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Semester 1: Cell Biology and Genetics
Introduction and history of Biotechnological science with special reference to contribution of Indian scholars in biological sciences
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Biotechnological science is the interdisciplinary field that involves the application of biological organisms, systems, or processes to develop or create products and technologies. It combines knowledge from biology, chemistry, physics, and engineering to manipulate living matter for useful purposes.
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The history of biotechnology can be traced back thousands of years, encompassing traditional techniques such as fermentation and selective breeding. The modern era began in the late 19th and early 20th centuries with the advent of microbiology and genetics.
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Indian scholars have made significant contributions to the field of biotechnological sciences. Notable figures include Dr. M.S. Swaminathan, who played a pivotal role in India's Green Revolution, and Dr. A.P.J. Abdul Kalam, who contributed to the development of bioinformatics and space biotechnology.
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Research and development in India have led to advancements in areas such as agricultural biotechnology, healthcare, and environmental sustainability. Indian institutions and universities are increasingly recognized for their contributions to genetic engineering, molecular biology, and biotechnology.
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The future prospects of biotechnology in India look promising with increasing investment in research and development, support from the government, and collaboration with international organizations. The potential to address global challenges such as food security, disease management, and environmental conservation is significant.
Prototype structure of animal, plant and bacterial cells, Diversity of cell size and shape, Cell theory, C-value paradox, Cell Membrane: Chemical components of biological membranes, organization and Fluid Mosaic Model, and membrane transport, Cytoskeleton and Extra cellular matrix
Prototype structure of animal cells
Animal cells are typically characterized by a membrane-bound nucleus, membrane-bound organelles, and a flexible cell membrane. Key organelles include mitochondria for energy production, ribosomes for protein synthesis, endoplasmic reticulum for transport and synthesis of molecules, and lysosomes for digestion. Shape can vary, but cells tend to be round or irregular.
Prototype structure of plant cells
Plant cells have a rigid cell wall made of cellulose, a chloroplast for photosynthesis, a large central vacuole for storage, and a similar set of organelles to animal cells. The presence of chloroplasts gives them a distinct green color, and their structured shape is often rectangular or box-like.
Prototype structure of bacterial cells
Bacterial cells are prokaryotic and do not have a defined nucleus. They have a simple structure, consisting of a cell wall, plasma membrane, cytoplasm, and ribosomes. Some bacteria may have additional structures such as flagella for movement or pili for attachment to surfaces.
Diversity of cell size and shape
Cells vary widely in size and shape depending on their function. For example, red blood cells are small and disc-shaped for efficient oxygen transport, while nerve cells can be long and branched to facilitate communication. Size ranges from tiny bacteria (1-10 micrometers) to large plant cells (up to several hundred micrometers).
Cell theory
Cell theory is a fundamental concept in biology. It states that all living organisms are composed of cells, the cell is the basic unit of life, and all cells arise from pre-existing cells. This theory laid the groundwork for modern biology and our understanding of life.
C-value paradox
The C-value paradox refers to the observation that genome size (C-value) does not correlate with the organism's complexity. For instance, some simple organisms possess a larger genome than more complex ones. This discrepancy is often attributed to non-coding DNA, which can vary significantly in size across different species.
Cell Membrane: Chemical components and organization
The cell membrane is primarily composed of a phospholipid bilayer, proteins, cholesterol, and carbohydrates. The fluid mosaic model describes the cell membrane as a dynamic and flexible structure where proteins float in or on the fluid lipid bilayer, allowing for a diverse range of functions.
Membrane transport
Membrane transport mechanisms allow substances to enter or exit a cell. This includes passive transport (diffusion, osmosis) where no energy is required, and active transport (pumps, endocytosis, exocytosis) which requires energy to move substances against their concentration gradient.
Cytoskeleton
The cytoskeleton is a network of protein filaments and tubules that provide structural support, shape, and motility to the cell. It plays a critical role in cell division, intracellular transport, and maintaining the organization of organelles.
Extracellular matrix
The extracellular matrix (ECM) is a complex network of proteins and carbohydrates outside the cell that provides structural and biochemical support to surrounding cells. It plays a crucial role in tissue and organ function, influencing cell behavior and communication.
