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Radiation therapy is a treatment method that works by using  ionizing radiation to damage or destroy unwanted cells in the body.  This therapy is most commonly used to control or eliminate abnormal cell growth. The core idea behind radiation therapy is to deliver energy into the tissues in such a way that it damages the DNA inside the cells. Once the DNA is damaged beyond repair, the cells lose their ability to divide and eventually die. The working of radiation therapy is not based on general heating or burning of tissue. Instead, it is based on precise physical and biological effects caused by high-energy radiation. The therapy uses highly focused radiation so that diseased or fast-dividing cells are affected more than normal cells. To clearly understand how radiation therapy works, we need to study it in six main steps or components, which are: Type of radiation used (ionizing radiation) Mechanism of DNA damage (direct and indirect) Cellular response to DNA damage Radiation...

In normal human cells, there are 46 chromosomes, arranged in 23 pairs. Out of these, 22 pairs are autosomes (non-sex chromosomes) and 1 pair is sex chromosomes (XX in females and XY in males). A monosomy means that  one chromosome from a pair is missing,  so only one copy is present instead of two. When this happens to a sex chromosome, sometimes the individual can survive (like in Turner syndrome where one X chromosome is missing). But when this happens to an  autosome, it is called autosomal monosomy  and this condition is almost  always fatal.  Such embryos usually do not survive and result in early miscarriage, which is why autosomal monosomies are not seen in live-born individuals. There are the following main reasons why autosomal monosomies are not recovered in live births: 1. Severe gene dosage imbalance Each autosome contains many essential genes. Normally, both copies of each gene help maintain a balance in the amount of proteins and enzymes made ...

Non-disjunction is a type of chromosomal segregation error that occurs during cell division, particularly  meiosis,  when homologous chromosomes or sister chromatids fail to separate properly. This leads to gametes with abnormal numbers of chromosomes. In humans, non-disjunction during female meiosis is the main cause of  aneuploidy,  including conditions like Down syndrome (Trisomy 21), Turner syndrome (Monosomy X), and Klinefelter syndrome (XXY). Many studies have shown that the risk of non-disjunction increases with maternal age, especially after the  age of 35.  This is considered one of the most important biological factors in age-related decline in female fertility and increase in chromosomal abnormalities in offspring. There are four major reasons that explain why this risk increases with age in women: Prolonged meiotic arrest of oocytes Age-related loss of cohesion proteins Weakening of the spindle assembly checkpoint Age-related cellular and enviro...

The principle of spectral karyotyping (SKY) is based on  fluorescence in situ hybridization (FISH)  using  chromosome-specific DNA probes,  each labeled with a unique combination of fluorochromes. Although  only five different  fluorescent dyes are used, they are mixed in specific ratios so that each chromosome gets a unique combination of colors. This creates a specific spectral signature for every chromosome. These labeled probes are hybridized to metaphase chromosomes fixed on a glass slide. After hybridization, a fluorescence microscope with a spectral imaging system is used to detect the signals. The spectral imaging system captures the wavelength emission pattern from each chromosome. Then, spectral unmixing algorithms are applied through a computer system to separate and identify the unique color of each chromosome. In short, principle of spectral karyotyping works on the idea that: Each chromosome is labeled with a unique color code using combinatio...

The  prophase chromosome  shows a greater number of bands as compared to the metaphase chromosome. When chromosomes are stained using banding techniques like G-banding (Giemsa banding), we observe alternating light and dark regions on chromosomes. These bands are very helpful in studying the structure of chromosomes and in identifying chromosomal abnormalities. In the  prophase stage  of mitosis, the chromosomes begin to condense, but they are still in a relatively loose or extended form. Due to this less compact structure, the staining can reveal more bands with higher resolution. Therefore, prophase chromosomes show a greater number of distinct bands. In comparison,  metaphase chromosomes  are more tightly packed and highly condensed. This makes the individual bands merge together or become less visible. As a result, the number of visible bands in metaphase is lower than in prophase. So, the answer is that prophase chromosomes show more bands than metapha...

Atoms are the basic units of matter and are made up of smaller components called subatomic particles. There are many types of subatomic particles known to science, but in the context of basic atomic structure, only three are considered most important: electrons, protons and neutrons. These three particles differ in their location, charge and mass. Together, electrons, protons and neutrons form the complete structure of atoms. Their arrangement and interaction define the atom's properties, chemical behavior, and participation in physical and chemical processes. These subatomic particles laid the foundation of modern atomic theory and quantum chemistry. 1. Electron Electrons are negatively charged subatomic particles. They are extremely small in mass and are found outside the nucleus of the atom in specific regions called orbitals or shells. The charge of an electron is −1  and its mass is approximately 1/1836 of a proton or neutron, which is around 9.1 × 10⁻³¹ kg, meaning it is n...

Electromagnetic radiation is a form of energy that travels through space in the form of waves created by the motion of electrically charged particles. When such a charged particle accelerates, meaning its speed or direction changes, it gives rise to oscillating electric and magnetic fields. These two fields are always perpendicular to each other and also to the direction in which the radiation travels. This kind of energy does not need any material medium to move. It can travel through empty space (vacuum) as well as through transparent substances like air, glass or water. The theory of electromagnetic radiation was first proposed by the Scottish physicist James Clerk Maxwell in the year 1865. According to his theory, electromagnetic radiation is produced by the simultaneous propagation of electric and magnetic fields. These fields move together as waves and carry energy from one place to another. This combined wave is called an electromagnetic wave  and it is the basic form i...

