Chapter 1: Genetics of Life

Question 1: Are basic building blocks of DNA and RNA the same? Explain.
Answer: The basic building blocks, called nucleotides, are not entirely the same.

• A DNA nucleotide is composed of a deoxyribose sugar, a phosphate group, and a nitrogen base (Adenine, Thymine, Guanine, or Cytosine).
• An RNA nucleotide is composed of a ribose sugar, a phosphate group, and a nitrogenous base (Adenine, Uracil, Guanine, or Cytosine).
• While both share the phosphate group, they differ in two components: DNA uses deoxyribose sugar, whereas RNA uses ribose sugar; and DNA uses Thymine, whereas RNA uses Uracil.

Question 2: Analyse the statements and choose the appropriate one.
i. F1 has similarity with both the parents.
ii. F1 has no similarity with any of the parents’ character intermediate to them.
iii. F1 has similarity with one of the parents
Answer: c) i - Co-dominance, ii - Incomplete dominance, iii - Dominance.

• Co-dominance (i): Both alleles exhibit their traits at the same time (e.g., Roan coat pattern).
• Incomplete Dominance (ii): The dominant allele cannot fully hide the recessive allele, resulting in an intermediate trait.
• Dominance (iii): When contrasting traits are hybridised, only one trait (the dominant one) is expressed in the F1 generation.

Question 3: Which of the following is contributed by organisms that reproduce sexually, to their offspring?
a) All genes
b) Half of their genes
c) One fourth of their genes
d) Double the number of genes
Answer: b) Half of their genes.

• A pair of chromosomes forms a homologous chromosome, with one inherited from the mother and the other from the father. Sexual reproduction involves the transmission of factors (genes) through gametes, each gamete carrying half the genetic constitution.

Question 4 (Abridged): A tall pea plant with purple flowers (dominant character) is crossed with a dwarf plant with white flowers.
b) Did characters that differ from the parents appear in the F2 generation? Why?
Answer: Yes, characters that differed from the parental plants (e.g., tall with white flowers, dwarf with purple flowers) appeared in the F2 generation. This occurs because when two or more different traits are combined, each trait is inherited independently to the next generation without mixing.

Question 5: How does dominance, co-dominance and incomplete dominance differ from one another?
Answer: These inheritance patterns differ based on how the traits are expressed in the hybrid (F1) generation:

• Dominance: Only the dominant trait is expressed in the F1 generation, and the recessive trait remains hidden.
• Incomplete Dominance: The F1 offspring express a trait that is intermediate to the parents because the dominant allele cannot fully hide the recessive allele (e.g., red and white flowers yielding pink flowers).
• Co-dominance: Both alleles exhibit their traits at the same time in the F1 offspring (e.g., the Roan coat pattern in cattle).

Question 7: Even though a gene responsible for certain characters has more than two alleles, why does that particular gene have only two alleles in an individual?
Answer: While a gene may exhibit Multiple Allelism (meaning the gene pool of the human population, for example, has more than two alleles, such as Iᴬ, Iᴮ, and i for blood group determination), an individual organism inherits only two alleles for that character, one from each parent.

Question 8: Although the DNA possesses all genetic information for protein synthesis, RNA is also required for protein synthesis. Why?
Answer: RNA is crucial because the process of protein synthesis involves multiple steps requiring different types of RNA:

1. Transcription: Messenger RNA (mRNA) is formed from the specific gene sequence in the DNA (which is in the nucleus).
2. Translation: The mRNA travels to the ribosome (in the cytoplasm). Transfer RNA (tRNA) carries specific amino acids to the ribosome based on the message in the mRNA. Ribosomal RNA (rRNA), which is part of ribosomes, combines these amino acids to make the protein.

Question 9: How do co-dominance and multiple allelism function in the determination of blood group in the ABO blood grouping in human beings? Explain.
Answer:

• Multiple Allelism: The gene that determines blood group in human beings has more than two alleles (specifically three alleles: Iᴬ, Iᴮ, and i).
• Co-dominance: This occurs when the alleles Iᴬ and Iᴮ are inherited together. Both alleles express their traits simultaneously, resulting in the AB blood group.

