Chapter 1: Genetics of Life
I. Introduction to Genetics and Gene Editing
- Gene Editing involves methodologies to bring desirable changes in the genes in DNA.
- The Nobel Prize in Chemistry (2020) was shared by Emmanuelle Charpentier and Jennifer A Doudna for the discovery of CRISPR-Cas 9, a gene editing technology.
- CRISPR-Cas 9 is expected to make revolutionary
advances in genetic disease therapy and cancer treatment, and can also
be used to develop crops resistant to pests and diseases.
- A deeper understanding of DNA (Deoxyribonucleic acid) and genes paved the way for gene editing.
II. The Structure and Location of DNA
- Location: DNA is found within the chromosomes inside the cell nucleus.
- Discovery: James Watson and Francis Crick presented
the double helical model of DNA in 1953, based on X-ray diffraction
studies, including the crucial image 'Photo 51' taken by Rosalind
Franklin.
- DNA Structure:
- It is composed of two strands.
- The strands are made up of sugar (deoxyribose) and phosphate molecules.
- The structure resembles a double helix.
- Nucleotide: This is the basic building block of
DNA, composed of a deoxyribose sugar (a 5-carbon sugar), a phosphate
group, and a nitrogen base.
- Nitrogen Bases: Adenine, Thymine, Guanine, and Cytosine.
- Rungs (formed by paired bases) link the strands.
- Pairing Mode: Nitrogen base pairing forms the rungs: Adenine pairs with Thymine (A-T), and Guanine pairs with Cytosine (G-C).
III. Chromosome Structure and Types
- Chromosome Components: DNA and histone proteins are the primary components.
- Nucleosome Formation: Eight histone proteins join to form a histone octamer. DNA strands wind around this octamer to form a nucleosome.
- Chromosome Formation: Chromosomes are formed by the packing, coiling, and recoiling of numerous nucleosomes.
- Chromatids: These are parts of a chromosome connected by a centromere.
- Human Chromosomes:
- Humans have a specific number of chromosomes.
- Somatic chromosomes: Control physical
characteristics. There are twenty-two pairs of somatic chromosomes. A
pair of identical chromosomes forms a homologous chromosome (one
inherited from each parent).
- Sex Chromosomes: Involved in sex determination. They are X chromosome and Y chromosome.
- The Y chromosome is comparatively smaller than the X chromosome.
- The SRY gene on the Y chromosome is responsible for the development of testis in the embryo.
- Normal Genetic Constitution: Female: 44 + XX; Male: 44 + XY.
- Variant Genetic Constitutions: Examples include
Turner syndrome (44+X0), Triple-X syndrome (44+XXX), Klinefelter
syndrome (44+XXY), and XYY syndrome (44+XYY). These influence physical
and mental development.
IV. Genes and Protein Synthesis
- Gene: A gene is a specific sequence of nucleotides
in DNA. Proteins are synthesized according to gene instructions and are
responsible for forming characteristics and controlling metabolic
activities.
- RNA (Ribonucleic acid): Another type of nucleic acid involved in protein synthesis.
- It is made up of nucleotides containing a ribose sugar, a phosphate
group, and nitrogenous bases (Adenine, Guanine, Uracil, and Cytosine).
- Most RNAs have a single strand.
- Stages of Protein Synthesis:
- Transcription: mRNA (messenger RNA) is formed from a
specific nucleotide sequence (gene) in DNA, carrying messages for
protein synthesis. This process takes place in the nucleus.
- Translation: tRNAs (transfer RNA) carry specific
amino acids to the ribosome. rRNAs (ribosomal RNA), which are part of
the ribosomes, combine amino acids to make protein. This process takes
place in the cytoplasm.
V. Principles of Inheritance (Mendel)
- Heredity: The transmission of characteristics from parents to offspring.
- Variations: Characters expressed in offspring that differ from their parents.
- Genetics: The branch of science dealing with genes, heredity, and variation.
- Gregor Johann Mendel (Father of Genetics) laid the
foundation for the field through experiments on pea plants (Pisum
sativum). His conclusions are known as the Laws of Inheritance.
- Terminology:
- Factors: Hypothetical units (now known as genes) transmitted through gametes that determine a character.
- Alleles: Different forms of a gene.
- Phenotype: The observable characteristics of an organism.
- Genotype: The genetic constitution responsible for the characteristics.