Structure and Function of Cell organelles: Lysosomes, Vacuoles and micro bodies, Ribosomes, Mitochondria, Chloroplasts, Nucleus
Structure and Function of Cell Organelles
Lysosomes
Lysosomes are membrane-bound organelles containing enzymes that digest cellular waste, macromolecules, and pathogens. They maintain cellular homeostasis by breaking down materials and recycling components.
Vacuoles
Vacuoles are storage organelles found in plant and fungal cells, primarily used for storing nutrients, waste products, and maintaining turgor pressure. They play a role in growth and maintaining cell shape.
Microbodies
Microbodies are small, membrane-bound organelles involved in various metabolic processes. Peroxisomes, a type of microbody, break down fatty acids and detoxify harmful substances.
Ribosomes
Ribosomes are the sites of protein synthesis, composed of ribosomal RNA and proteins. They can be found free in the cytoplasm or attached to the endoplasmic reticulum, translating mRNA into polypeptides.
Mitochondria
Mitochondria are known as the powerhouse of the cell, generating ATP through cellular respiration. They have a double-membrane structure, with their own DNA, and are involved in metabolic processes.
Chloroplasts
Chloroplasts are double-membrane organelles found in plant cells that conduct photosynthesis, converting light energy into chemical energy stored in glucose. They contain chlorophyll, the green pigment essential for this process.
Nucleus
The nucleus is the control center of the cell containing the genetic material, DNA. It regulates gene expression and mediates the replication of DNA during the cell cycle, encased in a double membrane called the nuclear envelope.
Chromosome structure: chromatin and chromosomes organization, euchromatin and heterochromatin, nucleosome, metaphase chromosome, genes and chromosomes, DNA as genetic material, Structure of DNA, Structural and numerical changes in human chromosomes and ploidy in plants, Mutations: Types of mutations, spontaneous and induced mutations, Physical and chemical mutagens
Chromosome structure and mutations
Chromatin and Chromosome Organization
Chromatin is composed of DNA and proteins, forming a complex that packages DNA into a compact structure. Chromosomes are highly organized structures formed during cell division. There are two main types of chromatin: euchromatin, which is less condensed and actively involved in gene expression, and heterochromatin, which is more condensed and typically transcriptionally inactive.
Nucleosome Structure
Nucleosomes are the basic units of DNA packaging, consisting of a segment of DNA wrapped around a core of histone proteins. They play a key role in regulating gene expression and the accessibility of DNA.
Metaphase Chromosome
During metaphase, chromosomes are highly condensed and aligned at the cell's equatorial plane. Each chromosome is composed of two sister chromatids, which are joined at the centromere.
Genes and Chromosomes
Genes are segments of DNA located on chromosomes that encode for proteins and determine inherited traits. The organization of genes on chromosomes affects gene expression and regulation.
DNA as Genetic Material
DNA serves as the hereditary material in all known organisms. Its structure consists of two strands forming a double helix, containing nucleotides made up of a phosphate group, a sugar, and a nitrogenous base.
Structure of DNA
DNA is structured as a double helix, with two strands running in opposite directions. The sugar-phosphate backbone forms the sides, while nitrogenous base pairs connect the two strands.
Chromosome Changes and Ploidy
Structural changes in chromosomes can include duplications, deletions, inversions, and translocations. Numerical changes in chromosomes can lead to conditions such as aneuploidy. Ploidy levels vary in plants, with diploid, haploid, and polyploid forms.
Types of Mutations
Mutations are changes in the DNA sequence. They can be spontaneous or induced by environmental factors. Spontaneous mutations occur naturally, while induced mutations result from exposure to mutagens.
Physical and Chemical Mutagens
Physical mutagens include radiation, which can cause DNA damage. Chemical mutagens are substances that can chemically alter DNA, leading to mutations. Understanding these factors is essential for studying genetic stability and variability.