Question 10: All ova formed in females contain one type of sex determining chromosome. Why?
Answer: The normal genetic constitution for a female is 44 + XX. When gametes (ova) are formed through meiosis, the pair of factors (sex chromosomes) separate. Since both sex chromosomes are identical (X and X), every ovum produced will contain only one type of sex chromosome: the X chromosome.

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Chapter 2: Paths of Evolution

Question 2: Although dolphins have a larger brain than that of humans, the level of thinking, language skills and social relationships are higher in humans. Evaluate this statement based on the following indicators:

• Difference in the structure of the brain
• Influence of natural selection
  Answer:
• Difference in the structure of the brain: Human superiority in complex thinking is attributed to the neocortex, the cerebral cortex of the brain. In mammals, the cerebral cortex is modified into a complex, six-layered neocortex, which is more developed in humans compared to other mammals. The neocortex facilitates advanced mental processes like thinking, decision-making, learning, recalling, and social interaction.
• Influence of Natural Selection: The increase in brain capacity (which nearly tripled over two million years) is a major trend in human evolution. This development facilitated complex social behaviour, the ability to make tools, use language, and perform higher-level cognitive functions. This enhanced ability to adapt to changing environments and develop culture and advanced technologies was naturally selected, laying the foundation for the transition to Homo sapiens.

Question 3: Redraw the figure of the neuron and label the following parts by writing their names.
(a) The part of the neuron that receives impulses from the adjacent neuron
(b) Part that contains neurotransmitter
(c) Part that acts as insulator
Answer:
(a) The part of the neuron that receives impulses from the adjacent neuron is the Dendrites (branches of the Dendrons).
(b) The part that contains neurotransmitter is the Synaptic knob (seen at the tip of the axonite).
(c) The part that acts as an insulator is the Myelin sheath (which is made up of a shiny white fat and increases the speed of transmission of messages).

Question 4: Darwin failed to explain the reasons of variation even though he argued that variations occur continuously in organisms. Evaluate this statement based on the findings of Neo Darwinism.
Answer: The statement is valid as Charles Darwin did not have knowledge regarding the genetic basis of variations and inheritance. Neo Darwinism addressed this limitation by incorporating later discoveries, such as those made by Gregor Mendel, about chromosomes and genes. Neo Darwinism recognizes that the causes of variations that lead to evolution are genetic changes (mutations), genetic recombination during sexual reproduction, and gene flow.

Question 5: Observe the illustration and answer the questions. (Illustration shows Central Nervous System (A) connected to body parts via nerves (B)).
(a) Identify the nerves A and B.
Answer: A: Central Nervous System (Includes Brain and Spinal Cord). B: Peripheral Nervous System (Includes cranial nerves, spinal nerves, receptors, and nerve ganglia that connect the central nervous system to the organs).
(b) Are messages being exchanged between A and B? Explain.
Answer: Yes, messages are continuously exchanged between the Central Nervous System (A) and the Peripheral Nervous System (B). The spinal cord (part of A) transmits messages from different parts of the body (via B) to the brain, and transmits instructions from the brain (via A) to different parts of the body (via B).

Question 6: A table that includes the parts of spinal cord and their functions is given below. Arrange column B appropriately in accordance with column A of the table.

A. Part	B. Functions/ Peculiarities
Central canal	Fluid present here nourishes the spinal cord
White matter	Neurons with myelin sheath are numerous
Dorsal root	Transmits impulses to the spinal cord (messages from the body)
Grey matter	Cell body of neurons are numerous (also parts of neurons without myelin sheath)

Question 7: Based on the information obtained from fossils, some human ancestors and their characteristics are given below. Find out the one which is arranged correctly from the given answers.
(A) Homo habilis (i) buried dead bodies
(B) Homo neanderthalensis (ii) able to stand upright on two legs
(C) Australopithecus (iii) made tools with stones using their hands
(D) Homo erectus (iv) The skeletal structure confirms bipedalism
Answer: (b) A : iii, B : i, C : iv, D : ii....

• (A) Homo habilis (iii) made tools with stones using their hands.
• (B) Homo neanderthalensis (i) buried dead bodies.
• (C) Australopithecus (iv) The skeletal structure confirms bipedalism.
• (D) Homo erectus (ii) able to walk upright on two legs.

Question 9: Complete the table by including the following in appropriate columns.

