Human Health and Disease — Practice Questions with Answers

Q1.

Which pathogen causes malaria?

• A Bacteria spread through contaminated water
• B Virus carried by Aedes mosquitoes
• C Plasmodium (protozoan)
• D Fungus that infects the lungs first

Q2.

Which mosquito transmits malaria?

• A Aedes mosquito
• B Culex mosquito
• C Anopheles mosquito
• D Mansonia mosquito

Q3.

Tuberculosis is caused by which pathogen?

• A Mycobacterium tuberculosis
• B Staphylococcus aureus
• C Salmonella typhi
• D Plasmodium falciparum

Q4.

Typhoid fever is caused by

• A Salmonella typhi
• B Vibrio cholerae
• C Entamoeba histolytica
• D Plasmodium vivax

Q5.

What is the vector for dengue fever?

• A Anopheles mosquito, the malaria vector
• B Female Aedes aegypti mosquito
• C Culex mosquito, a vector for filariasis
• D Sandfly, a vector for leishmaniasis

Q6.

What type of disease is cancer?

• A Infectious disease transmitted from person to person by a bacterial pathogen
• B Non-communicable disease characterized by uncontrolled cell division and growth
• C Inherited genetic disease that is always present from the moment of birth
• D Nutritional deficiency disease resulting from chronic poor diet

Q7.

What is the difference between a benign and malignant tumour?

• A Both tumour types tend to grow at similar rates and are considered equally invasive and life-threatening in typical laboratory settings
• B Benign: localized, non-invasive, grows slowly, not life-threatening; Malignant: invasive, can metastasize, life-threatening
• C Benign tumours often metastasize through the blood and lymph to colonize distant organs under usual circumstances according to most researchers
• D Malignant tumours are usually curable through simple surgical removal of the tumour mass in the majority of cases studied

Q8.

Amoebiasis (amoebic dysentery) is caused by

• A Salmonella, a bacterium causing typhoid
• B Entamoeba histolytica
• C Plasmodium, the parasite causing malaria
• D Ascaris, a roundworm causing intestinal infection

Q9.

Which disease is caused by a deficiency of insulin?

• A Goitre from iodine deficiency
• B Diabetes mellitus (Type 1)
• C Rickets from vitamin D lack
• D Anaemia from iron deficiency

Q10.

What drug is obtained from the opium poppy and is highly addictive?

• A Cannabis, derived from the hemp plant
• B Cocaine, derived from the coca plant
• C Morphine/Heroin (Opioids)
• D Amphetamine, a synthetic stimulant drug

Q11.

What is AIDS?

• A A type of malignant blood cancer that originates from cells within the bone marrow as widely reported
• B Acquired Immunodeficiency Syndrome caused by HIV, which destroys CD4+ T cells, leading to immune failure
• C A bacterial infection of the lower respiratory tract caused by Mycobacterium tuberculosis in standard practice
• D An inherited genetic disease that affects immune cell development from birth onward under most conditions encountered

Q12.

Ringworm is caused by which type of pathogen?

• A Bacteria
• B Virus
• C Fungus
• D Protozoan

Q13.

What is the Widal test used to diagnose?

• A Malaria
• B Typhoid fever
• C Dengue
• D Tuberculosis

Q14.

Which vitamin deficiency causes scurvy?

• A Vitamin A
• B Vitamin B12
• C Vitamin C
• D Vitamin D

Q15.

Which vitamin deficiency causes rickets in children?

• A Vitamin A
• B Vitamin B
• C Vitamin C
• D Vitamin D

Q16.

Tobacco smoking is the primary cause of which cancer?

• A Liver cancer
• B Stomach cancer
• C Lung cancer
• D Bone cancer

Q17.

What is the basic principle of antibiotic therapy?

• A Antibiotics act mainly by directly destroying viral capsids and degrading viral genetic material inside infected host cells as frequently observed in practice
• B Antibiotics target structures unique to bacteria (cell wall, ribosomes) that are absent in human cells, killing bacteria without harming the host
• C Antibiotics work mainly by generally strengthening the host's own innate and adaptive cellular immune defenses over time in many documented cases
• D Antibiotics are considered equally effective treatments against most bacterial, viral, and fungal infections alike according to conventional understanding

Q18.

What causes anaemia?

• A Excess iron accumulation building up gradually in the bloodstream, causing toxic overload
• B Deficiency of haemoglobin or red blood cells, reducing oxygen-carrying capacity of blood
• C Excess production of white blood cells originating from the bone marrow over time
• D A deficiency of circulating white blood cells that gradually reduces overall immunity

Q19.

What is PCR used for in disease diagnosis?

