Chapter 1: Genetics of Life

I. Fundamentals of Genetics and DNA

A. Gene Editing and DNA Structure

• The Nobel Prize in Chemistry for 2020 was shared by Emmanuelle Charpentier and Jennifer A. Doudna for developing the methodology of Gene Editing.
• The technology discovered is called CRISPR-Cas 9, a gene editing process that can bring desirable changes in the genes in DNA.
• This discovery is expected to make revolutionary advances in genetic disease therapy, treatment of cancer, and development of crops resistant to pests and diseases.
• A deeper understanding of DNA (Deoxyribonucleic acid) and genes paved the way for gene editing.
• The double helical model of DNA was presented in 1953 by James Watson and Francis Crick. They based their structure on X-ray diffraction studies conducted by Rosalind Franklin (who took the crucial 'Photo 51') and Maurice Wilkins.

B. Components of DNA and RNA

• The basic building block of DNA is the Nucleotide.
• Each nucleotide is composed of a deoxyribose sugar, a phosphate group, and a nitrogen base.
• The nitrogen bases in DNA are Thymine (T), Adenine (A), Guanine (G), and Cytosine (C).
• The strands of DNA are composed of sugar and phosphate molecules. The rungs are formed by the pairing of nitrogen bases.
• DNA size: The DNA in each chromosome is about 2 inches (5 cm) long; if joined together from all 46 human chromosomes, it would be around 6 feet (2 m).
• RNA (Ribonucleic acid) is another type of nucleic acid, also made up of nucleotides.
• RNA nucleotides contain a ribose sugar, a phosphate group, and nitrogenous bases: Adenine, Guanine, Uracil (U), and Cytosine.
• Most RNAs have a single strand.

C. Genes and Chromosomes

• A Gene is a specific sequence of nucleotides in DNA.
• Genes provide instructions for the synthesis of proteins, which are responsible for forming characteristic features and controlling metabolic activities.
• DNA and histone proteins are the primary components of a chromosome.
• Chromosome Formation: Eight histone proteins join to form a histone octamer. DNA strands wind around this octamer to form a structure called a nucleosome. Chromosomes are formed by packing, coiling, and recoiling numerous nucleosomes.
• Chromatids are the parts of a chromosome connected by a centromere.

D. Human Chromosomes and Genetic Constitution

• Somatic chromosomes control physical characteristics; humans have twenty-two pairs. A pair of identical chromosomes forms a homologous chromosome, one inherited from the mother and one from the father.
• Sex Chromosomes (X and Y) are involved in sex determination. The Y chromosome is comparatively smaller than the X chromosome. The SRY gene on the Y chromosome is responsible for the development of the testis in the embryo.
• Normal female genetic constitution is 44 + XX, and normal male is 44 + XY.
• Variant Genetic Constitutions influence physical and mental development:
  • Turner syndrome (44 + X0): Females with only one X chromosome; may not develop female sexual characteristics during adolescence.
  • Klinefelter syndrome (44 + XXY): Males with two X chromosomes and one Y chromosome; may exhibit female characteristics.

II. Protein Synthesis

• Protein synthesis is the result of the action of genes.

Stage	Location	Process	Components Involved
1. Transcription	Nucleus	mRNA (messenger RNA) is formed from a specific nucleotide sequence (gene) in DNA with the help of various enzymes. mRNA carries messages for protein synthesis.	DNA, mRNA, Enzymes
2. Translation	Cytoplasm	tRNAs (transfer RNA) carry specific amino acids to the ribosome based on the mRNA message. rRNAs (ribosomal RNA), which are part of ribosomes, combine amino acids to make protein.	mRNA, tRNA, Ribosome (rRNA), Amino acids

III. Mendelian and Non-Mendelian Genetics

A. Foundation of Genetics

• Genetics is the branch of science dealing with genes, heredity, and variation.
• Gregor Johann Mendel (1822–1884) is considered the father of genetics. He laid the foundation through hybridisation experiments on pea plants (Pisum sativum).
• Mendel hypothesized that characters are passed on through certain factors (now known as genes).
• Alleles are different forms of a gene that determine a character.
• Phenotype is the observable characteristic of an organism.
• Genotype is the genetic constitution responsible for these characteristics.

