Biotechnology

Concept: Polymerase Chain Reaction (PCR) is a molecular biology technique used to amplify a specific segment of DNA. It allows scientists to produce millions of copies of a particular DNA sequence in a short period of time. PCR is widely used in:

• Genetic research
• Disease diagnosis
• Forensic science
• DNA fingerprinting

The PCR process consists of a repeating cycle of three main steps that occur at different temperatures. These steps are Denaturation, Annealing, and Extension.
Step 1: Denaturation} During denaturation, the double-stranded DNA is heated to about – . At this high temperature, the hydrogen bonds between the complementary DNA strands break, causing the DNA to separate into two single strands.
Step 2: Annealing} In this step, the temperature is lowered to about – . Short DNA sequences called primers bind (anneal) to their complementary sequences on the single-stranded DNA templates. These primers provide a starting point for DNA synthesis.
Step 3: Extension (Elongation)} During extension, the temperature is raised to about . At this temperature, the enzyme Taq DNA polymerase adds nucleotides to the primers and synthesizes a new complementary DNA strand. This results in the formation of new double-stranded DNA molecules.
Step 4: Correct order of PCR steps} The PCR cycle always follows this sequence: This cycle is repeated many times (usually 25–35 cycles) to amplify the target DNA.
Step 5: Evaluating the options}

• Annealing Denaturation Extension – Incorrect sequence
• Denaturation Annealing Extension – Correct sequence
• Extension Denaturation Annealing – Incorrect
• Denaturation Extension Annealing – Incorrect

Thus, the correct sequence is:

Concept: Antonie van Leeuwenhoek is widely regarded as the Father of Microbiology. He was a Dutch scientist who made significant contributions to the development of microbiology by being the first person to observe and describe microorganisms using a microscope. During the 17th century, Leeuwenhoek developed powerful single-lens microscopes that were capable of magnifying objects up to about 200–300 times. Using these microscopes, he observed tiny living organisms in water, which he called “animalcules.” These observations marked the first scientific discovery of microorganisms such as bacteria and protozoa.
Step 1: Understanding Leeuwenhoek's contribution.
Antonie van Leeuwenhoek made several groundbreaking discoveries:

• First to observe bacteria
• First to observe protozoa
• Studied microorganisms present in pond water, saliva, and other biological materials

His discoveries opened the field of microbiology, which studies microscopic organisms.
Step 2: Importance of his work in microbiology.
Leeuwenhoek's work was important because:

• He demonstrated the existence of microscopic life.
• His observations laid the foundation for later developments in bacteriology and microbiology.
• His research inspired other scientists to explore microorganisms and their role in health and disease.

Step 3: Evaluating the options.

• Louis Pasteur: Known for germ theory and pasteurization.
• Robert Koch: Known for Koch's postulates and identification of disease-causing bacteria.
• Antonie van Leeuwenhoek: First to observe microorganisms; known as the Father of Microbiology. (Correct)
• Alexander Fleming: Discovered penicillin.

Therefore, the correct answer is: