MUKHLiS TANVEER JAN KURD

Tanveer Kurd. Biology

Acid

An acid is a type of chemical substance that, when dissolved in water or another aqueous solution, donates protons (hydrogen ions, H+) or accepts pairs of electrons. Acids are known for their characteristic sour taste, ability to turn certain indicators red, and their capacity to react with bases to form salts and water in a chemical process called neutralization.

Acids are classified based on their behavior and properties:

Strong Acids: These acids completely dissociate in water, releasing a high concentration of hydrogen ions. Examples include hydrochloric acid (HCl), sulfuric acid (H2SO4), and nitric acid (HNO3).

Weak Acids: Weak acids partially dissociate in water, releasing fewer hydrogen ions. Examples include acetic acid (found in vinegar), citric acid (found in citrus fruits), and carbonic acid (formed when carbon dioxide dissolves in water).

Acids play crucial roles in various chemical and biological processes:

Acid-Base Reactions: Acids react with bases to form salts and water in a neutralization reaction. The concentration of hydrogen ions (H+) in a solution determines its pH value, which is a measure of its acidity or alkalinity (basicity).

Digestion: In the stomach, gastric acid (mainly hydrochloric acid) helps break down food and kill bacteria, aiding in the digestive process.

Industrial Processes: Acids are used in various industries for processes like metal cleaning, pH regulation, and production of various chemicals.

Chemical Synthesis: Acids are used as catalysts or reactants in chemical reactions to produce desired compounds.

It's important to note that while many people associate the term "acid" with something harmful or corrosive, not all acids are dangerous. In fact, many acids are naturally occurring and essential for various biological processes. However, strong acids can indeed be corrosive and harmful to living tissues.

In summary, an acid is a chemical substance that donates protons or accepts electrons, leading to characteristic acidic properties and reactions. They are important in chemistry, biology, and various industrial applications.

Acid hydrolases

Acid hydrolases are a group of enzymes that function within cells to break down complex molecules through a process called hydrolysis. Hydrolysis involves the addition of water molecules to the bonds of larger molecules, causing them to split into smaller components. Acid hydrolases specifically operate in acidic environments within cellular compartments called lysosomes.

Lysosomes are membrane-bound organelles containing a variety of enzymes, including acid hydrolases. These enzymes play a critical role in digesting and recycling cellular waste materials, as well as breaking down molecules such as proteins, lipids, nucleic acids, and complex carbohydrates.

The acidic environment within lysosomes is maintained by proton pumps in the lysosomal membrane, which actively transport hydrogen ions (protons) into the lysosome. This acidic pH is essential for the optimal functioning of acid hydrolases, as it provides the appropriate conditions for their enzymatic activities.

Different types of acid hydrolases are responsible for breaking down specific types of molecules:

Proteases: These enzymes break down proteins into smaller peptides and amino acids. They help recycle damaged or no longer needed proteins within the cell.

Lipases: Lipases break down lipids (fats) into fatty acids and glycerol, which can then be used for energy production or other cellular processes.

Nucleases: Nucleases are responsible for breaking down nucleic acids, such as DNA and RNA, into their individual nucleotide components.

Glycosidases: These enzymes break down complex carbohydrates (glycans) into simpler sugars (monosaccharides).

The proper functioning of acid hydrolases and lysosomes is essential for maintaining cellular health and homeostasis. Any dysfunction in these enzymes or lysosomal processes can lead to a group of disorders known as lysosomal storage diseases, where various molecules accumulate within cells due to inadequate breakdown and recycling.

In summary, acid hydrolases are enzymes found in lysosomes that function in an acidic environment to break down complex molecules through hydrolysis. They play a vital role in cellular waste disposal, recycling, and maintaining overall cellular function.

Absorption Spectrum

An absorption spectrum is a graphical representation or a plot that illustrates the amount of light absorbed by a substance at various wavelengths or frequencies. This spectrum is particularly useful in fields such as physics, chemistry, and biology to understand the interactions between light and matter.

When light passes through a substance, certain wavelengths of light are absorbed by the molecules within that substance. The remaining wavelengths are transmitted or reflected. The absorption spectrum shows which wavelengths are absorbed and to what extent. Different molecules and compounds have unique absorption spectra, which can provide valuable information about their composition and properties.

For instance, in the context of spectroscopy, scientists use absorption spectra to identify and analyze various substances. By comparing the absorption spectrum of an unknown substance with the absorption spectra of known substances, scientists can determine its composition. This technique is widely used in fields like astronomy, where absorption lines in the spectra of stars and galaxies provide insights into their chemical compositions and physical conditions.

In summary, an absorption spectrum is a visual representation of how light is absorbed by a substance across different wavelengths, aiding in the identification and analysis of various materials and molecules.

Action-Binding Protein

Actin-binding proteins are a diverse group of proteins that interact with actin filaments within cells. These proteins play a crucial role in regulating the structure, dynamics, and functions of the actin cytoskeleton. By binding to actin filaments, actin-binding proteins modulate processes such as cell movement, shape maintenance, signaling, and intracellular transport.

Key points about actin-binding proteins include:

Regulation of Actin Filament Dynamics: Actin-binding proteins can either stabilize or destabilize actin filaments, influencing their polymerization and depolymerization rates. This dynamic behavior is essential for processes like cell migration and the formation of cellular structures.

Cell Motility: Actin-binding proteins are integral to cell motility. They help organize actin filaments in specific arrangements, such as lamellipodia and filopodia, which are essential for cell crawling and movement. Examples of actin-binding proteins involved in motility include Arp2/3 complex, cofilin, and profilin.

Muscle Contraction: In muscle cells, actin-binding proteins are vital for proper muscle contraction. Troponin and tropomyosin, for example, regulate the interaction between actin and myosin during muscle contraction.

Cell Adhesion and Shape: Actin-binding proteins contribute to the formation of cellular structures like focal adhesions, which mediate cell attachment to the extracellular matrix. They also play a role in maintaining cell shape and stability.

Endocytosis and Vesicle Transport: Actin-binding proteins are involved in processes like endocytosis, where cells engulf materials from the outside. They also aid in intracellular vesicle transport by interacting with molecular motors.

Signaling Pathways: Some actin-binding proteins are involved in signaling pathways. For instance, proteins like filamin and α-actinin can link actin filaments to membrane receptors, enabling the transmission of signals from the cell surface to the actin cytoskeleton.

Crosslinking and Bundling: Actin-binding proteins can crosslink actin filaments, creating networks or bundles that contribute to cell shape and structural stability. Examples include fimbrin and spectrin.

Disease Implications: Dysregulation of actin-binding proteins can lead to various diseases. For example, defects in actin-binding proteins are associated with conditions like muscular dystrophies and metastatic cancer progression.

Overall, actin-binding proteins are essential for orchestrating the intricate activities of the actin cytoskeleton. Their interactions with actin filaments enable cells to perform a wide array of functions, from cell movement to division, and they are central to maintaining the structural integrity and functional versatility of cells.

Action

Actin is a protein that plays a fundamental role in various cellular processes, particularly in cell structure, movement, and muscle contraction. It is a major component of the cytoskeleton, which is the dynamic framework of proteins within cells that provides structural support, shape, and helps with cellular movement and division.

Key points about actin include:

Structure: Actin is a globular protein that can polymerize (join together) to form long, thin filaments. These filaments can further assemble into larger structures, such as microfilaments or actin filaments.

Cytoskeleton: Actin filaments are a vital part of the cytoskeleton, a network of protein filaments that give the cell its shape and help it maintain its structural integrity. The cytoskeleton is also involved in various cellular processes like cell migration, endocytosis (cellular uptake of materials), and cell division.

Cell Movement: Actin is integral to cellular motility. In a process called actin-based or microfilament-based motility, actin filaments interact with motor proteins (such as myosin) to generate force and movement within the cell. This mechanism is important in processes like cell crawling, muscle contraction, and the movement of cellular structures.

Muscle Contraction: Actin is a primary component of muscle fibers. In muscle contraction, interactions between actin and myosin generate the force required for muscle movement. This process is central to bodily movements, including walking, lifting objects, and even the beating of the heart.

Cell Division: Actin plays a role in cytokinesis, the final stage of cell division where the cytoplasm is divided between the two daughter cells. Actin filaments form a contractile ring that pinches the cell's membrane, leading to separation.

Cell Adhesion: Actin filaments are involved in maintaining cell shape and adhesion to other cells and the extracellular matrix. They play a role in forming structures like focal adhesions, which are important for cell attachment and migration.

Dynamic Behavior: Actin filaments are highly dynamic, constantly forming and disassembling in response to various cellular signals. This dynamic behavior allows cells to quickly adapt to changing environments and perform their functions efficiently.

In summary, actin is a versatile and essential protein found in all eukaryotic cells, contributing to cell structure, movement, muscle contraction, cell division, and numerous other critical cellular processes. Its dynamic nature and interactions with other proteins make it a cornerstone of cell biology and a key player in the functioning of living organisms.

Action Potential

An action potential is a brief, rapid change in the electrical potential across the cell membrane of a neuron or muscle cell. It is a fundamental mechanism that allows cells to transmit electrical signals over long distances, serving as the basis for communication within the nervous system and for muscle contraction.

Key points about action potentials include:

Resting Membrane Potential: Neurons and muscle cells maintain a resting membrane potential, which is a difference in electrical charge between the inside and outside of the cell. This is maintained by the movement of ions across the cell membrane, primarily through ion channels.

Threshold: When a stimulus (such as a neurotransmitter binding to a neuron) reaches a certain level of strength, it can cause a localized depolarization of the cell membrane. If this depolarization reaches a critical level called the threshold, it triggers the initiation of an action potential.

Depolarization Phase: Once the threshold is reached, voltage-gated sodium channels in the cell membrane open. This allows sodium ions (Na+) to rapidly flow into the cell, causing a rapid depolarization of the membrane. This depolarization is the rising phase of the action potential.

Peak and Repolarization: As the action potential reaches its peak, sodium channels close, and voltage-gated potassium channels open. Potassium ions (K+) then flow out of the cell, repolarizing the membrane back to its resting potential. This repolarization is the falling phase of the action potential.

Hyperpolarization and Refractory Period: In some cases, the membrane potential may temporarily become more negative than the resting potential, resulting in a hyperpolarization. After an action potential, there is a refractory period during which the cell is less likely to generate another action potential immediately, ensuring that signals are transmitted in one direction.

Propagation: The action potential generated at one location on the cell membrane can trigger adjacent regions to reach their threshold and generate their own action potentials. This allows the signal to travel along the length of the neuron without losing strength.

All-or-None Principle: An action potential is an all-or-none event, meaning that if the threshold is reached, the action potential occurs with a consistent amplitude and duration. The strength of the stimulus does not affect the size of the action potential; it either occurs fully or not at all.

Speed and Myelination: The speed of action potential propagation can be influenced by factors such as the presence of myelin, a fatty substance that insulates some neurons. Myelinated neurons conduct action potentials faster due to saltatory conduction, where the action potential "jumps" between gaps in the myelin sheath called nodes of Ranvier.

In summary, an action potential is a rapid change in the electrical potential across the cell membrane of neurons and muscle cells, serving as the basis for nerve communication and muscle contraction. It involves a sequence of depolarization, repolarization, and, in some cases, hyperpolarization phases, allowing cells to transmit electrical signals effectively.

Action Spectrum

An action spectrum is a graphical representation that illustrates the efficiency of different wavelengths of light in driving a specific biological or chemical process. It is a fundamental concept in various fields such as photobiology, plant physiology, and biochemistry, helping to understand how different wavelengths of light affect particular reactions or functions within living organisms.

Key points about action spectra include:

Specific Processes: Action spectra are designed to highlight the wavelengths of light that are most effective in driving a specific biological or chemical process. These processes can include photosynthesis, photoreceptor activation, DNA damage, and other light-driven reactions.

Absorption by Pigments: In many cases, the action spectrum corresponds closely to the absorption spectrum of the pigments or molecules involved in the process. For example, chlorophyll molecules in plants primarily absorb light in the blue and red parts of the spectrum, aligning with the action spectrum of photosynthesis.

Variability: Different organisms or processes may have distinct action spectra due to variations in the pigments and molecules they use to capture light energy. As a result, the action spectrum for one organism or process might differ from that of another.

Quantitative Data: Action spectra provide quantitative data about the efficiency of different wavelengths in driving a process. The height of the graph's curve at each wavelength indicates how effective that wavelength is in stimulating the reaction.

Light Adaptation: Action spectra can also help researchers understand how organisms adapt to different light environments. For instance, plants might have different action spectra for different photosynthetic pigments, allowing them to capture light effectively in various conditions.

Medical Applications: Action spectra are used in medical research to understand how different wavelengths of light affect biological tissues. For example, in photodynamic therapy, researchers use action spectra to determine the wavelengths of light that are most effective in activating light-sensitive drugs for targeted cancer treatment.

Experimental Design: Scientists use action spectra to design experiments that isolate and quantify the impact of specific wavelengths on a given process. By illuminating organisms with light of varying wavelengths and measuring the resulting responses, they can construct action spectra.

In summary, an action spectrum is a graphical representation that showcases the effectiveness of different wavelengths of light in driving specific biological or chemical processes. It aids in understanding the interaction between light and living organisms, shedding light on processes ranging from photosynthesis to photoreception to medical treatments involving light-based therapies.

Activation Energy

Activation energy is a concept in chemistry that refers to the minimum amount of energy required for a chemical reaction to occur. It's the energy needed to break the bonds in the reactant molecules so that they can rearrange and form new products. In essence, activation energy is the energy barrier that must be overcome for a reaction to proceed.

Key points about activation energy include:

Reaction Energy Profile: Activation energy is often depicted in a reaction energy profile diagram. This diagram shows the energy levels of reactants, products, and the transition state—the high-energy state that molecules must reach before the reaction can occur.

Collisions and Molecules: For a reaction to happen, reactant molecules need to collide with sufficient energy and in the correct orientation. However, not all collisions lead to a reaction; only those with energy equal to or greater than the activation energy result in a successful reaction.

Catalysts: Catalysts are substances that can lower the activation energy of a reaction. They achieve this by providing an alternative reaction pathway with a lower energy barrier. This makes it easier for reactant molecules to reach the transition state and proceed to products.

Temperature and Activation Energy: Increasing the temperature typically increases the kinetic energy of molecules, which results in more frequent and energetic collisions. This can help molecules overcome the activation energy barrier and increase the rate of reaction.

Reaction Rates: Activation energy directly influences the rate at which a reaction occurs. Reactions with lower activation energies tend to happen more quickly than those with higher activation energies.

Biological Reactions: Activation energy is also relevant in biological systems. Enzymes, which are biological catalysts, lower the activation energy of reactions within cells. This enables essential biochemical processes to occur at the relatively mild temperatures found within living organisms.

Chemical Kinetics: Activation energy is a key concept in the field of chemical kinetics, which studies the rates of chemical reactions and the factors that influence them.

In summary, activation energy is the minimum energy required for a chemical reaction to happen. It serves as a barrier that reactant molecules must overcome through energetic collisions in order to proceed to the product state. Understanding activation energy is crucial for predicting reaction rates and designing processes that involve chemical transformations.