B. Mendel's Postulates (Monohybrid Cross Inferences)

• A trait is controlled by two factors.
• In hybridisation involving contrasting traits, the dominant trait is expressed in the F1 generation, while the recessive trait remains hidden.
• The ratio of dominant to recessive traits in the F2 generation is 3:1.
• The factors (genes) that determine a trait separate without mixing when gametes are formed.
• Dihybrid Cross Inference: When two or more different traits are combined, each trait is inherited independently to the next generation without mixing.

C. Non-Mendelian Inheritance

• This concept arose from limitations in Mendel’s laws regarding complex gene interactions.

Inheritance Type	Peculiarity and Reason	Example
Incomplete Dominance	A dominant allele cannot fully hide the recessive allele.	Red flowered x White flowered four o’clock plant = Pink flowers.
Co-dominance	Both alleles exhibit their traits at the same time.	Roan coat pattern in cattle/horses; ABO blood group determination.
Multiple Allelism	The gene determining a character has more than two alleles (e.g., IA, IB, and i determine ABO blood group).	ABO blood group in humans.
Polygenic inheritance	More than one gene controls the character, causing variation in expression (e.g., melanin production).	Difference in skin colour.

IV. Genetic Processes Causing Variation

• Heredity (transmission of parental traits) and Variation (differences from parents) are both influenced by inherited genes.
• 1. Crossing Over: Occurs during the first phase of meiosis.
  • Homologous chromosomes pair.
  • Chromatids break and segments are exchanged at the point of contact, called the chiasma.
  • This exchange causes a recombination of alleles, leading to the appearance of new traits in the offspring.
• 2. Mutation: A sudden heritable change in the genetic constitution of an organism.
  • Causes: Errors during DNA replication, exposure to certain chemicals, or radiations.
  • Mutations cause changes in genes, which are transferred through generations, playing a crucial role in the process of evolution.

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Chapter 2: Paths of Evolution

I. Early Theories of Evolution

A. Lamarckism (Theory of Inheritance of Acquired Characters)

• Proposed by French biologist Jean Baptiste Lamarck.
• Idea: Organisms acquired characters during their lifetime due to environmental changes (e.g., a giraffe stretching its neck to reach higher leaves) and transmitted these acquired characters through generations.
• This theory was later rejected as scientists proved that acquired characters do not impart changes in the genetic structure of organisms and are therefore not inherited.

B. Darwinism (The Theory of Natural Selection)

• Proposed by English naturalist Charles Darwin (1809–1882), marking the foundation of modern evolutionary perspectives.
• Darwin’s studies, including his observations during the voyage on the H M S Beagle (1831), documented the diversity of flora and fauna (like the Galapagos finches).
• He elaborated his ideas in the book On the Origin of Species (1859).

C. Key Concepts of Natural Selection

1. Overproduction: Organisms produce more offspring than the environment can support.
2. Variations: Organisms show differences in features (size, immunity, etc.). These variations can be favourable or harmful.
3. Struggle for Existence: Competition arises due to the limitation of resources (food, shelter, mates).
4. Survival of the Fittest: Organisms possessing favourable variations survive in the struggle and reproduce more effectively.
5. Natural Selection: Favourable variations are passed on to the next generations. Over time, accumulated variations lead to the evolution of new species.

D. Neo Darwinism

• Darwin’s theory initially lacked the genetic basis for variations and inheritance.
• Neo Darwinism incorporated the discoveries of Gregor Mendel and concepts of chromosomes and genes.
• The causes of variations leading to evolution are understood to be genetic changes, genetic recombination during sexual reproduction, and gene flow.

II. Speciation and Evidences of Evolution

A. Speciation

• Speciation is the process where new species arise from a common ancestor, leading to biodiversity.
• All species are thought to have descended from a Last Universal Common Ancestor (LUCA), and species may share a Most Recent Common Ancestor (MRCA).
• When members of a population become isolated by ecological or other factors (like mutation, natural selection, genetic recombination), variations accumulate. When they become unable to reproduce mutually, they evolve into different species.

B. Evidences Supporting Evolution

1. Molecular Biology: Evolutionary relationships are determined by comparing the sequence of nucleotides in DNA and amino acids in proteins.
   • Example: Humans and chimpanzees show 0 difference in the amino acids of the haemoglobin beta chain, indicating a close evolutionary relationship.
2. Comparative Anatomy: The comparative study of anatomy shows similarities in the internal structure of different organisms, despite differences in external structure and function.
   • Example: The bones in the forelimbs of humans and cats, the flippers of whales, and the wings of bats are similar.
3. Fossil Evidences: Fossils are the remains or traces of ancient organisms that validate evolution as a gradual process.
   • Connecting links reveal evolutionary relationships (e.g., Archaeopteryx possesses features of both reptiles and birds).

III. Human Evolution

A. Primate Ancestry

• The common ancestors of mammals like monkeys, apes, and humans belonged to the group of primates.
• Common characteristics of primates include an opposable thumb and binocular vision.
• Apes and humans belong to the category Hominoidea.

B. Stages in Human Evolutionary Path

• The increase in brain capacity (cranial capacity) is a major evolutionary trend in humans, enabling complex social behaviour, tool making, language, and higher-level cognitive functions.

Member	Cranial Capacity	Key Characteristics
Sahelanthropus tchadensis	350 cm³	First link in the human evolutionary series.
Australopithecus	450 cm³	Skeletal structure confirms bipedalism (walking on two legs).
Homo habilis	600 cm³	Made tools with stones using hands, lived in small groups, began hunting.
Homo erectus	900 cm³	Able to walk upright on two legs, omnivores, used excellent stone weapons.
Homo neanderthalensis	1450 cm³	Contemporaries of modern man, small sloping forehead, buried dead bodies.
Homo sapiens	1350 cm³	Modern man, acquired technology and agricultural methods, built cities, culturally most evolved.

IV. The Nervous System

A. Neuron Structure and Function

• Neurons (Nerve cells) are the basic building blocks of the nervous system. They receive stimuli and form suitable messages.
• Cell body (cyton): Contains cell membrane, cytoplasm, nucleus, and organelles.
• Dendrons: Fine fibres arising from the cell body; their branches are Dendrites, which receive messages from adjacent neurons and transmit them to the cyton.
• Axon: The longest fibre from the cell body; impulses travel through the axon to the Axonites (its branches).
• Synaptic knob: Knob-like structure at the tip of the axonite; contains neurotransmitter (e.g., Acetylcholine) to transfer chemical messages.
• Myelin sheath: A layer covering some axons, made of shiny white fat (Myelin). Functions: increases impulse transmission speed, acts as an insulator, nourishes the neuron, protects the axon.
  • Myelin sheath is produced by oligodendrocytes in the brain/spinal cord (forming white matter) and by Schwann cells in the nerves.

B. Impulse Transmission and Synapse

• Impulse Transmission: When a neuron is stimulated, positive ions enter the cell, causing a temporary charge variation. The nerve impulse is the message transmitted.
• Synapse: The part where an impulse is transferred from one neuron to another.
  • When impulses reach the synaptic knob, it secretes neurotransmitters into the synaptic cleft (gap).
  • Neurotransmitters bind with receptors on the post synaptic membrane of the next neuron, stimulating it.
  • Synapses transmit impulses in only one direction and increase the speed of the impulses.
• Neocortex: The complex six-layered cerebral cortex in mammals, highly developed in humans (approx. 16 billion neurons). Synapses in the neocortex facilitate advanced mental processes like thinking, decision-making, learning, and recalling.

C. Central Nervous System (CNS)

• The CNS consists of the Brain and Spinal Cord.
• Protection: Covered by three-layered Meninges. The cerebrospinal fluid (CSF) fills the space between the inner membranes, cavities of the brain, and the central canal. CSF provides oxygen/nutrients, eliminates wastes, regulates pressure, and protects from injury.

Part of the Brain	Functions/Peculiarities
Cerebrum	Largest part; centre of memory, intelligence, thinking, imagination, and sensory experiences. Outer part is cortex (grey matter), inner part is medulla (white matter). Controls problem-solving, planning, and voluntary movements.
Cerebellum	Second largest part; coordinates muscular activities to maintain body equilibrium.
Thalamus	Acts as the relay station of messages to and from the cerebrum.
Hypothalamus	Helps maintain homeostasis by regulating body temperature, hunger, thirst, and emotions.
Medulla oblongata	Controls involuntary activities (heartbeat, ventilation, vomiting, cough, sneezing).
Spinal Cord	Continuation of medulla oblongata. Transmits messages between body parts and the brain. Has grey matter (inner) and white matter (outer).

D. Peripheral Nervous System (PNS)

• Includes 12 pairs of cranial nerves and 31 pairs of spinal nerves, receptors, and nerve ganglia.
• Nerves: Made up of axons of neurons covered with fat/connective tissue.
• Autonomous Nervous System (ANS): Part of the PNS that regulates body activities involuntarily.
  • Sympathetic system: Equips the body for emergency situations (e.g., dilates pupil, increases heartbeat).
  • Parasympathetic system: Prepares the body to relax and perform routine functions (e.g., constricts pupil, slows heartbeat).

E. Spontaneous Responses

• Reflex actions are reactions that occur spontaneously and involuntarily in response to stimuli. They can originate from both the spinal cord and the brain.
• The pathway of impulses in a reflex action is called a reflex arc.

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Chapter 3: Behind Sensations

I. Sensing Stimuli

• Stimuli are circumstances leading to responses (can be external or internal).
• The body recognizes stimuli through specialized cells or nerve endings called Sensory Receptors.
• Electrical impulses (receptor potential) are produced in receptors. When concentrated, this forms action potential in neurons, traveling as nerve impulses.
• General Senses (touch, pain, heat, pressure) are detected by receptors in the skin, muscles, joints, internal organs, and blood vessels.
• Special Senses (vision, hearing, taste, smell) are detected by receptors concentrated in specific organs.

II. Vision (The Eye)

A. Protection and Chambers

• The Conjunctiva covers the anterior part of the eye (except the cornea), protecting, moisturizing, and lubricating it.
• Lacrimal glands produce tears, which contain the enzyme lysozyme to protect against infections, keep the surface moist, and provide nutrients.
• Aqueous chamber (between cornea and lens) contains watery aqueous humor. This fluid provides oxygen and nutrients to the lens and cornea and helps regulate pressure.
• Vitreous chamber (between lens and retina) contains transparent jelly-like vitreous humor, which maintains the shape of the eyeball.

B. Layers and Associated Parts

Layer	Part	Characteristic/Function
Sclera (Outer)	Cornea	Transparent anterior part, allows light to enter the eye.
Choroid (Middle)	Iris	Contains melanin pigment, regulates the amount of light by controlling pupil size using radial and circular muscles.
	Lens	Convex structure, attached to ciliary muscles by ligaments. Forms a small, real, and inverted image on the retina. Its curvature is changed by ciliary muscles to enable the power of accommodation (focusing on near/distant objects).
Retina (Inner)	Photoreceptor cells	Contains rod cells and cone cells. Image is formed here.
	Yellow spot (Macula)	Area in the middle of the retina where cone cells are abundant.
	Blind spot	Area where the optic nerve originates; contains no photoreceptors, thus having no vision.

C. Photoreceptors and Vision

• Rod Cells (9+ crore): Recognize objects in dim light and shades of black and white; pigment is rhodopsin.
• Cone Cells (45 lakh): Provide vision in intense light and help recognize colours; pigment is photopsin.
• Both rhodopsin and photopsin contain the components opsin and retinal (formed from Vitamin A).
• Colour Vision: Three types of cone cells recognize primary colours: S-cones (blue light), M-cones (green light), and L-cones (red light). Colour perception is formed by stimulating these cones in varying proportions.
• Binocular Fusion: Since each eye receives slightly different images, the visual centre in the brain compares and combines (fuses) them, which enables 3D vision and depth perception.

III. Hearing and Balance (The Ear)

A. Hearing Mechanism

• Pinna: Directs sound waves into the auditory canal.
• Auditory Canal: Directs sound waves to the tympanum (eardrum).
• Tympanum: Vibrates according to sound waves.
• Ear Ossicles (Malleus, Incus, Stapes): Vibrate the vibrations from the tympanum.
• Eustachian canal: Connects the middle ear to the pharynx; helps balance pressure on both sides of the tympanum.
• Inner Ear (Cochlea): A snail-shell structure with three chambers.
  • Vibrations pass through the oval window.
  • Upper and lower chambers contain perilymph; the middle chamber contains endolymph.
  • The Organ of Corti, containing auditory receptors (hair cells), is situated in the basilar membrane.
  • Vibrations stimulate hair cells, generating impulses that reach the brain via the auditory nerve, resulting in hearing.

B. Body Balance

• The vestibular system in the inner ear maintains body balance.
• This system includes three semicircular canals (arranged perpendicular to each other) and the vestibule (containing the utricle and saccule).
• Rotational movement of the head moves the endolymph in the canals, stimulating hair cells. Linear movement stimulates hair cells in the utricle and saccule.
• These impulses reach the brain through the vestibular nerve.

IV. Smell and Taste

• Olfaction (Smell): Particles responsible for smell enter the nasal cavity and dissolve in the mucus secreted by the mucus membrane. Millions of olfactory receptor neurons are stimulated, generating impulses that travel through the olfactory nerve to the brain.
• Taste (Gustation): Taste buds are located in the papilla of the tongue.
  • Taste buds contain about 100 chemoreceptors.
  • Substances that give rise to taste dissolve in saliva and stimulate chemoreceptors.
  • The main tastes recognised are sweet, sour, salty, pungent, bitter, and umami.

V. Skin Sensation

• The skin contains various specialized receptors (nocireceptors, Merkel discs, Meissner corpuscles, etc.) to detect general senses like pain, temperature fluctuations, touch, pressure, and vibration.
• Pain (Nociception): The process of identifying pain is done by specialized nerve endings called nocireceptors found throughout the skin, muscles, and internal organs.

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Chapter 4: Chemoreception in Organisms

I. Hormone Action and Plant Hormones

A. Hormone Mechanism

• Hormones are chemical messengers that control and coordinate body functions along with the nervous system.
• A Target cell is a cell on which a hormone acts.
• Target cells have specific receptors (in the cell membrane or within the cell).
• Hormones combine with their receptors to form a hormone-receptor complex, which controls activities inside the cell.
• Transport: Animal hormones travel via blood from endocrine glands. Plant hormones travel via cell-to-cell transport or through xylem and phloem.

B. Plant Hormones and Functions

Hormone	Functions
Auxins	Increases stem length, inhibits lateral bud growth, regulates tropic movements, stimulates flower and fruit formation. Auxins move away from light, causing stem elongation on the shaded side (bending).
Gibberellins	Break seed dormancy, stimulate cell division in stems and roots, influence the growth of fruits and seeds.
Cytokinins	Stimulate cell division and differentiation, stimulate lateral bud growth, delay senescence, retains green colour of leaves, promotes nutrient transport.
Ethylene	Plays a role in the ageing of leaves/flowers, and the ripening of fruits.
Abscisic Acid (ABA)	Inhibits growth, maintains seed dormancy until favourable conditions arise, promotes abscission of mature leaves/fruits.

• Photoperiodism: The response of plants to the duration of day and night, regulating processes like flowering. Phytochrome (a light-sensitive pigment) perceives the photoperiod.