• Only long necked giraffes survive
• Use and Disuse
• Natural selection
• Variations acquired in the life span
• Through continuous use, giraffe's neck elongates
• Inheritance of variations

Lamarckism	Darwinism
Use and Disuse	Natural selection
Variations acquired in the life span	Only long necked giraffes survive
Through continuous use, giraffe's neck elongates	Inheritance of variations

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Chapter 3: Behind Sensations

Question 1: Which of the following statements is correct?
a. Each taste bud has different chemoreceptors.
b. Opsin in rhodopsin contains retinal which is formed from vitamin A.
c. Photoreceptors are formed from optic nerve.
d. Both rhodopsin and photopsin contain retinal.
Answer: Both b) and d) are supported by the text.

• b) Opsin in rhodopsin contains retinal which is formed from vitamin A: The pigment rhodopsin (in rod cells) includes a protein (opsin) and retinal, which is formed from Vitamin A.
• d) Both rhodopsin and photopsin contain retinal: The components of both rod cell pigment (rhodopsin) and cone cell pigment (photopsin) include a protein (opsin) and retinal, formed from Vitamin A.

Question 5: Correct the mistake, if any. Impulses are formed in the retina due to the dissociation of rod cells.
Answer: The mistake is that the formation of impulses is more directly related to chemical changes, not just dissociation. Impulses are formed in the retina due to variations in glutamate production (the primary neurotransmitter in photoreceptors), which is controlled by the presence or absence of light.

Question 6: Analyse the given word pairs below, and find the relationship between them.

• Retinal - Night blindness
• Umami - Taste buds
• Cone cells - Colour Blindness
  Answer:
• Retinal - Night blindness: Retinal is formed from Vitamin A. Night blindness is a condition caused by the deficiency of Vitamin A.
• Umami - Taste buds: Umami is one of the main tastes recognized. Taste buds contain the chemoreceptors responsible for sensing taste.
• Cone cells - Colour Blindness: Cone cells provide vision in intense light and help in recognising colours. Colour blindness is caused by defects in the genes responsible for the production of pigments in cone cells.

Question 8: Which part of the eye helps in focusing the light towards the retina
a) Cornea
b) Pupil
c) Lens
d) Iris
Answer: c) Lens.

• The convex lens forms a small, real, and inverted image of the object accurately on the retina. The eye adjusts the curvature of the lens to achieve the power of accommodation (focusing near/distant objects).

Question 9: What is the main function of a neuron?
a) Protects organs
b) Exchange electric signals
c) Filters blood
d) Produce retinalin
Answer: b) Exchange electric signals.

• Neurons (nerve cells) are specialized cells capable of receiving stimuli and forming suitable messages (nerve impulses), which are electrical signals/charges.

Question 10: How does the arrangement of rod cells and cone cells in the retina affect our ability to see in different conditions of light? Why does this adaptation become beneficial evolutionary?
Answer:

• Ability to See: The retina contains two types of photoreceptors:
  • Rod cells: Are numerous (over 9 crores) and contain rhodopsin. They recognize objects in dim light and in shades of black and white.
  • Cone cells: Are fewer (about 45 lakhs) and contain photopsin. They provide vision in intense light and help in recognizing colours.
• Evolutionary Benefit: This arrangement ensures that the organism can perceive the environment effectively across a wide range of light conditions, enabling both nocturnal and daylight activity, which is crucial for survival and adaptation.

Question 11: How does the structure of the ear enable it to convert the sound waves into signals that the brain can interpret? How do damages in different parts of the ear affect hearing and balance?
Answer:

• Conversion of Sound Waves: Sound waves are directed by the pinna into the auditory canal and vibrate the tympanum (eardrum). These vibrations are amplified and transmitted through the ear ossicles (malleus, incus, stapes) to the oval window. The oval window transmits vibrations to the fluids (perilymph and endolymph) within the cochlea. The fluid movement stimulates the hair cells located in the Organ of Corti (on the basilar membrane), generating impulses. These impulses travel through the auditory nerve to the brain, resulting in the sense of hearing.
• Effect of Damages:
  • Hearing: Damage to the tympanum, ear ossicles, oval window, or the structures within the cochlea (Organ of Corti, hair cells) would impair the transmission or generation of impulses, affecting hearing.
  • Balance: The vestibular system (including three semicircular canals, utricle, and saccule in the vestibule) is responsible for maintaining body balance. Damage here would inhibit the formation of impulses related to the head's linear or rotational movement, thereby impairing balance.

