Discovery of cells
The journey and history of biology begins with the discovery of the cell, a fundamental unit of life. The first cells are reported by Robert Hooke in the 17th century. He invent a microscope and he was curious how the the cork looks like. He interestingly observed the cork consisting of many grids of small cells. The discovery is reported by the cell wall of plant cells and the plant cell shape is like grids. His findings marked the dawn of cellular biology, understanding that all living organisms are composed of cells.
Next several years, Antonie van Leeuwenhoek, he used advanced microscope and observed living cells for the first time. He described microorganisms like bacteria and protists, calling them “animalcules. After him, from 1838 to 1839, Matthias Schleiden (a botanist) and Theodor Schwann (a zoologist) proposed the first two tenets of cell theory: All living organisms are composed of one or more cells. The cell is the basic unit of structure and function in living organisms, as we know.
The science goes very fast after it. Around 1855, Rudolf Virchow added the third tenet:
all cells arise from pre-existing cells (“Omnis cellula e cellula”). Around 1860s, improved microscopes allowed scientists to study cell organelles, such as the nucleus. Late 1800s, the biologists identified key components like the plasma membrane, cytoplasm, and early versions of what we now call the mitochondria and chloroplasts. The discovery of chromosomes and genes highlighted the role of cells in heredity. Scientists understood cellular respiration and photosynthesis, clarifying how cells generate and store energy.
The discovery of heredity in cells
The cell heredity become famous by Gregor Mendel. He explained the fundamental principles of inheritance while presenting the results of his pea plant crossbreeding experiments. He discovered the dominant/recessive Gene.
- Dominant Gene: A dominant gene is one that expresses its trait even if only one copy is present. For example, if a person inherits one dominant gene for brown eyes (B) and one recessive gene for blue eyes (b), the dominant brown eye trait will appear. Dominant traits mask the effect of recessive traits.
- Recessive Gene: A recessive gene only expresses its trait if both copies are present (one from each parent). For instance, to have blue eyes, a person must inherit two recessive genes (bb). If a dominant gene is present, the recessive trait will remain hidden.
Mendel’s laws have become such a renowned theory that they are still used in numerous textbooks today.
Despite Mendel’s great discoveries in genetics, he did not fully understand why and how inheritance occurs. He also did not fully understand the existence of mutations. The scientists continued to explore and strive to understand the role of cells. Then, a groundbreaking discovery was made: the discovery of DNA by Watson and Crick.
The following information about Watson and Crick will continue in the next story.