II. Human Hormonal Control

A. Thyroid Gland (Metabolism and Calcium)

• Located in the neck. Contains Follicular cells (produce thyroxine) and Parafollicular cells (produce calcitonin).
• Thyroxine: Controls metabolism, body temperature, brain development in children, and maintains the health of the heart, skin, and reproductive system.
• Thyroid Disorders: Hypothyroidism (reduced thyroxine: decreased metabolism, weight gain, slow heart rate); Hyperthyroidism (excessive thyroxine: increased metabolism, weight loss, increased heart rate).
• Calcitonin: Reduces the level of calcium in the blood (Normal level: 9–11 mg/dL). Inhibits the mixing of calcium from bone into the blood.

B. Parathyroid Gland (Calcium Regulation)

• Located behind the thyroid gland. Produces Parathormone.
• Parathormone: Increases calcium level in the blood by stimulating the mixing of calcium and phosphate from the bone into the blood and accelerating the reabsorption of calcium to blood.

C. Pancreas (Glucose Regulation)

• Contains a group of cells called the Islets of Langerhans.
  • Alpha cells produce Glucagon.
  • Beta cells produce Insulin.
• Normal blood glucose: Fasting: 70–100 mg/dL.
• Insulin Action: Decreases blood glucose by accelerating glucose entry into cells and converting glucose to glycogen in the liver/tissues.
• Glucagon Action: Increases blood glucose by converting glycogen to glucose in the liver, and converting amino acids to glucose.
• Diabetes Mellitus: Blood glucose level rises above normal (FBS > 126 mg/dL). Type II diabetes is often linked to lifestyle factors and decreased insulin effectiveness. Type I diabetes is caused by the destruction of beta cells leading to loss of insulin production.

D. Adrenal Gland (Emergency Response)

• Located above the kidney.
• Medulla (Inner part): Secretes Epinephrine and Norepinephrine. These hormones prepare the body for emergency by increasing heart rate, blood pressure, blood glucose levels, and blood flow to the heart and muscles.
• Cortex (Outer part): Produces corticosteroids (glucocorticoids, mineralocorticoids, gonadocorticoids).
  • Cortisol: Maintains glucose homeostasis, suppresses immune responses, and resists inflammation/allergy.
  • Aldosterone: Helps maintain mineral equilibrium and regulates blood pressure.

E. Master Control System

• Hypothalamus: Considered the master controller. Controls the pituitary gland by regulating the production of tropic hormones. Produces Releasing hormones and Inhibitory hormones that act on the anterior lobe.
• Pituitary Gland:
  • Anterior Lobe: Secretes Tropic hormones (TSH, ACTH, GTH), Prolactin (milk production), and Somatotropin (GH) (body growth).
  • Posterior Lobe: Stores and secretes Vasopressin (ADH) (reabsorption of water from kidney) and Oxytocin (lactation, smooth muscle contraction), which are produced by the hypothalamus.
• Growth Disorders (Somatotropin): Dwarfism (decreased GH during growth phase), Gigantism (increased GH during growth phase), Acromegaly (increased GH after growth phase, affects palms, feet, jaws).

F. Other Hormonal Functions

• Pineal Gland: Produces Melatonin, which influences sleep and wakefulness; known as the biological clock.
• Thymus Gland: Produces Thymosin, essential for the maturation of T lymphocytes (related to immunity).
• Appetite Hormones: Ghrelin (hunger hormone, produced by stomach lining) stimulates appetite. Leptin (satiety hormone, produced by adipose tissue) reduces appetite.

III. Pheromones (External Chemical Communication)

• Pheromones are chemical substances secreted externally by organisms to facilitate communication with the same species.
• They are volatile substances.
• Functions include: Trail pheromone (marking paths), Sex pheromone (attracting mates), Alarm pheromone (signalling dangers), and Territorial pheromone (determining territory).

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Chapter 5: Immunity and Healthcare

I. Immunity and Defence Mechanisms

A. Health and Antigens

• Health is defined as a complete state of physical, mental, and social well-being.
• Antigens are substances (pathogens, pollen, dust, chemicals) that enter the body and cause disease.
• Immunity is the body's ability to prevent pathogens from entering and destroy those already inside.