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Chapter 4: Chemoreception in Organisms

Question 1 (Abridged): The illustration related to the transmission of hormones to their target cells is given below. (A=Hormone, B=Receptor, C=Hormone-receptor complex).
i. Write the function of A with respect to the formation of C.
Answer: The hormone (A) combines with its receptor (B) to form the hormone-receptor complex (C). This complex then controls activities inside the cell.
ii. If A is the releasing hormone, where can B be found?
Answer: Releasing hormones (produced by the hypothalamus) stimulate the production of tropic hormones. Therefore, the receptor (B) for the releasing hormone (A) would be found on the target cells of the anterior lobe of the pituitary gland.
iii. How does the secretion and transmission of A differ in plants and animals?
Answer:

• Animals (Hormones): Produced by endocrine glands and transmitted to target cells through blood.
• Plants (Hormones): Produced at locations like the tip of the shoot or root, seeds, or sprouting leaves. They reach target cells via cell-to-cell transport or through xylem and phloem.

Question 2: The illustration given below is related to the regulation of calcium level in blood. (Normal 9 - 11 mg/dL. Decreases → Parathormone (Increases); Increases → ............(1)........... (Decreases))
(a) Which hormone is indicated as 1?
Answer: Calcitonin.

Question 4: Is it possible to sleep during the day just as one can sleep at night? Justify your opinion by relating it to the functions of the pineal gland.
Answer: While sleep is physiologically possible during the day, the quality of sleep is hormonally optimized at night. The pineal gland produces melatonin, the secretion of which influences sleep and wakefulness. Melatonin production increases in darkness (at night) and decreases during the day. Since darkness is necessary for melatonin to be produced in the required quantity for quality sleep, sleeping at night is generally better regulated by the body's natural biological clock.

Question 5: The hypothalamus functions as part of the nervous system and the endocrine system. Evaluate the statement.
Answer: The statement is correct.

• Nervous System Role: The hypothalamus is located in the brain, functioning to maintain homeostasis (e.g., regulating body temperature, hunger, thirst). It uses neurosecretory cells to produce hormones.
• Endocrine System Role: The hypothalamus is considered the master controller of the hormone production process. It controls the functioning of most endocrine glands by regulating the production of tropic hormones secreted by the anterior lobe of the pituitary gland.

Question 6: ‘A person runs very fast and escapes from a ferocious dog’. This incident involves the functions listed below. Write them in the correct sequence.

• Action of adrenal gland
• Action of the sympathetic nervous system
• Action of parasympathetic nervous system
  Answer:

1. Action of the sympathetic nervous system (equips the body to respond during emergency situations, leading to physical changes like increased heartbeat).
2. Action of the adrenal gland (medulla secretes epinephrine and norepinephrine, which prepare the body for emergency by increasing heart rate, blood pressure, and blood glucose).
3. Action of parasympathetic nervous system (prepares the body to relax and perform routine functions, which happens after the danger is averted).

Question 7 (Abridged): Information about a chemical substance is provided in the box:

• Organisms belonging to the same species secrete it into the surroundings for communication.
• It is used to mark a path and to attract mates.
  i) Which chemical substance is mentioned in the box?
  Answer: Pheromones.
  iii) How do farmers make use of this chemical substance?
  Answer: Farmers utilize pheromone traps for pest control in agricultural fields.

Question 8: X, Y, and Z are the functions of different plant hormones. X: Helps to tide over unfavourable situtation; Y: Delays senescence of leaves and retains the greenness in that; Z: Prevents the growth of the lateral bud. Choose the correct option.
i) Gibberellin, Ethylene, Abscisic acid
ii) Auxin, Abscisic acid, Gibberellin
iii) Abscisic acid, Cytokinin, Auxin
iv) Cytokinin, Gibberellin, Ethylene
Answer: iii) Abscisic acid, Cytokinin, Auxin.

• X (Unfavourable situation): Abscisic acid (ABA) inhibits growth and maintains seed dormancy until favourable conditions arise.
• Y (Delays senescence/retains greenness): Cytokinins delay senescence and retain the green colour of leaves.
• Z (Prevents lateral bud growth): Auxins inhibit lateral bud growth.