Cell cycle, Cancer and Cell Signaling: Cell Cycle: Mitosis and Meiosis, Control points in cell-cycle progression, Cell senescence and programmed cell death, Cancer – chromosomal disorders, oncogenes and tumor suppressor genes, Introduction to cell signalling and cell–cell interaction
Cell Cycle, Cancer and Cell Signaling
Cell Cycle Overview
The cell cycle is a series of events that lead to cell division and replication. It comprises four main phases: G1 phase (gap 1), S phase (synthesis), G2 phase (gap 2), and M phase (mitosis). Each phase is characterized by specific cellular activities and regulatory mechanisms.
Mitosis and Meiosis
Mitosis is the process of cell division that results in two identical daughter cells, allowing for growth and repair. It consists of several stages: prophase, metaphase, anaphase, and telophase. Meiosis, on the other hand, is a specialized form of cell division that reduces the chromosome number by half, resulting in four non-identical daughter cells. This process is crucial for sexual reproduction.
Control Points in Cell-Cycle Progression
Cell-cycle checkpoints are critical regulatory mechanisms that assess whether the cell is ready to proceed to the next phase. Key checkpoints include the G1 checkpoint, G2 checkpoint, and the spindle assembly checkpoint. These checkpoints prevent the progression of cells with damaged DNA or incomplete cell division.
Cell Senescence and Programmed Cell Death
Cell senescence is a state of irreversible cell growth arrest that can occur in response to various stressors. It serves as a protective mechanism to prevent the proliferation of damaged cells. Programmed cell death, or apoptosis, is an essential process for maintaining tissue homeostasis and eliminating potentially harmful cells.
Cancer and Chromosomal Disorders
Cancer is characterized by uncontrolled cell growth and division, often resulting from genetic mutations. Chromosomal disorders, such as aneuploidy, involve abnormal numbers of chromosomes and can contribute to tumorigenesis. Understanding the genetic basis of cancer is crucial for developing effective treatments.
Oncogenes and Tumor Suppressor Genes
Oncogenes are mutated forms of genes that normally promote cell division. When activated, they can drive the development of cancer. Tumor suppressor genes, such as TP53, help regulate cell division and prevent tumor formation. Mutations in these genes can lead to uncontrolled cell growth.
Introduction to Cell Signaling
Cell signaling is a complex system of communication that governs basic cellular activities and coordinates cell actions. It involves signaling molecules and receptors that convey information between cells, which is essential for processes such as growth, differentiation, and response to external stimuli.
Cell-Cell Interaction
Cell-cell interactions play a vital role in maintaining tissue structure and function. These interactions are mediated through various types of junctions, such as gap junctions and tight junctions, and signaling pathways that allow cells to communicate and respond to changes in their environment.
Mendelian and nonmendelian genetics: Historical developments, Organisms for genetic experimentation, Mendelian genetics, Allelic interactions: dominance, recessiveness, incomplete dominance, co-dominance, semi-dominance, pleiotropy, Sex determination and sex linkage
Mendelian and Non-Mendelian Genetics
Historical Developments
The foundation of genetics was laid by Gregor Mendel in the mid-19th century through his experiments with pea plants, establishing the laws of inheritance. Non-Mendelian genetics emerged later, addressing patterns not explained by Mendelian principles.
Organisms for Genetic Experimentation
Mendel used pea plants (Pisum sativum) for his studies due to their clear traits and ability to self-pollinate. Other organisms commonly used in genetic experimentation include fruit flies (Drosophila melanogaster), mice (Mus musculus), and Arabidopsis thaliana.
Mendelian Genetics
Mendelian genetics refers to the set of principles related to the inheritance of traits by genes, based on Mendel's laws of segregation and independent assortment. It emphasizes discrete units of inheritance.
Allelic Interactions
Allelic interactions determine the expression of traits and include: - Dominance: Phenomenon where one allele masks the expression of another. - Recessiveness: An allele that does not manifest in the presence of a dominant allele. - Incomplete dominance: A blending of traits when both alleles are expressed. - Co-dominance: Both alleles contribute equally to the phenotype. - Semi-dominance: Similar to incomplete dominance, but the phenotype shows a gradient rather than a blend. - Pleiotropy: One gene influences multiple phenotypic traits.