Active Site

The active site is a critical feature within an enzyme or a protein where specific biochemical reactions take place. It is a pocket or a region with a unique three-dimensional structure that facilitates the binding of substrate molecules and catalyzes chemical transformations, leading to the formation of products.

Key points about the active site include:

Substrate Binding: The active site possesses a specific shape and chemical properties that allow it to bind to a particular substrate molecule. The binding between the active site and the substrate is often highly specific, like a lock and key mechanism.

Catalysis: Once the substrate is bound to the active site, the enzyme can catalyze the reaction by facilitating the rearrangement of chemical bonds. This process lowers the activation energy required for the reaction, making it more favorable and efficient.

Induced Fit: In some cases, the active site undergoes a conformational change upon substrate binding. This phenomenon, known as the induced fit model, ensures a tighter and more precise interaction between the enzyme and substrate.

Transition State: The active site stabilizes the transition state of the reaction, which is the high-energy intermediate state that molecules must pass through during a reaction. By stabilizing the transition state, the enzyme accelerates the reaction rate.

Enzyme-Substrate Complex: The complex formed between the enzyme and substrate is referred to as the enzyme-substrate complex. This complex allows the enzyme to position the substrate molecules in a way that promotes the reaction.

Specificity: The active site's structure and chemical properties determine the enzyme's specificity for particular substrates. This specificity ensures that enzymes only catalyze reactions relevant to their biological function.

Cofactors and Coenzymes: Some enzymes require additional molecules, called cofactors or coenzymes, to assist in catalysis. These molecules can bind to the active site and participate in the reaction.

Enzyme Regulation: The active site is also a target for enzyme regulation. Modulators can influence enzyme activity by binding to the active site and altering the enzyme's ability to bind substrates or catalyze reactions.

In summary, the active site is a specific region within an enzyme or protein where substrate binding and catalysis occur. Its unique structure and chemistry play a pivotal role in facilitating biochemical reactions with precision, efficiency, and specificity.

Active transport

Active transport is a cellular process that involves the movement of substances, such as ions or molecules, across a cell membrane against their concentration gradient. This process requires the expenditure of energy, usually in the form of adenosine triphosphate (ATP), to transport molecules from an area of lower concentration to an area of higher concentration.

Key points about active transport include:

Energy Requirement: Unlike passive transport mechanisms (such as simple diffusion or facilitated diffusion), which rely on the natural movement of molecules from areas of high concentration to low concentration, active transport moves molecules against their concentration gradient. This requires energy input to overcome the natural tendency of molecules to move in the opposite direction.

Membrane Proteins: Active transport is facilitated by specific membrane proteins called pumps. These pumps are embedded in the cell membrane and use energy, typically derived from ATP hydrolysis, to actively move molecules across the membrane.

Ion Pumps: One of the most well-known examples of active transport is the sodium-potassium pump (Na+/K+ pump), which actively transports sodium ions (Na+) out of the cell and potassium ions (K+) into the cell. This pump maintains the resting membrane potential of neurons and is crucial for proper cellular function.

Proton Pump: Another important example is the proton pump, found in the membranes of organelles like mitochondria and the cell's plasma membrane. It actively transports protons (hydrogen ions, H+) to establish proton gradients, which can be used for processes like ATP synthesis.

Secondary Active Transport: Some active transport processes are coupled with passive transport mechanisms. In secondary active transport, the energy obtained from the movement of one molecule down its concentration gradient is used to drive the active transport of another molecule against its gradient.

Importance in Cellular Processes: Active transport is essential for maintaining proper ion concentrations within cells, which is crucial for processes like nerve transmission, muscle contraction, and osmotic balance. It's also involved in nutrient uptake and waste removal.

Selective Transport: Active transport pumps are often highly selective, allowing only specific ions or molecules to be transported. This selectivity is important for maintaining the integrity of cellular environments.