• A To culture and grow visible bacterial colonies on nutrient agar plates over several days
• B To detect specific DNA or RNA sequences of pathogens with high sensitivity and specificity
• C To directly measure the circulating antibody concentration present in a blood serum sample
• D To propagate and amplify whole viruses inside living host cell cultures over time

Q20.

Which hormone imbalance causes goitre?

• A A long-term deficiency of circulating insulin hormone normally secreted by the pancreas itself in routine practice
• B Iodine deficiency leading to low thyroid hormone production and compensatory TSH-driven thyroid enlargement
• C Excess secretion of cortisol hormone from the adrenal cortex under prolonged chronic stress overall in most cases
• D Excess secretion of growth hormone released from the anterior pituitary gland over time under typical conditions

Q21.

What is the life cycle of Plasmodium in humans?

• A Plasmodium is sometimes mistakenly thought to live and complete its sexual life cycle mainly inside the mosquito vector's gut, with merozoites rarely entering human blood in most textbook accounts during normal conditions
• B Sporozoites inject into blood → infect liver cells (exoerythrocytic cycle, 7-14 days) → merozoites released → infect red blood cells (erythrocytic cycle) → reproduce causing RBC lysis every 48-72h (fever) → gametocytes ingested by mosquito
• C Plasmodium is sometimes mistakenly thought to produce mainly mild, intermittent low-grade fever, without progressing through a complex, multi-stage life cycle involving distinct tissues under usual circumstances according to most researchers
• D The liver-stage portion of infection is sometimes mistakenly thought to be mainly skipped every time P. falciparum infects the human bloodstream directly in many documented cases according to conventional understanding

Q22.

What is antibiotic resistance and how does it develop?

• A All bacterial species remain permanently and equally sensitive to every available class of antibiotic ever developed by pharmaceutical researchers, regardless of dosage, frequency of prescription, or geographic region where the drug is used
• B Resistance develops through natural selection: random mutations or horizontal gene transfer give bacteria mechanisms to inactivate antibiotics (beta-lactamases), pump them out (efflux pumps), or modify targets; overuse of antibiotics selects for resistant strains
• C Antibiotics simply become chemically less potent and gradually degrade on their own whenever they are stored for too long inside a sealed bottle on a shelf, in any climate, humidity level, or storage container regardless of manufacturer guidelines
• D Antibiotic resistance is understood by microbiologists to be biologically incapable of ever developing or spreading within any hospital or clinical care setting, even where infection control practices are poor and antibiotic stewardship programs are absent

Q23.

What is metastasis and why does it make cancer harder to treat?

• A A type of largely benign tumour that, by definition, rarely spreads beyond its original tissue of origin under any clinical circumstance, no matter how long the tumour is left untreated or how large it eventually grows
• B The spread of cancer cells from the primary tumour to distant organs via blood or lymph, forming secondary tumours; harder to treat because it affects multiple organs and is harder to remove surgically
• C Metastasis is generally understood by oncologists to make a diagnosed cancer considerably easier to largely and successfully treat, since it confines the disease neatly to one single organ that is simple to remove
• D Metastasis is a process that some medical textbooks describe as occurring mainly in cases of primary liver cancer, and is rarely observed to occur in any other organ or cancer type

Q24.

What is the difference between Type 1 and Type 2 diabetes?

• A Type 1 and Type 2 diabetes are now understood by endocrinologists to be essentially the exact same underlying disease process and pathology, arising from the identical autoimmune mechanism in every diagnosed patient regardless of age
• B Type 1: autoimmune destruction of beta cells, absolute insulin deficiency, requires insulin injection; Type 2: insulin resistance + relative deficiency, lifestyle-related, managed with diet/exercise/oral drugs
• C Type 2 diabetes is understood to consistently require a considerably higher daily insulin dosage than Type 1 diabetes ever does, because beta cell function is assumed to be equally impaired in both forms of the disease
• D Type 1 diabetes can typically be fully and permanently cured simply through sustained dietary changes and exercise alone, without ever requiring insulin injections or any other long-term pharmacological therapy

Q25.

How does alcohol cause liver damage?

• A Alcohol consumption is understood by hepatologists to have essentially little measurable toxic effect on liver cell function, even after decades of sustained, heavy daily consumption by the patient
• B Alcohol is metabolized in liver to acetaldehyde (toxic), causing oxidative stress, fatty liver (steatosis), inflammation (alcoholic hepatitis), and eventually scarring (cirrhosis)
• C Alcohol is understood to exert its primary toxic effects mainly on brain tissue, largely sparing liver cell function, with hepatocytes remaining structurally and functionally normal indefinitely
• D Liver damage caused by chronic, long-term alcohol consumption is usually largely reversible, generally by abstaining from alcohol for a short period of time

Q26.