- Monohybrid Cross (Single Trait):
- Inference: When a pair of contrasting traits is
hybridised, only one (the dominant trait) is expressed in the first
generation (F1), while the other (recessive trait) remains hidden. The
hidden trait reappears in the second generation (F2).
- Law of Segregation: When gametes are formed, the factors (alleles) that determine the trait get separated without mixing.
- The ratio of dominant to recessive traits in the F2 generation is 3:1.
- Dihybrid Cross (Two Traits):
- Mendel’s Postulate (Law of Independent Assortment):
When two or more different traits are combined, each trait is inherited
independently to the next generation without mixing; one pair of
alleles does not influence the separation of another pair.
VI. Non-Mendelian Inheritance and Variation Sources
- Non-Mendelian Inheritance: Explains traits
resulting from complex interactions among genes, environment, and other
factors, limiting the explanation provided solely by Mendel’s laws.
- Incomplete Dominance: A dominant allele cannot
fully hide the recessive allele. The offspring expresses a character
intermediate to the parents (e.g., pink flowers from red x white).
- Co-dominance: Both alleles exhibit their traits at
the same time. The F1 generation shows similarity with both parents
(e.g., Roan coat pattern, ABO blood group).
- Multiple Allelism: The gene that determines a character has more than two alleles (e.g., ABO blood group determined by IA, IB, and i).
- Polygenic Inheritance: More than one gene controls the character (e.g., difference in skin colour).
- Genetic Processes Responsible for Variations:
- Crossing Over: Occurs during the first phase of
meiosis. Homologous chromosomes pair up. Chromatids break at the point
of contact (chiasma) and exchange segments, causing a recombination of
alleles. This leads to the appearance of new traits in the offspring.
- Mutation: A sudden, heritable change in the genetic
constitution of an organism. It can be caused by errors during DNA
replication, exposure to certain chemicals, or radiations. Mutations
change genes, are transferred through generations, and play a crucial
role in evolution.
Chapter 2: Paths of Evolution
I. Evolution and Early Theories
- Antibiotic Resistance: Resistance in bacteria
(e.g., tuberculosis bacteria) is caused by a mutation in a specific
gene. The mutated bacteria multiply even in the presence of antibiotics.
Over time, through further mutations, they acquire the ability to
resist multiple antibiotics, leading to multi-drug-resistant strains
(superbugs).
- Lamarckism (Theory of Inheritance of Acquired Characters): Initiated by Jean Baptiste Lamarck.
- Idea: Organisms adapt to changes, and characters
acquired during their lifetime (e.g., giraffe stretching its neck to
reach high leaves) are transmitted through generations, leading to the
emergence of new species.
- Limitation: Later scientists proved that acquired
characters do not impart change in the genetic structure of organisms
and are thus not inherited.
- Darwinism (The Theory of Natural Selection):
Proposed by English naturalist Charles Darwin. It marked the foundation
for modern evolutionary perspectives and was published in On the Origin of Species (1859).
- Key Concepts of Natural Selection:
- Over Production: Organisms produce more offspring than the environment can support.
- Variations: Organisms exhibit differences (size, immunity, etc.) that can be favourable or harmful.
- Struggle for existence: Competition among organisms due to limited resources (food, shelter, mates).
- Survival of the fittest: Organisms with favourable variations survive the struggle, reproduce more effectively, and produce new generations.
- Natural Selection: Favourable variations are passed
on and accumulate over time, leading to the creation of new species
that cannot reproduce within the original species.
- Neo Darwinism: A rationalised theory developed
after incorporating discoveries of Gregor Mendel and concepts of
chromosomes and genes. It recognized that the causes of variation are
genetic changes, genetic recombination during sexual reproduction, and
gene flow.
II. Speciation and Evidences of Evolution
- Speciation: The process in which new species arise from a common ancestor.
- LUCA (Last Universal Common Ancestor): Thought to be the ancestor of all species.
- MRCA (Most Recent Common Ancestor): The ancestor shared by different species.
- Speciation occurs when members of a population become isolated (by
ecological or other factors like mutation/natural selection), accumulate
variations over time, and eventually become unable to reproduce
mutually.
- Evidences of Evolution:
- Molecular Biology: Comparing the sequence of
nucleotides in DNA or amino acids in proteins. For example, the beta
chain of haemoglobin shows 0 difference between humans and chimpanzees,
suggesting the closest evolutionary relationship.