A chemical element is a pure substance made up of only one type of atom, which is defined by its atomic number, i.e., the number of protons in the nucleus of each atom. This atomic number gives the element its identity and distinguishes it from all other elements. For example, carbon always has six protons, so its atomic number is 6. All substances found in nature, whether living or non-living, are made up of chemical elements or their compounds. These elements serve as the building blocks of all matter. For example, water is made from hydrogen and oxygen, rocks are made from silicon, oxygen, aluminum, etc., and living organisms are made mostly from carbon, hydrogen, oxygen, and nitrogen. So far, 118 chemical elements have been discovered, out of which 94 occur naturally. The remaining are artificially synthesized in laboratories. Among these, 80 elements have stable isotopes. All elements with atomic numbers 1 to 82 have at least one stable isotope, except technetium (43) an...

The human body is made up of various chemical elements that work together to support life. These elements are not just part of the body's physical structure like bones, muscles and skin but also control important functions such as breathing, digestion, nerve signaling and cell repair. Most of these elements combine to form molecules like water, proteins, fats, carbohydrates and nucleic acids which are the foundation of life. Although more than 60 elements are present in the body, only some of them are truly essential for survival and good health. These essential elements are grouped into three categories based on how much of them is present in the body: major elements, minor elements and trace elements. Each element, whether present in large or tiny amounts, has a special role in maintaining the structure and working of the human body. 1. Major Elements (Bulk Elements) There are six major elements that form about 98% of the total body mass. These elements are oxygen, carbon, hydrog...

The Earth's atmosphere is a layer of gases that surrounds the planet and is held in place by gravity. This gaseous envelope plays a vital role in supporting life by providing oxygen for respiration, carbon dioxide for photosynthesis and protection from harmful solar radiation. It also regulates temperature, helps in weather formation and maintains pressure balance necessary for survival. The atmosphere is composed of a mixture of different elements and compounds, each present in specific proportions. Some of these gases are present in large quantities while others occur in very small traces. However, even those present in minute amounts can have significant environmental or biological roles. The composition of the atmosphere is generally stable up to around 80 to 100 kilometers from the Earth's surface and this region is known as the homosphere where gases are well mixed. The major components of this layer are nitrogen, oxygen and argon, while several other gases like carbon d...

The ocean water of Earth is not made up of just pure water but is a complex mixture of various chemical elements. These elements exist either as part of water molecules or as dissolved ions and gases. The majority of ocean water is composed of oxygen and hydrogen, which form the water molecule (H₂O), but in addition to these, several other elements are present in small to trace amounts. These elements come from various natural sources like river runoffs, volcanic eruptions, seafloor weathering and atmospheric deposition. Some of them like sodium, chloride, and magnesium contribute to the salinity of seawater, while others like carbon, sulfur, and calcium play important roles in oceanic biological and chemical cycles. The elemental composition of ocean water by mass gives a clear idea about which elements dominate in the ocean and which are present in minor or trace amounts but still remain essential for marine life and geochemical balance. 1. Major Elements (more than 1% by mass) Th...

The Earth's crust is the thin, outermost solid layer of our planet which forms both the continents and the ocean floors. It lies above the mantle and makes up less than 1% of Earth's total volume but it is the most accessible and studied layer because all landforms, soils and rocks we see are part of the crust. The crust is composed mainly of solid rocks and minerals, which in turn are made from various chemical elements. These elements do not exist in pure form but are combined in complex compounds like silicates, oxides, carbonates etc. Although more than 90 naturally occurring elements are found in the crust, only a small group of them dominate its total mass. The composition of the crust reflects its geochemical origin, its formation history and the processes like weathering, erosion, and plate tectonics that continuously shape it. Each of these elements has specific roles in rock formation and Earth’s surface structure. Their proportions are usually expressed by mass pe...

Biomolecules are natural chemical compounds that are found inside all living organisms. These molecules are essential for life. They form the structure of cells and carry out various biological functions such as producing energy, building tissues, storing information and regulating reactions. Without biomolecules, life cannot exist. Biomolecules are mostly organic, which means they are made of carbon atoms along with hydrogen, oxygen, nitrogen, phosphorus and sulfur. These elements combine in different ways to form molecules that help the cell survive, grow and reproduce. All organisms, from the smallest bacteria to large animals and plants, are made of biomolecules. The chemical structure of biomolecules is mostly the same in all living organisms. For example, glucose found in humans and in plants is exactly the same molecule. This shows that biomolecules are universal in nature and conserved through evolution. Major Types of Biomolecules Biomolecules are mainly divided into f...

Birds have a fascinating adaptation that allows them to sleep securely on branches without falling off. This is due to a special perching reflex or tendon locking mechanis in their legs known as the flexor tendon. When a bird lands on a branch and bends its legs, this tendon automatically tightens, causing the toes to curl around the branch and grip it firmly. This action does not need any active muscle contraction and works just like a lock. Once the toes are locked in place, they stay that way as long as the leg remains bent. This is an involuntary process, which means that the bird does not need to consciously control it. The body weight of the bird naturally keeps the legs bent, which keeps the locking mechanism engaged. Therefore, even when the bird is in deep sleep, the grip remains strong and the bird does not fall. The toes will unlock only when the bird straightens its legs consciously, which usually happens when it wakes up or prepares to fly. This adaptation is especially...