DNA education

  Scanning Electron Microscopy (SEM)– Principle and Applications in Detail I. Introduction to SEM Scanning Electron Microscopy (SEM) is a type of electron microscope that uses a focused beam of high-energy electrons to generate a variety of signals at the surface of solid specimens. These signals are used to obtain information about the sample’s surface topography, composition, and other properties such as electrical conductivity. Unlike light microscopes that use visible light, SEM uses electrons , which have a much shorter wavelength, allowing higher magnification and greater resolution . II. Principle of SEM 1. Electron Beam Generation At the heart of SEM is an electron gun , which emits a beam of electrons. This is typically: A thermionic gun (e.g., tungsten filament or LaB₆ crystal). Or a field emission gun (FEG), which provides a narrower, more coherent beam. Electrons are accelerated by a high voltage (typically 1–30 kV) and directed down th...

Plant Hormones (Phytohormones) Plant hormones are small, organic molecules produced in low concentrations that regulate plant growth, development, and responses to stimuli. They act at sites often distant from their synthesis and coordinate processes like cell division, elongation, senescence, and tropic responses. Classification of Plant Hormones Plant hormones are classified into five major classical groups , along with some newly discovered growth regulators : 1. Auxins 2. Gibberellins (GAs) 3. Cytokinins 4. Abscisic Acid (ABA) 5. Ethylene New/Other growth regulators: Brassinosteroids Jasmonates (JAs) Salicylic acid (SA) Strigolactones Polyamines Nitric oxide (NO) 1. Auxins Structure and Natural Forms: Most common natural auxin: Indole-3-acetic acid (IAA) Synthesized mainly in shoot apices , young leaves , and developing seeds Biosynthesis: Derived from Tryptophan Main pathways: Indole-3-pyruvic acid (IPA) and Tryptamine pathway Tr...

The C₃ Cycle (Calvin Cycle): Mechanism, Regulation, and Importance Photosynthesis is the fundamental biological process by which plants, algae, and some bacteria convert light energy into chemical energy. This process not only sustains plant life but also supports life on Earth by producing oxygen and food. One of the central components of photosynthesis is the C₃ cycle , also known as the Calvin Cycle , which is responsible for fixing atmospheric carbon dioxide (CO₂) into organic molecules. The cycle was discovered by Melvin Calvin , Andrew Benson , and James Bassham in the 1950s using radioactive carbon (¹⁴C) tracing, for which Melvin Calvin was awarded the Nobel Prize in Chemistry in 1961 . The C₃ cycle is the most common carbon fixation pathway in plants and is called "C₃" because the first stable compound formed is a three-carbon molecule , 3-phosphoglyceric acid (3-PGA) . This cycle occurs in the stroma of chloroplasts and is light-independent , although it relies...

Glycolysis: A Detailed Exploration of Steps, Enzymes, and Inhibitors Glycolysis is one of the central metabolic pathways in living organisms. It plays a crucial role in energy production and serves as a precursor to several biosynthetic pathways. It is a ten-step enzymatic process that occurs in the cytoplasm of all living cells. The pathway involves the breakdown of one glucose molecule (6-carbon compound) into two molecules of pyruvate (3-carbon compound) , yielding energy in the form of ATP and reducing equivalents in the form of NADH . The name "glycolysis" derives from Greek: glyco (sugar) and lysis (splitting). The pathway is anaerobic , meaning it does not require oxygen, and it is fundamental for cells that rely solely on glycolysis for ATP production, such as red blood cells . Phases of Glycolysis Glycolysis can be divided into two major phases : Preparatory Phase (Energy Investment Phase): Steps 1–5 Utilizes 2 ATP molecules. Converts glucose into...

Polymerase Chain Reaction (PCR) and Its Types The Polymerase Chain Reaction (PCR) is a groundbreaking molecular biology technique that has revolutionized biological and biomedical research. Invented by Kary Mullis in 1983 , PCR allows for the in vitro amplification of specific DNA sequences , making billions of copies from even a trace amount of DNA. It is widely used in diagnostics, forensics, genetic research, agriculture, and environmental studies. Over the years, several modified types of PCR have evolved to enhance specificity, sensitivity, and applicability. Principle of PCR The principle of PCR is based on the natural replication of DNA , but it is conducted artificially in a thermal cycler . It involves: Denaturation – Unwinding and separation of double-stranded DNA by heating. Annealing – Binding of short, sequence-specific primers to the single-stranded DNA. Extension – DNA polymerase synthesizes a new strand from each primer. This cycle is repeated multip...

Qualitative and Quantitative Gel Electrophoresis Gel electrophoresis is a powerful analytical tool used widely in molecular biology , genetics , biochemistry , and biotechnology . It is based on the principle that charged molecules migrate in an electric field through a gel matrix, allowing researchers to separate , identify , and quantify biomolecules such as DNA , RNA , and proteins . There are two primary applications of gel electrophoresis: Qualitative analysis – to determine the presence, size, and purity of biomolecules. Quantitative analysis – to estimate the amount or concentration of biomolecules present in a sample. Principle of Gel Electrophoresis The technique relies on the fact that nucleic acids (DNA/RNA) are negatively charged due to their phosphate backbone. Under an electric field , they migrate toward the positive electrode (anode) through a porous gel. Proteins , depending on their net charge (determined by pH and their isoelectric point), also mov...

DNA (Deoxyribonucleic Acid): The Blueprint of Life DNA , or Deoxyribonucleic Acid , is the most fundamental molecule of life. It is present in almost all living organisms and carries the genetic instructions required for the development, functioning, reproduction, and evolution of organisms. From the smallest bacteria to the largest mammals, DNA is the code that makes life possible . This article explores the complete structure, function, history, replication, and applications of DNA. What is DNA? DNA is a nucleic acid made up of repeating units called nucleotides . Each nucleotide consists of three components: A nitrogenous base A five-carbon sugar (deoxyribose) A phosphate group There are four types of nitrogenous bases in DNA: Adenine (A) Thymine (T) Guanine (G) Cytosine (C) The structure of DNA was first accurately described by James Watson and Francis Crick in 1953, based on X-ray diffraction data produced by Rosalind Franklin and Maurice Wilkins...