- Comparative Anatomy: Similarities in the internal
structure of different organisms validate evolution. Homologous
structures, like the forelimbs of humans, cats, whales, and bats, are
similar internally but differ in external structure and function.
- Fossil Evidences: Remains or traces of ancient
organisms. They show that organic evolution is a gradual process (e.g.,
ancestors of horses had shorter legs) and reveal connecting links (e.g.,
Archaeopteryx possessing features of both reptiles and birds).
III. Human Evolution
- Primate Characteristics: Humans, monkeys, and apes
belong to the group of primates. Common features include a thumb that
can be opposed to other fingers and binocular vision.
- Evolutionary Trend: A major trend in human
evolution is the increase in brain capacity, which nearly tripled over
two million years. This enabled complex social behaviour, tool making,
language use, and higher-level cognitive functions.
- Key Ancestors (with Cranial Capacity):
- Sahelanthropus tchadensis (350 cm³): First link in human evolutionary series.
- Astralopethecus (450 cm³): Skeletal structure confirms bipedalism (walking on two legs).
- Homo habilis (600 cm³): Made tools with stones using hands....
- Homo erectus (900 cm³): Able to walk upright on two legs; used excellent stone weapons....
- Homo neanderthalensis (1450 cm³): Contemporaries of modern man; buried dead bodies....
- Homo sapiens (1350 cm³): Modern man; acquired technology, agriculture, built cities.
IV. The Nervous System
- Role: The nervous system controls and coordinates the vital functions of the body.
- Components: Brain, spinal cord, nerves, and receptors.
- Neuron (Nerve Cells): Basic building blocks; specialised cells capable of receiving stimuli and forming messages.
- Cell body (Cyton): Center of the neuron.
- Dendrites/Dendrons: Fine fibres/branches that receive messages from adjacent neurons and transmit them to the cyton.
- Axon: The longest fibre from the cell body.
- Axonites: Branches of the axon.
- Synaptic knob: Knob-like structure at the tip of the axonite; contains a neurotransmitter (e.g., Acetylcholine) to transfer chemical messages.
- Neuroglial cells: More than half of the brain and
spinal cord cells. They cannot receive stimuli or transmit messages.
Functions include bringing nutrition, eliminating wastes, and acting as
defence cells.
- Myelin Sheath: A layer covering some axons, made up of shiny white fat (Myelin).
- Functions: Increases the speed of message transmission (acts as an insulator), provides nourishment, and protects the axon.
- Formation: Produced by oligodendrocytes (in brain/spinal cord) and Schwann cells (in nerves).
- Matter: White matter is where myelinated neurons
are abundant; grey matter is where cell bodies and parts without myelin
sheath are seen.
- Protection of CNS (Brain and Spinal Cord):
- Covered by the three-layered Meninges.
- Cerebrospinal Fluid (CSF): Fills the space between
the inner membranes of the meninges, the brain cavities, and the central
canal of the spinal cord. Functions include providing oxygen/nutrients,
eliminating wastes, regulating pressure, and protecting from external
injuries.
- Divisions of Nervous System:
- Central Nervous System (CNS): Includes the Brain and Spinal cord.
- Peripheral Nervous System (PNS): Includes 12 pairs of cranial nerves and 31 pairs of spinal nerves, receptors, and nerve ganglia.
- Brain Functions:
- Cerebrum: Largest part. Centre of memory, intelligence, thinking, imagination, and voluntary movements.
- Cerebellum: Second largest part; maintains equilibrium by coordinating muscular activities.
- Thalamus: Acts as the relay station of messages to and from the cerebrum.
- Hypothalamus: Helps in maintaining homeostasis by regulating body temperature, hunger, thirst, and emotions.
- Medulla Oblongata: Controls involuntary activities like heartbeat, ventilation, vomiting, cough, and sneezing.
- Nerve Impulse Transmission: Messages are transmitted as nerve impulses.
- Unstimulated neuron: Outer surface is positively charged; inner surface is negatively charged.
- Stimulation: Positive ions enter the cell, causing a temporary charge variation.
- Synapse: The part where an impulse is transferred from one neuron to another.
- The synaptic knob secretes neurotransmitters into the synaptic cleft
(gap), which bind to the receptors of the post-synaptic membrane,
stimulating the next neuron.
- Synapses transmit impulses in only one direction and increase their speed.
- Neocortex: The complex, six-layered cerebral
cortex, highly developed in humans. Its synapses enable advanced mental
processes like thinking and decision-making.