B. Innate Immunity (Non-Specific Immunity)

• This natural immune mechanism exists in the body by birth and is non-specific (works against any type of pathogen).
• Primary Level (Barriers): Includes physical and chemical defenses:
  • Lysozyme (in saliva and tears), Mucus/Mucus membrane, Cilia (in the trachea), Sweat/Sebum (on the skin), HCl (in the stomach), Useful bacteria, and Wax (in the ear).
• Secondary Level (Internal Defence): Coordinates action to destroy pathogens that have entered.
  • Phagocytosis: The process by which phagocytes (like Neutrophils and Monocytes) engulf and destroy pathogens. The pathogen is enclosed in a phagosome, which fuses with a lysosome to form a phagolysosome for destruction.
  • Inflammatory Response: Injured cells release histamine, dilating blood vessels, increasing blood flow, and bringing WBCs (monocytes and neutrophils) to fight infection.
  • Fever: High body temperature (above 98.6°F) triggered by pyrogens released by WBCs. Fever helps phagocytes destroy pathogens faster and inhibits pathogen growth.
  • Clotting of Blood: A mechanism to prevent blood flow and block pathogen entry. Platelets/damaged tissues produce thromboplastin, which converts prothrombin to thrombin. Thrombin converts fibrinogen to fibrin, forming a clot.

C. Acquired Immunity (Specific Immunity)

• This immunity develops after birth and specifically recognizes and defends antigens.
• Carried out primarily by Lymphocytes:
  • B Lymphocytes: Form and mature in bone marrow. Produce proteins called antibodies that act against antigens.
  • T Lymphocytes: Form in bone marrow and mature in the thymus gland. Identify and destroy infected cells and cancer cells.
• Artificial Immunity (Immunisation): Achieved through Vaccines (substances that act as antigens). Vaccines stimulate the immune system to produce antibodies, providing long-term protection.

II. Diseases

A. Communicable Diseases (Pathogen-based)

• Spread through direct contact, contaminated food/water, air droplets (coughing/sneezing), or surfaces.
• Bacterial: Tuberculosis (Mycobacterium tuberculosis), Rat fever (Leptospira). Bacteria release toxins or enzymes that destroy host tissues.
• Viral: AIDS (HIV attacks and destroys T lymphocytes, reducing immunity); Nipah. Viruses multiply using the host's genetic mechanism, destroying cells.
• Protozoan: Malaria (Plasmodium, transmitted by Female Anopheles mosquito, destroys RBCs); Amoebic encephalitis (Naegleria fowleri).
• Worm Infestations: Caused by parasitic worms (pin worm, round worm). Filariasis is caused by filarial worms transmitted by the Female Culex mosquito, lodging in lymphatic vessels and causing swelling.

B. Non-Contagious Diseases

• Cancer: Abnormal and uncontrolled cell division spreading through blood and lymph. Caused by genetic changes, environmental factors, viral infections, and lifestyle.
• Lifestyle Diseases: Diabetes Mellitus, Hypertension.
• Hereditary Diseases (Genetic Defects):
  • Sickle cell anaemia: Defect in the gene controlling haemoglobin, causing red blood cells to become sickle-shaped, which reduces oxygen capacity and blocks blood flow.
  • Haemophilia: Defect in the gene controlling blood clotting proteins, leading to excessive bleeding.

III. Healthcare and Technology

A. Systems of Treatment

• Ayurveda: Traditional Indian system focused on diet, herbal medicines, and exercise. Charaka is known as the Father of the Ayurvedic system.
• Homeopathy: Introduced by Samuel Hahnemann; uses diluted doses of natural substances.
• Modern Medicine: Founded by Hippocrates; emphasizes pathogens, diagnosis (laboratory tests, body check-ups), and treatment (medicine, surgery, organ transplantation).

B. Antibiotics and Blood Transfusion

• Antibiotics: Medicines derived from microorganisms or produced synthetically, used against bacteria. Excessive use can cause side effects (digestive issues, allergy, organ damage) and lead to Antibiotic Resistance. Penicillin was the first antibiotic, discovered by Alexander Fleming in 1928.
• Blood Transfusion: Requires careful consideration of blood groups.
  • Blood groups are determined by A antigen and B antigen on the surface of RBCs.
  • The Rhesus factor (Rh factor), or D antigen, determines positive or negative blood group.
  • If the donor’s antigen is absent in the recipient, antibodies in the recipient’s plasma may cause agglutination (clotting).