Sex Determination and Sex Linkage
Sex determination mechanisms include chromosomal (e.g., XX-XY system) and environmental factors. Sex-linked traits are usually associated with genes on sex chromosomes, particularly the X chromosome, leading to conditions like hemophilia and color blindness.
Linkage, crossing over and population genetics: Linkage, crossing–over, chromosome and genetic mapping, Extra chromosomal inheritance, Genetic Code, Mutations, Evolution and population genetics: Hardy Weinberg law, allelic and genotype frequencies, evolutionary genetics, natural selection
Linkage, Crossing Over, and Population Genetics
Linkage refers to the tendency of genes located close to each other on a chromosome to be inherited together during meiosis. This occurs because the chance of crossing over between two genes is less likely when they are physically closer together. Understanding linkage is important for constructing genetic maps and understanding inheritance patterns.
Crossing over is the process during meiosis where homologous chromosomes exchange segments of genetic material. This increases genetic diversity by producing new combinations of alleles. The frequency of crossing over between two genes can be used to estimate the distance between them on a chromosome.
Genetic mapping involves determining the location and distance between genes on a chromosome. It utilizes the principles of linkage and crossing over to create maps that can predict inheritance patterns and identify genes associated with specific traits or diseases.
Extra chromosomal inheritance refers to the transmission of genetic material that occurs outside of the nuclear DNA, such as mitochondrial DNA. This type of inheritance often involves organelles and can follow different patterns than nuclear inheritance, sometimes leading to maternal inheritance patterns.
The genetic code is the set of rules by which information encoded in genetic material is translated into proteins. It consists of codons, sequences of three nucleotides that correspond to specific amino acids or stop signals during protein synthesis. Understanding the genetic code is crucial for molecular biology and genetics.
Mutations are changes in the DNA sequence that can lead to different traits or diseases. They can occur naturally or be induced by environmental factors. Types of mutations include point mutations, insertions, deletions, and larger chromosomal alterations. Mutations are the source of genetic variation and are fundamental to the process of evolution.
Population genetics studies the distribution and change in frequency of alleles within populations. It examines the mechanisms of evolution, including natural selection, genetic drift, mutation, and gene flow. The Hardy-Weinberg law provides a mathematical framework for understanding genetic variation in populations under certain conditions, aiding in the analysis of evolutionary processes. Allelic and genotype frequencies are key metrics in population genetics and are influenced by reproduction, selection, and migration.
Cytological techniques: Microscopy and staining techniques, Microtomy, Karyotyping, Chromosome banding, in situ hybridization and FISH, chromosome painting, Fluorescence Activated Cell Sorting
Cytological techniques
Microscopy and staining techniques
Microscopy is essential for visualizing cellular structures. Common types include light microscopy, electron microscopy, and fluorescence microscopy. Staining techniques enhance contrast in specimens for easier observation. Common stains include haematoxylin and eosin, Giemsa stain, and immunohistochemical stains.
Microtomy
Microtomy is the technique of slicing specimens into very thin sections for microscopic examination. This is typically done using a microtome. High-quality sections are essential for accurate cellular analysis and are usually mounted on slides for observation.
Karyotyping
Karyotyping involves the systematic examination of chromosome number and structure. It is used to identify chromosomal abnormalities and understand genetic diseases through analysis of metaphase chromosomes.
Chromosome banding
Chromosome banding techniques, such as G-banding, allow for the visualization of chromosomal structures based on the chromatin's density. This method helps in identifying specific chromosomal anomalies and characteristics.
In situ hybridization and FISH
In situ hybridization is a technique used to locate specific nucleic acid sequences within fixed tissues or cells. Fluorescence In Situ Hybridization (FISH) utilizes fluorescent probes to detect and localize specific DNA sequences, aiding in the detection of genetic disorders.
Chromosome painting
Chromosome painting involves the use of fluorescently labeled DNA probes that bind to specific chromosome regions. This technique allows researchers to visualize the whole chromosome and assess structural relationships.
Fluorescence Activated Cell Sorting
Fluorescence Activated Cell Sorting (FACS) is a specialized type of flow cytometry that sorts a heterogeneous mixture of cells into distinct populations based on specific light scattering and fluorescent characteristics. FACS is invaluable for isolating specific cell types for further study.