- Types of Neurons (by function):
- Sensory neuron: Transmits impulses from receptors to CNS.
- Motor neuron: Transmits instructions from CNS to organs (muscles/glands).
- Inter neuron: Found between neurons, helping in central processing.
- Autonomous Nervous System (ANS): Part of the PNS that regulates body activities by itself.
- Sympathetic system: Prepares 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, decreases heartbeat, stimulates digestion).
- Reflex Actions: Reactions that occur spontaneously
and involuntarily in response to stimuli. They can originate from the
spinal cord or the brain.
- Reflex Arc: The pathway through which impulses are
transmitted: Receptor → Sensory neuron → Inter neuron (often in spinal
cord) → Motor neuron → Muscle/Gland.
Chapter 3: Behind Sensations
I. Stimuli, Receptors, and Senses
- Stimuli: Circumstances that lead to responses in living beings (external or internal).
- Sensory Receptors: Specialised cells or nerve endings that recognise stimuli.
- Impulse Formation: Stimuli cause electrical impulses called Receptor potential. If the concentration of these impulses is high, Action potential is formed in the associated neurons, which travels as a nerve impulse.
- Types of Senses:
- General Senses: Detected by receptors in skin, muscles, joints, internal organs (e.g., touch, pain, heat, pressure).
- Special Senses: Detected by receptors concentrated only in certain organs (e.g., vision, hearing, taste, smell).
II. Vision (The Eye)
- Protective Mechanisms: Eyelid, eyelashes, tears. Tears are produced by lacrimal glands and contain the enzyme lysozyme to protect from infections.
- Conjunctiva: A membrane covering the anterior part of the eye (except cornea); keeps it moist and lubricated.
- Layers of the Eye:
- Sclera (Outer Layer): Provides firmness and protection.
- Choroid (Middle Layer): Provides oxygen and nutrients to the retina; regulates temperature. Contains the Iris.
- Retina (Inner Layer): Contains photoreceptor cells; where the image is formed.
- Associated Parts:
- Cornea: Transparent anterior part; allows light to enter.
- Iris: Contains melanin pigment; regulates the amount of light entering the eye by adjusting the size of the Pupil (the aperture at its centre)....
- Lens: A convex lens that forms a small, real, and inverted image on the retina. Attached to Ciliary muscles by ligaments.
- Power of Accommodation: The ability of the eye to
focus images of both near and distant objects accurately on the retina
by changing the curvature of the lens.
- Eye Chambers and Humors:
- Aqueous chamber: Between cornea and lens; contains watery Aqueous humor (provides O₂/nutrients to lens/cornea, regulates pressure).
- Vitreous chamber: Between lens and retina; contains jelly-like Vitreous humor (maintains the shape of the eyeball).
- Photoreceptors (in Retina): Both types contain pigments composed of opsin and retinal (formed from Vitamin A).
- Rod Cells: More numerous (9+ crores); contain Rhodopsin. Recognise objects in dim light and shades of black and white.
- Cone Cells: Less numerous (45 lakh); contain Photopsin. Provide vision in intense light and help recognise colours.
- Vision Centre: The yellow spot (macula) is where cone cells are abundant. The blind spot is where the optic nerve originates, lacking photoreceptors.
- Impulse Transmission: In the dark, photoreceptors continuously produce the neurotransmitter Glutamate.
In the presence of light, glutamate production stops, activating 'on
bipolar cells' which send impulses via ganglion cells to the optic
nerve.
- Binocular Fusion: The brain compares the two
slightly different images received from both eyes and combines them,
resulting in 3D vision and depth perception.
- Disorders: Short-sightedness (enlarged eyeball),
Cataract (opaque lens), Glaucoma (increased pressure due to failure of
aqueous humor reabsorption), Night blindness (Vitamin A deficiency).
III. Hearing and Balance (The Ear)
- Main Parts: Outer ear, Middle ear, Inner ear.
- Outer Ear: Pinna (directs sound waves) and Auditory canal (protects tympanum, contains hair/wax).
- Middle Ear: Tympanum (eardrum) vibrates with sound. Ear ossicles (Malleus, Incus, Stapes) transmit vibrations. Eustachian canal connects to the pharynx and balances air pressure on both sides of the tympanum.
- Inner Ear: Includes the Cochlea (hearing) and the Vestibular system (balance).
- Mechanism of Hearing:
- Vibrations travel from the tympanum → ear ossicles → oval window.