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Chapter 6: Biology and Technology

I. Genetic Engineering

A. Core Technologies

• Biotechnology: The technology of using living things or their parts to provide useful products and services to humans.
• Genetic Engineering: Technology used to create desired traits in organisms by combining or deleting genes.
• Recombinant DNA Technology (rDNA): Combines DNA segments from two or more organisms to form recombinant DNA.
  • Key tools: Restriction Endonuclease Enzyme (cuts specific genes/genetic scissors) and Ligase enzyme (joins DNA segments/genetic glue).
  • Vectors (like bacterial plasmids or some viruses) carry the genes into a host cell.
• CRISPR Technology: A modern, precise technology used for gene editing.
  • It uses the Cas9 enzyme (as scissors to cut DNA) and guide RNA (gRNA) (identifies the DNA segment to be cut).
  • This technology enables the editing of the nitrogen base sequence in DNA to remove unwanted characteristics or add new ones.
• Genetically Modified Organisms (GMOs): Plants, animals, or microorganisms whose genetic constitutions have been altered through genetic engineering. Examples include Bt. Cotton (pest resistance), Golden rice (nutrient-enriched), and E. coli used to produce insulin.

B. Genome Mapping and Therapy

• Genome: The sum total of all the genetic materials in an organism.
• Human Genome Project (HGP): A global scientific initiative (1990–2003) to sequence and understand the human genome.
  • Discoveries: The human genome has approximately 300 crore base pairs and 20,000 to 25,000 genes. Only about 1–2% of the genome is functional genes.
• Gene Therapy: The method of treating diseases by removing defective genes and replacing them with functional genes.
  • Somatic gene therapy: Affects body cells; changes are not transmitted to the next generation.
  • Germline gene therapy: Affects reproductive cells; changes are transmitted to the next generation.
  • Stem Cell Therapy: Used, for example, to treat sickle cell anaemia by incorporating the active gene into stem cells using viruses as vectors and injecting them back into the patient.

C. DNA Fingerprinting

• Discovered by British geneticist Sir Alex Jeffrey in 1984.
• Basis: While 99.9% of DNA is the same in all humans, the remaining 0.1% varies. These differences (specifically in the repeated sequences of nucleotides in non-protein-coding regions) are unique to each individual.
• Uses: To identify culprits, determine biological relationships between parents and offspring, identify victims of accidents/disasters, and track endangered species.

II. Advanced Biological Fields

A. Human Microbiome

• Human Microbiome: The collection of microorganisms (bacteria, archaea, fungi, viruses) and their genes that inhabit the human body.
• The microorganisms provide crucial services, including immunity, digestion, and the production/absorption of vitamins.
• Human Microbiome Project (HMP): Launched in 2007 to develop knowledge about this community. It revealed that disease can result from a change in the equilibrium of these microorganisms.
• Poop Pills (Fecal Microbiota Transplant): A treatment for serious infections caused by drug-resistant bacteria (like Clostridium difficile), involving transferring beneficial bacteria from healthy faeces.

B. Biology and Artificial Intelligence (AI)

• AI is used widely in biology, including:
  • Diagnosis and Treatment: Discovering new drugs, predicting effectiveness of substances, and recommending suitable treatments.
  • Personalised Medicine: Analyzing an individual’s genetic makeup and health information for customized treatment regimens.
  • Improving Agriculture: Monitoring soil health and predicting crop diseases.
  • Bioinformatics: A scientific discipline that analyzes large amounts of biological data by combining computer science, mathematics, and statistics.

C. Environmental Conservation Technology

• Cryopreservation: Preservation of living cells, tissues, and organs at very low temperatures (-196°C).
• Bioremediation: Uses microorganisms and plants to remove pollutants from contaminated environments (soil, water, air), converting them into harmless compounds.
• Wildlife Tracking Sensors: Used by researchers to monitor animal movement and behaviour for conservation strategies.