Introduction of Cytology and Molecular Biology
Before exploring the advanced techniques of biotechnology and genetic engineering, it is essential to understand the basic building blocks of life. All biotechnological processes, from creating genetically modified crops to developing life-saving vaccines, operate at the microscopic level.
This foundation rests on two closely related branches of science: Cytology and Molecular Biology.
1. Cytology: The Study of the Cell
Cytology is the branch of biology dedicated to the study of the structure, function, and chemistry of cells. The cell is the fundamental, structural, and functional unit of all living organisms. To successfully manipulate living systems, scientists must first thoroughly understand how a cell operates as a self-contained factory.
Biotechnology frequently works with two main categories of cells:
- Prokaryotic Cells: These are simple, single-celled organisms that lack a true nucleus, such as bacteria. Because they multiply rapidly and are easy to manipulate, bacteria are widely used in biotechnology as “micro-factories” to produce proteins like human insulin.
- Eukaryotic Cells: These are more complex cells containing a well-defined nucleus and membrane-bound organelles. Plants, animals, and humans are made of eukaryotic cells.
2. Molecular Biology: The Molecules of Life
While cytology looks at the cell as a whole, molecular biology zooms in even further. It is the study of biological activities at the molecular level, focusing specifically on how molecules interact to sustain life.
The primary focus of molecular biology is understanding the “Central Dogma.” This is the core principle explaining the flow of genetic information within a biological system:
1) DNA (Deoxyribonucleic Acid): The permanent master blueprint that stores the genetic instructions.
2) RNA (Ribonucleic Acid): The temporary messenger that reads and carries the instructions from the DNA.
3) Proteins: The complex molecules built using the RNA’s instructions. Proteins perform almost all the structural and functional duties inside the organism.
3. The Connection to Biotechnology
Biotechnology is essentially the practical application of molecular biology and cytology. By understanding how a cell’s natural machinery reads DNA to build proteins, scientists can artificially introduce new genetic instructions into a cell. The cell will then use its natural processes to read this new DNA and produce highly specific, desired products for medicine, agriculture, and industry.
Scientific Milestones in Cell Biology
The foundations of modern biotechnology were established through scientific advances from the sixteenth to nineteenth centuries:
- In 1590, Zacharias Janssen, a Dutch lens-maker, invented the first compound microscope, magnifying up to 9×.
- In 1665, Robert Hooke coined the term cell after observing cork tissues.
- In 1676, Antonie van Leeuwenhoek observed microorganisms (termed “animalcules”) in pond water.
- The cell theory was developed in the eighteenth century by Schleiden and Schwann, who proposed that all organisms are made of cells. In 1858, Rudolf Virchow concluded that “all cells arise from pre-existing cells”, reinforcing the cell as the basic unit of life.
- Louis Pasteur further proved that spontaneous generation of life is false and introduced the method of pasteurisation. In 1896, Eduard Buchner demonstrated that yeast extracts could ferment sugars to ethyl alcohol, showing that biochemical transformations could occur without whole cells.
Chromosomes are tiny, thread-like structures found inside the nucleus of our cells. They are made of DNA and proteins, and they carry all the instructions (genes) needed for the body to grow, develop, and function. In humans, each cell has a total of 46 chromosomes, arranged in 23 pairs:
We inherit half of our chromosomes from our mother and half from our father. That means one chromosome of each pair comes from each parent.
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UPSC(2000)
Q. Assertion (A):
In human beings, the females play a major role in determining the sex of the offspring.
Reason (R): Women have two ‘X’ chromosomes.
Options:
(A) Both A and R are true, and R is the correct explanation of A
(B) Both A and R are true, but R is not a correct explanation of A
(C) A is true, but R is false
(D) A is false, but R is true
Answer: (D) A is false, but R is true
Explanation:
- Reason is true: Women indeed have two X chromosomes (XX).
- Assertion is false: The sex of a child is not determined by the female, but by the male.
o Males have one X and one Y chromosome (XY).
o The sperm may carry either an X or Y chromosome.
§ X from sperm → girl (XX)
§ Y from sperm → boy (XY)