- Cochlea: Snail-shaped, has three chambers. Upper/lower chambers contain Perilymph; middle chamber contains Endolymph.
- Organ of Corti: Located in the basilar membrane.
Contains auditory receptors (hair cells) that generate impulses when
vibrated. Impulses reach the brain through the auditory nerve.
- Mechanism of Balance:
- Involves the vestibular system in the inner ear: three semicircular canals and the vestibule (containing utricle and saccule).
- Endolymph moves with head rotation, stimulating hair cells in the canals and vestibule.
- Impulses travel through the vestibular nerve to the brain (cerebellum).
- Hearing Impairment: Caused by noise intensity above
80 decibels; loud noise (>85 dB) for a short time or less intense
noise (<55 dB) for a very long time can cause permanent impairment.
IV. Smell, Taste, and Touch
- Olfaction (Smell):
- Particles responsible for smell dissolve in the mucus produced by the mucus membrane in the nasal cavity.
- Millions of olfactory neurons (receptors) get stimulated.
- Impulses travel through the olfactory nerve to the brain.
- Taste:
- Detected by Chemoreceptors located in Taste buds, which are found in the Papilla of the tongue.
- Substances dissolve in saliva and stimulate the chemoreceptors.
- Main tastes recognised: sweet, sour, salty, pungent, bitter, and umami.
- Skin Receptors (Touch/Pain): The skin contains various specialised receptors.
- Nocireceptors (Independent nerve endings): Specialised receptors that identify pain.
- Merkel disc/Meissner corpuscles: Detect touch and pressure.
- Pacinian corpuscles: Detect vibration and high-frequency touch.
Chapter 4: Chemoreception in Organisms
I. Hormones and General Function
- Definition: Hormones are chemical substances that regulate and coordinate body functions alongside the nervous system.
- Target Cells: A cell in which a hormone acts. Each target cell has receptors suitable for that hormone.
- Mechanism: Hormones combine with receptors to form a hormone-receptor complex, which controls activities inside the cell.
- Transport: Animal hormones (from endocrine glands)
reach target cells through the blood. Plant hormones move via
cell-to-cell transport or through xylem/phloem.
II. Plant Hormones
- Auxin: Discovered by F W Went. Stimulates cell
elongation, increases stem length, inhibits lateral bud growth, and
regulates tropic movements. Tends to stay away from light, causing
bending (phototropism).
- Gibberellins: Break seed dormancy; influence fruit and seed growth; stimulate cell division in stems and roots.
- Cytokinins: Stimulate cell division and
differentiation; stimulate lateral bud growth; delay senescence and
retain the green colour of leaves.
- Ethylene: Plays a role in the ageing of leaves/flowers and the ripening of fruits.
- Abscisic Acid (ABA): Inhibits the growth of plant
parts; maintains seed dormancy until favourable conditions arise;
enables plants to tide over unfavourable conditions.
- Photoperiodism: The response of plants to the duration of day and night, regulating flowering time. Involves Phytochrome, a light-sensitive pigment synthesized in fully developed leaves.
III. Regulation in Humans
- Thyroid Gland (Metabolism):
- Thyroxine (from Follicular cells): Controls
metabolism, body temperature, brain development in children, and
maintains health of heart/skin/reproductive system.
- Calcitonin (from Parafollicular cells): Reduces the level of calcium in the blood.
- Disorders: Hyperthyroidism (excessive thyroxine), Hypothyroidism (reduced thyroxine), and Goitre (swelling in the neck).
- Regulation of Calcium (Normal: 9-11 mg/dL): Maintained by the combined action of Calcitonin and Parathormone (from the parathyroid gland).
- When calcium is high, Calcitonin inhibits its release from bones.
- When calcium is low, Parathormone stimulates its release from bones and increases reabsorption from the blood.
- Pancreas (Glucose Regulation):
- Islets of Langerhans: Contain Alpha cells (produce Glucagon) and Beta cells (produce Insulin).
- Insulin Action (when glucose level increases): Speeds up glucose entry into cells; promotes glucose → glycogen conversion in the liver.
- Glucagon Action (when glucose level decreases):
Promotes glycogen → glucose conversion in the liver; promotes glucose
synthesis from amino acids.
- Diabetes Mellitus: Blood glucose level rises above normal (FBS > 126 mg/dL). Type 1 (loss of insulin production due to beta cell destruction). Type 2 (variation in insulin production or decreased effectiveness).