Question 9: Explain how the pancreas regulates the amount of glucose in the blood in the following situations.
Answer: The pancreas (Islets of Langerhans) regulates blood glucose using insulin (from beta cells) and glucagon (from alpha cells).

• A person eats carbohydrate-rich food: Blood glucose level increases. Insulin production increases, which speeds up the entry of glucose into cells and accelerates the conversion of glucose into glycogen in the liver, thereby decreasing the blood glucose level.
• A person fasts for 12 hours: Blood glucose level decreases. Glucagon production increases, which accelerates the conversion of glycogen (in the liver) and amino acids (in tissues) into glucose, thereby increasing the blood glucose level.

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Chapter 5: Immunity and Healthcare

Question 1: From the sequence of activities related to phagocytosis, select the correct answer.
(a) Expulsion of waste materials
(b) Engulfment of pathogens in phagosome
(c) Enzymes destroy the pathogen
(d) Phagocyte approaches the pathogen
(e) Phagolysosome is formed
Answer: ii) d, b, e, c, a.

• (d) Phagocyte approaches the pathogen.
• (b) Engulfment of pathogens in phagosome.
• (e) Phagolysosome is formed.
• (c) Enzymes destroy the pathogen.
• (a) Expulsion of waste materials.

Question 3: Which of the following is the correct pair of phagocytes?

• Eosinophil, Neutrophil
• Neutrophil, Monocyte
• Basophil, Neutrophil
• Monocyte, Lymphocyte
  Answer: Neutrophil, Monocyte.
• Neutrophils and monocytes are the white blood cells that participate in phagocytosis (the process of engulfing and destroying pathogens).

Question 4: Analyse the given table and find the one in which both the statement and the reason are correct.

Sl No.	Statement	Reason
(ii)	Blood clotting is a defence mechanism.	Prevents the flow of blood as well as blocks the entry of pathogens when there is a wound.
Answer: (ii).

• Blood clotting is a mechanism that prevents blood flow and blocks the entry of pathogens into the body when a wound forms on the skin, thus functioning as an immune mechanism.

Question 5: From the following, select the statements that are correct, regarding vaccines:

• Vaccines act as antigens.
• The immunity produced by vaccines is innate immunity.
• Vaccines help to produce antibodies against pathogens.
• All vaccines contain deactivated pathogens.
  Answer: The correct statements are:

1. Vaccines act as antigens.
2. Vaccines help to produce antibodies against pathogens.

Question 7: Analyse the table showing certain pathogens in an area and the number of people affected by them and answer the questions. (Pathogens: Naegleria fowleri 23, Leptospira 12, Plasmodium 57, Filarial worm 35)
i) Which disease affected more people in the region?
Answer: Plasmodium (Malaria), with 57 infected people.
ii) Which bacterial disease affected the people?
Answer: Leptospira (Rat fever/Leptospirosis), with 12 infected people.
iii) Which pathogen affected the residents who bathed in stagnant fresh water?
Answer: Naegleria fowleri (causes amoebic encephalitis), which is mainly found in stagnant and warm fresh water.

Question 8: Give reasons. Although antibiotics are effective medicines, their irrational use is harmful.
Answer: Unscientific and excessive use of antibiotics is harmful because it leads to several negative consequences:

1. Antibiotic Resistance: This is a major concern where bacteria develop resistance against the drugs, making treatment complicated.
2. Side Effects: Causes problems in the digestive system (diarrhoea, vomiting).
3. Organ Damage: Can lead to damage to the liver and kidneys.
4. Destruction of Beneficial Bacteria: Results in the destruction of beneficial bacteria that reside in the intestine.

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Chapter 6: Biology and Technology

Question 1: Which of the following statements about recombinant DNA technology is correct?
I. Restriction enzymes are used to cut the DNA of an organism.
II. Ligase enzymes join the cut DNA fragments together.
III. Vectors are usually bacterial plasmids.
IV. When recombinant DNA enters a host cell, it does not replicate.
Answer: b) I, II, III only.

• I. Restriction Endonuclease Enzyme is known as genetic scissors that cuts a specific gene.
• II. Ligase enzyme (genetic glue) joins two DNA segments.
• III. Plasmids (circular DNA in bacteria) are used as gene vectors.
• (IV is incorrect; the new recombinant DNA must become active in the host cell to replicate and form the desired product).