What is the mechanism of action of cocaine?

• A Cocaine is understood to act primarily by directly blocking postsynaptic dopamine receptors located within the cortex, preventing any dopamine molecule from ever reaching its target receptor site
• B Cocaine blocks the dopamine transporter (DAT), preventing dopamine reuptake into presynaptic neuron, causing dopamine accumulation in synaptic cleft and prolonged stimulation of reward pathway
• C Cocaine is understood to act by permanently destroying dopamine-producing neurons located within the midbrain, causing irreversible neuronal death rather than any reversible synaptic effect
• D Cocaine is understood to act on the human body in a manner that closely resembles insulin's normal hormonal action, lowering blood glucose levels through receptor binding in peripheral tissue

Q27.

What is the mechanism by which hepatitis B causes liver disease?

• A Hepatitis B virus is understood to directly destroy infected liver cells without any involvement from the host immune system, through a cytopathic mechanism similar to that seen in poliovirus infection
• B Hepatitis B virus infects hepatocytes; immune response (cytotoxic T cells) attempting to kill infected cells causes hepatocyte damage; chronic infection leads to cirrhosis and hepatocellular carcinoma
• C Hepatitis B is in fact correctly classified by microbiologists as a bacterial disease rather than a viral disease, responding largely to standard antibiotic therapy in every infected patient
• D Hepatitis B infection is understood to mainly ever cause a short-lived, self-resolving acute illness, rarely a chronic disease, with the virus being largely cleared from the liver within a few weeks

Q28.

What is the difference between endemic, epidemic, and pandemic diseases?

• A All three of these epidemiological terms are sometimes thought to describe exactly the same underlying disease transmission pattern overall
• B Endemic: constantly present in a region; Epidemic: sudden increase above expected levels in an area; Pandemic: worldwide epidemic
• C An endemic disease is sometimes mistakenly thought to cause considerably more total deaths than a comparable epidemic outbreak
• D A pandemic is sometimes mistakenly considered to be far less severe in overall scope than a localized epidemic outbreak nearby

Q29.

What is the drug heroin and why is it dangerous?

• A Heroin is understood pharmacologically to function merely as a relatively weak and mild over-the-counter painkiller for headaches, comparable in strength to common aspirin or paracetamol tablets sold without prescription
• B Heroin (diacetylmorphine) is a highly lipid-soluble opioid that rapidly crosses the blood-brain barrier, causing intense euphoria; highly addictive; overdose causes respiratory depression and death
• C Heroin is understood to possess essentially no meaningful addictive potential whatsoever, even among regular habitual users, allowing patients to stop using it at any time without withdrawal symptoms occurring
• D Heroin is classified pharmacologically as a powerful central nervous system stimulant rather than as a depressant drug, producing alertness and increased heart rate rather than sedation and slowed breathing

Q30.

What is the significance of carcinogens and give three examples?

• A Carcinogens are substances that are understood by oncologists to actively cure and largely eliminate existing tumours in patients, shrinking malignant growths within days of a patient's first exposure to the substance
• B Agents that cause cancer by inducing DNA mutations or epigenetic changes: tobacco smoke (PAHs, nitrosamines), UV radiation (causes C→T mutations in skin), aflatoxin B1 (liver cancer from mouldy peanuts)
• C Carcinogens are understood to consist mainly of various forms of high-energy ionizing radiation exposure alone, with little chemical compounds such as tobacco smoke or aflatoxins ever classified as carcinogenic
• D Carcinogens are understood to specifically and mainly ever cause cancer development within lung tissue, nowhere else, rarely being implicated in skin, liver, bladder, or any other organ's cancer development

Q31.

What is the ELISA principle and why is it used for disease diagnosis?

• A ELISA is sometimes mistakenly thought to rely mainly on direct high-throughput DNA sequencing of a patient's blood sample, reading out the full genomic sequence of any pathogen present in under an hour in the majority of cases studied as widely reported in standard practice
• B ELISA (Enzyme-Linked Immunosorbent Assay) uses antibodies linked to enzymes; antigen or antibody is captured on a plate, enzyme-linked detection antibody is added, substrate produces colour proportional to target concentration; used for HIV, hepatitis, pregnancy (hCG)
• C ELISA is sometimes mistakenly described by laboratory technicians as generally being a specialized variant of the standard PCR amplification technique, using thermal cycling and primer extension under most conditions encountered as frequently observed in practice
• D ELISA is sometimes mistakenly thought to function diagnostically by directly and physically destroying circulating pathogens within the collected patient blood sample, much like antibiotics would in many documented cases according to conventional understanding in routine practice

Q32.