- Adrenal Gland (Emergency): Works with the sympathetic nervous system.
- Medulla: Secretes Epinephrine (adrenaline) and Norepinephrine. These increase heart rate/blood pressure/blood glucose, preparing the body for emergency.
- Cortex: Produces corticosteroids (Glucocorticoids like Cortisol, Mineralocorticoids like Aldosterone, and Gonadocorticoids).
- Cortisol resists inflammation, suppresses immune responses, and maintains glucose homeostasis.
- Pineal Gland (Sleep): Produces Melatonin. Variations in secretion influence sleep and wakefulness; the gland is known as the biological clock.
- Hypothalamus and Pituitary (Master Control):
- Hypothalamus: Master controller. Controls pituitary function by producing Releasing and Inhibitory hormones that regulate tropic hormone production in the anterior lobe.
- Pituitary Anterior Lobe: Secretes tropic hormones (TSH, ACTH, GTH) and Somatotropin (GH) (growth hormone).
- Pituitary Posterior Lobe: Stores and secretes Vasopressin (ADH) (water reabsorption in kidney) and Oxytocin (smooth muscle contraction, lactation).
- Growth Disorders: Caused by Somatotropin variations. Dwarfism (decreased GH during growth phase), Gigantism (increased GH during growth phase), Acromegaly (increased GH after growth phase).
- Pheromones: Chemical substances secreted by
organisms into the surroundings for communication with the same species.
Examples include: Territorial, Aggregation, Alarm, Trail, and Sex
pheromones.
Chapter 5: Immunity and Healthcare
I. Immunity Mechanisms
- Health: A complete state of physical, mental, and social well-being.
- Antigen: Anything (pathogens, pollen, chemicals) that enters the body and causes disease.
- Immunity: The body's ability to prevent the entry of pathogens and destroy those already inside.
- Innate Immunity (Non-specific): Natural, present by birth, acts irrespective of the type of pathogen.
- Primary Level: Physical and chemical barriers (e.g., Lysozyme in tears/saliva, Mucus membrane, HCl in stomach, Wax in ear).
- Secondary Level: Defence mechanisms if pathogens enter:
- Phagocytosis: Phagocytes (e.g., Neutrophils and Monocytes) engulf and destroy pathogens.
- Inflammatory Response: Blood vessels dilate due to histamine release; increased blood flow brings white blood cells to the injured area.
- Fever: Increased body temperature (above 98.6°F) triggered by pyrogens. It enhances phagocytosis and inhibits pathogen growth.
- Blood Clotting: Prevents blood loss and blocks
pathogen entry. Involves thromboplastin converting prothrombin to
thrombin, and thrombin converting fibrinogen to fibrin threads.
- Acquired Immunity (Specific): Develops after birth; specifically recognises antigens. Carried out by Lymphocytes.
- T Lymphocytes: Form in bone marrow, mature in the thymus gland. Destroy infected cells and cancer cells.
- B Lymphocytes: Form and mature in the bone marrow. Produce proteins called antibodies.
- Artificial Immunity (Vaccination): Immunisation is an artificial method to prepare immune cells.
- Vaccines: Act as antigens, stimulating the immune
system to produce antibodies for long-term protection. Edward Jenner is
known as the father of vaccination.
II. Diseases and Pathogens
- Acquired Diseases: Occur during life (communicable or non-communicable).
- Transmission: Direct contact, contaminated food/water, surfaces, coughing/sneezing (droplets).
- Bacterial Diseases: Bacteria release toxins or
enzymes that destroy host tissues. Examples: Rat fever (Leptospira),
Tuberculosis (Mycobacterium tuberculosis).
- Viral Diseases: Viruses multiply using the host
cell's genetic mechanism, destroying the cells. Examples: AIDS (HIV
attacks T lymphocytes, reducing immunity), Nipah.
- Fungal Diseases: Fungi infect skin/nails or produce toxins. Examples: Ringworm, Candidiasis.
- Protozoan Diseases: Unicellular eukaryotes.
Example: Malaria (Plasmodium, transmitted by Anopheles mosquito,
destroys red blood cells). Amoebic encephalitis (Naegleria fowleri).
- Worm Infestations: Caused by parasitic worms (e.g.,
pin worm, round worm). Filariasis is caused by filarial worms
transmitted by Culex mosquitoes, which lodge in lymphatic vessels and
cause swelling.