ATP Utilization: The hydrolysis of ATP provides the energy required for active transport. ATP donates one of its phosphate groups to the pump, enabling a conformational change that transports the target molecule across the membrane.

In summary, active transport is a cellular process that moves molecules against their concentration gradient, requiring energy input and specific membrane proteins. It's a crucial mechanism for maintaining proper ion balances, generating energy gradients, and ensuring essential cellular functions.

Adaptive immune response

The adaptive immune response is a sophisticated defense mechanism of the immune system that recognizes and targets specific pathogens or foreign substances. It develops over time in response to exposure to various antigens (molecules that trigger an immune response) and provides long-lasting protection against future infections.

Key points about the adaptive immune response include:

Specificity: Unlike the innate immune response, which provides a general defense against a wide range of pathogens, the adaptive immune response is highly specific. It targets particular antigens associated with pathogens, such as proteins on the surface of bacteria or viruses.

Immunological Memory: One of the hallmarks of the adaptive immune response is immunological memory. After exposure to an antigen, certain immune cells, primarily memory B cells and memory T cells, "remember" the antigen. If the same antigen is encountered again, the immune response is faster, more robust, and more effective in eliminating the pathogen.

Antigen Recognition: The adaptive immune response involves specialized immune cells called B cells and T cells. These cells possess antigen receptors on their surfaces that can recognize specific antigens. B cells produce antibodies, while T cells have receptors that interact with antigens presented on the surfaces of other cells.

Clonal Selection and Expansion: When a B cell or T cell encounters its specific antigen, it undergoes clonal selection. This process leads to the proliferation of identical cells, known as clones, that can recognize and target the antigen. This ensures a more potent response to the invading pathogen.

Antibody Production: B cells play a central role in antibody-mediated immunity. When a B cell encounters its target antigen, it becomes activated and differentiates into plasma cells, which produce large quantities of antibodies. Antibodies are proteins that can bind to antigens and neutralize them, marking them for destruction.

Cell-Mediated Immunity: T cells are responsible for cell-mediated immunity. Helper T cells assist other immune cells in their functions, while cytotoxic T cells directly target and destroy infected cells.

Major Histocompatibility Complex (MHC): T cells recognize antigens presented on the surfaces of cells by molecules called major histocompatibility complexes (MHC). This interaction is crucial for activating T cells and initiating an immune response.

Vaccination: The principle behind vaccination is to stimulate the adaptive immune response by exposing the body to harmless or weakened forms of pathogens or their antigens. This prepares the immune system to respond effectively if the individual is exposed to the actual pathogen in the future.

In summary, the adaptive immune response is a highly specific and targeted defense mechanism that provides immunity against pathogens through the recognition of antigens. Its ability to generate immunological memory forms the basis for long-term protection against infectious diseases and is a key concept in immunology and vaccination strategies.

Adenosine triphosphate ( ATP)

Adenosine triphosphate, often abbreviated as ATP, is a molecule that serves as the primary energy currency of cells in living organisms. It is a small, multifunctional molecule that stores and transfers energy for various cellular processes, making it a crucial component for the functioning of all living cells.

Key points about adenosine triphosphate (ATP) include:

Chemical Structure: ATP is composed of three phosphate groups (triphosphate) attached to an adenosine molecule. Adenosine consists of a nitrogenous base (adenine) and a ribose sugar.

Energy Storage: The high-energy phosphate bonds between the phosphate groups in ATP store a significant amount of energy. When these bonds are broken through a process called hydrolysis, energy is released and can be utilized by the cell for various activities.

Energy Currency: ATP is often referred to as the "energy currency" of cells because it can be easily generated and quickly used to power cellular processes. When a cell needs energy, it can rapidly break down ATP to release energy.

Cellular Processes: ATP is involved in numerous cellular activities, including muscle contraction, active transport of molecules across cell membranes, DNA synthesis, protein synthesis, and cell division.

