dividing), chromatin exists as a decondensed, filamentous structure, making the genetic material accessible for transcription and replication.
• Chromosomes: These are condensed structures formed from chromatin during cell division (mitosis and meiosis). The DNA is tightly coiled and packaged within chromosomes, making them visible under a light microscope and allowing for efficient segregation during cell division. While Flemming described the process, the term 'chromosome' itself was coined later by Heinrich Wilhelm Gottfried Waldeyer in 1888.

Flemming's observation of the 'chromatin' provided the physical basis for understanding the carriers of genetic information, which were later identified as chromosomes.