- Non-Contagious Diseases:
- Cancer: Abnormal and uncontrolled cell division.
Normal cells turn into cancer cells when control mechanisms fail,
spreading through blood/lymph.
- Hereditary Diseases (Genetic Defects): Sickle cell
anaemia (defective gene for haemoglobin, causes sickle-shaped RBCs).
Haemophilia (defective gene for blood clotting proteins).
III. Healthcare and Blood
- Treatment Systems: Ayurveda (traditional Indian system, focus on balance, diet, herbs). Homeopathy (uses diluted doses of natural substances). Modern Medicine (focus on diagnosis, pathogens, surgery, organ transplantation).
- Antibiotics: Medicines used against bacteria,
derived from microorganisms or synthesized. Revolutionary (Penicillin
discovered by Alexander Fleming, 1928). Excessive use leads to side
effects and Antibiotic resistance.
- Blood Groups: Determined by the presence of A antigen and B antigen on the surface of RBCs.
- Rh factor: Determined by the presence (positive) or absence (negative) of the D antigen.
- Blood group matching is essential for transfusion because antibodies
in the recipient's plasma may act against donor antigens, causing
agglutination.
Chapter 6: Biology and Technology
I. Genetic Engineering Technologies
- Biotechnology: Technology using living things or their parts to provide useful products and services for humans.
- Genetic Engineering: Technology used for creating desired traits in organisms by combining or deleting genes.
- Recombinant DNA Technology: Combines DNA segments from two or more different organisms. Requires:
- Restriction Endonuclease Enzyme: Acts as genetic scissors, cutting specific genes.
- Ligase Enzyme: Acts as genetic glue, joining DNA segments.
- Vector: Carries genes (e.g., bacterial plasmids or some viruses).
- Host Cell: Where the recombinant DNA is inserted and becomes active (e.g., production of human insulin using bacteria).
- CRISPR Technology (Gene Editing): Modern technology used to edit DNA with great precision.
- Uses Cas9 enzyme as scissors to cut DNA.
- Uses a Guide RNA (gRNA) that precisely identifies the DNA segment to be cut.
- Allows removal of unwanted characteristics or addition of 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 (insulin
production).
II. Genomics and Gene Therapy
- Genome: The sum total of all the genetic materials in an organism.
- Human Genome Project (HGP): A global initiative (1990–2003) to sequence and understand the human genome (approximately 300 crore DNA base pairs). It used Gene Mapping to identify gene locations.
- HGP Findings: Humans have 20,000 to 25,000 genes; only 1–2% of the genome consists of functional genes.
- Gene Therapy: The method of treating diseases by removing defective genes and replacing them with functional genes.
- Somatic gene therapy: Delivers healthy genes to body cells; genetic changes are not passed on to the next generation.
- Germline gene therapy: Transfers genes into reproductive cells; genetic changes are transmitted to future generations (raises ethical questions).
- DNA Fingerprinting: Discovered by Sir Alex Jeffrey (1984).
- Basis: While 99.9% of DNA is the same, variations
in the remaining 0.1% (especially in repeated sequences in non-coding
regions) are unique to each individual.
- Uses: To identify culprits, determine biological
relationships (parents/offspring), identify genetic disorders, and track
endangered species.
III. Modern Biology and Environmental Technology
- Human Microbiome Project (HMP): Launched in 2007,
studying the collection of microorganisms (bacteria, fungi, viruses) and
their genes that inhabit the human body. This community provides
services like immunity, digestion, and vitamin production.
- Faeces to Medicine: Beneficial bacteria collected from healthy faeces ("poop pills") are used to treat drug-resistant bacterial infections.
- Biology and Artificial Intelligence (AI): AI plays a major role in biological study.
- Applications: Diagnosis, drug discovery,
personalised medicine (analysing genetic makeup), improving agriculture
(monitoring soil/predicting crop diseases), pollution prediction, and
genome sequencing.
- Bioinformatics: A scientific discipline that
analyses large amounts of biological data by combining computer science,
mathematics, and statistics.
- Technologies for Environmental Conservation:
- Cryopreservation: Preserving living cells/tissues at very low temperatures (-196°C) for long-term preservation.
- Bioremediation: Uses microorganisms and plants to remove pollutants from contaminated environments.
- Wildlife Tracking/Data Sensors: Utilising sensors and satellite remote sensing to monitor biodiversity and animal movement for conservation planning.