ATP Hydrolysis: The breakdown of ATP occurs through hydrolysis, where water molecules are used to cleave the high-energy phosphate bond. This process yields adenosine diphosphate (ADP) and an inorganic phosphate (Pi), along with the release of energy.

ATP Regeneration: Cells continuously regenerate ATP to maintain adequate energy levels. This regeneration primarily occurs through cellular respiration, where nutrients like glucose are metabolized to produce ATP.

Mitochondria: Mitochondria are the powerhouse of the cell and are the primary sites of ATP production through oxidative phosphorylation, a process that involves the electron transport chain and ATP synthase.

ATP and Enzymes: Many enzymes require ATP as a cofactor to function. For instance, ATP is used in phosphorylation reactions to transfer phosphate groups to other molecules, activating or deactivating them.

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Chromosomes and DNA

Chromosomes

Discovery

Chromosomes are thread like structures that appear inside the nucleus at the time of cell division. They were first observed by the German embryologist Walther Fleming in 1882, when he was examining the rapidly dividing cells of salamander larvae. Since their discovery, chromosomes have been found in the cells of all eukaryotes.

Number of chromosomes

Their number however varies from species to species. Penicillium, a fungus, has only one pair of chromosomes, while some ferns have more than 500 pairs. A mosquito has 6, honeybee 32, corn 20, sugarcane 80, frog 26 and a mouse has 40 chromosomes. Human cells have 46 chromosomes, consisting of 23 pairs.

Importance.

Each of human 46 chromosomes contains hundreds or thousands of genes that play important roles in determining how a person’s body develops and functions.

The possession of all these chromosomes is therefore, essential for survival.

Missing of a part or whole of chromosome leads to serious consequences, usually death occurs

Structure

Typically, a chromosome is made of chromatids, centromere, (primary constriction), and a secondary constriction.

TYPES OF CHROMOSOMES

Chromosomes may widely differ in appearance. They vary in

staining properties,

the location of centromere,

the relative length of the two arms on either side of centromere, or

the position of constricted regions along the arms

Size.

Karyotype

The particular array of chromosomes that an individual possesses is called its karyotype. Karyotypes show marked differences among species and sometimes even among individuals of the same species.

Chromosomes on the basis of location of centromere.

The chromosomes are called telocentric, acrocentric, sub metacentric and metacentric depending upon the location of centromere between the middle and tip of the chromosomes

Metacentric Chromosomes

Metacentric chromosomes have the centromere in the center, such that both sections are of equal length. Human chromosome 1 and 3 are metacentric

Submetacentric Chromosomes

Submetacentric chromosomes have the centromere slightly offset from the center leading to a slight asymmetry in the length of the two sections. Human chromosomes 4 to 12 are submetacentric.

Acrocentric Chromosomes

Acrocentric chromosomes have a centromere which is near the end of chromosomes. Human chromosomes 13, 15, 21, and 22 are acrocentric.

Telocentric Chromosomes

Telocentric chromosomes have the centromere at the very end of the chromosome. Humans do not possess telocentric chromosomes but they are found in other species such as mice

Shapes.

These chromosomes acquire different shapes at the time of anaphase during cell division. The usual shapes are i, j and v.

THE CHROMOSOMAL THEORY OF INHERITANCE

Contribution of Correns.

A central role for chromosomes in heredity was first suggested in 1900 by the German geneticist Karl Correns, in one of the papers announcing the rediscovery of Mendel’s work.

Contribution of Walter Sutton

Soon after, observations that similar chromosomes paired with one another during meiosis led directly to the chromosomal theory of inheritance, first formulated by the American Walter Sutton in 1902.

Postulates of the Chromosomal Theory of Inheritanc

The factors described by Mendel are the genes which are the actual physical units of heredity.

The genes are present on chromosomes in a linear order.

It is written for educational purpose only don't use these topics for earning money.

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