Question 2: Identify A, B, and C and choose the correct option.
A: A technology that joins together DNA segments from two or more different organisms
B: A technology used to locate genes in DNA
C: A technology used to identify individuals by analysing the arrangement of nucleotides in DNA
Answer: i) A - Recombinant DNA Technology, B - Gene Mapping, C - DNA Fingerprinting....

Question 3: What is the importance of the host cell in recombinant DNA technology? Analyse how this technology would be limited if there were no host cells.
Answer:

• Importance: The host cell is where the recombinant DNA (formed by ligating the desired gene into a vector, like a plasmid) is inserted. Once inserted, the genes become active, and the host cell multiplies, thereby producing the desired products (e.g., insulin).
• Limitation: If there were no host cells, the technology would be severely limited because the recombinant DNA could not be replicated, multiplied, or expressed to produce the desired products or traits in large quantities.

Question 4: Analyse how the information provided by the Human Genome Project will help in the future development of recombinant DNA technology, CRISPR editing technology and AI in biology.
Answer: The Human Genome Project (HGP) provided crucial foundational information, including the exact sequence of the 300 crore base pairs in the human genome and the location of genes. This detailed knowledge aids future technologies...:

• CRISPR Technology: HGP data allows researchers to precisely identify the specific DNA segment (target) that needs to be cut or edited.
• Recombinant DNA Technology: HGP knowledge aids in the precise identification of desirable genes necessary to cut, ligate, and insert into vectors.
• AI in Biology: AI relies on analyzing large amounts of genetic data (Bioinformatics). HGP data enables AI to predict disease causes, suggest new treatment methods, and design personalized medicine based on an individual’s genetic makeup....

Question 6: Analyse the fundamental similarities and differences between recombinant DNA technology and gene therapy.
Answer:

• Similarities: Both technologies fundamentally involve altering the genetic makeup of an organism. Both aim to introduce or utilize functional genes to achieve a desired outcome.
• Differences:
  • Recombinant DNA Technology typically focuses on combining DNA segments from two or more organisms, often utilizing host cells (like bacteria) for large-scale production of a product (e.g., insulin).
  • Gene Therapy is a specific medical application where defective genes in a patient are removed and replaced with functional genes to treat a disease.

Question 7: Observe the illustration and answer the questions. (Illustration shows Guide RNA (A) leading Cas9 enzyme (B) to target DNA).
a) Name the technology indicated in the illustration.
Answer: CRISPR technology.
c) What is the role of A and B?
Answer:

• A (Guide RNA or gRNA): It precisely identifies the DNA segment that needs to be cut (Identifying the target).
• B (Cas9 enzyme): It acts as the genetic scissors that cuts the DNA segment identified by the guide RNA.

Question 8 (Abridged): Explain how the perpetrator can be identified by analysing a DNA fingerprinting report in a forensic case. How can this technology be used to identify the unidentified dead bodies found in natural disasters?
Answer:

• Identifying the Perpetrator: DNA fingerprinting analyzes the unique sequence and pattern of nucleotides, particularly the repeated sequences in the "junk DNA" part, which vary significantly between individuals. In a forensic case, the DNA pattern obtained from the sample (hair, blood, or saliva) at the scene of the crime is compared with the DNA patterns of suspects. A match confirms the identity of the culprit.
• Identifying Dead Bodies: This technology is utilized to identify victims of accidents or disasters because an individual’s DNA pattern is unique, like a fingerprint. The unidentified body's DNA pattern can be compared to known DNA patterns of immediate family members (parents or offspring) to determine the biological relationship and thus establish the identity.

Question 9: How does artificial intelligence (AI) help data analysis and discoveries in biological research?
Answer: AI plays a major role in biological study by handling and interpreting complex data:

• Bioinformatics: AI analyzes large amounts of genetic data, assisting in sequencing and suggesting simplification strategies.
• Personalised Medicine: AI analyzes an individual's genetic makeup and health information to recommend the most suitable treatment regimens.
• Drug Discovery and Treatment: AI is used for discovering new drugs, predicting the effectiveness of chemical substances, and assisting in disease diagnosis and treatment recommendations.