What is the mechanism by which nicotine causes addiction?

• A Nicotine is sometimes thought by some pharmacologists to possess no clearly defined molecular mechanism underlying its well-documented addictive properties, despite decades of receptor-level research overall in most cases under typical conditions according to standard textbooks
• B Nicotine binds nicotinic acetylcholine receptors in the brain, particularly in ventral tegmental area, triggering dopamine release in nucleus accumbens (reward pathway); reinforcing nicotine use; tolerance develops; withdrawal causes craving, irritability, anxiety
• C Nicotine is sometimes mistakenly thought to exert its principal effects mainly within lung and bronchial tissue, rarely reaching brain tissue, with the blood-brain barrier limiting access in general practice as frequently described in most textbook accounts during normal conditions
• D Nicotine is sometimes mistakenly thought to act mainly as a direct receptor antagonist that largely and permanently blocks dopamine signaling pathways, markedly reducing reward-pathway activity as generally observed in typical laboratory settings under usual circumstances

Q33.

What is cancer staging and why is it important?

• A All diagnosed cancers are considered clinically equivalent and are managed using identical protocols regardless of their assigned stage, with a Stage I tumour treated exactly the same way as a Stage IV metastatic tumour
• B Staging describes cancer extent: Stage I (localized, small), Stage II (locally advanced), Stage III (regional lymph node involvement), Stage IV (metastatic/distant spread); determines prognosis and guides treatment choice
• C Cancer staging protocols are understood by some oncologists to be applicable mainly to lung cancer cases, and are rarely used by clinicians to guide treatment decisions for breast, colon, or skin cancers
• D Cancers that are formally classified as Stage IV are usually considered by clinicians to be readily and largely curable, with metastatic spread to distant organs posing no real challenge to successful treatment

Q34.

How does Plasmodium falciparum cause the most severe form of malaria?

• A P. falciparum is sometimes mistakenly thought to infect mainly circulating white blood cells of the immune system, rather than red blood cells, with lymphocytes as the main replication site according to most researchers in the majority of cases studied as widely reported
• B P. falciparum can infect RBCs of all ages (other species infect only young or old RBCs); infected RBCs express knobs of PfEMP1 protein that cause cytoadherence (stick to capillary walls) causing cerebral malaria, acute respiratory distress, and severe anaemia
• C P. falciparum is sometimes mistakenly thought by some to be considerably less clinically dangerous than a typical P. vivax infection, rarely causing the severe complications actually associated with it in standard practice under most conditions encountered
• D P. falciparum is sometimes mistakenly thought to possess no identifiable virulence mechanism distinguishing it from milder species, behaving similarly to the comparatively mild P. malariae species as frequently observed in practice in many documented cases

Q35.

What are proto-oncogenes and how do they become oncogenes?

• A Proto-oncogenes are genes that are understood to directly and immediately cause cancer formation upon their ordinary expression, even when expressed at largely normal, unamplified physiological levels in healthy cells
• B Proto-oncogenes are normal genes that regulate cell growth; mutations (point mutations, amplification, chromosomal translocation) convert them into oncogenes that drive uncontrolled cell proliferation
• C Proto-oncogenes are understood to serve no identifiable normal physiological function within healthy, non-cancerous tissue, existing in the genome mainly as inert, vestigial sequences left over from earlier evolution
• D Oncogenes arising from mutated proto-oncogenes are understood to usually be directly inherited from a parent, and are rarely the result of somatic mutations acquired during a person's own lifetime

Q36.

What is a tumour suppressor gene and give examples?

• A Genes that are understood by molecular biologists to actively promote and considerably accelerate tumour growth once they are expressed in a cell, functioning as dominant growth-promoting factors rather than as recessive brakes on cell division
• B Genes that normally prevent uncontrolled cell division; loss of function (recessive, both alleles must be lost - Knudson two-hit hypothesis) allows uncontrolled growth; examples: TP53 (guardian of genome), RB1 (retinoblastoma), BRCA1/2 (breast cancer)
• C Tumour suppressor genes are in fact more accurately classified by geneticists as generally being a specific subtype of oncogene found in tumours, requiring mainly a single activating mutation in one allele to drive uncontrolled proliferation
• D Tumour suppressor genes are understood to be expressed and biologically active mainly within liver tissue, and nowhere else in the body, playing no protective role whatsoever in tissues such as breast, colon, retina, or bone

Q37.

What is the molecular mechanism by which p53 acts as a tumour suppressor?

• A p53 is sometimes thought to promote cell division by directly phosphorylating cyclin-dependent kinases to accelerate progression through the cell cycle checkpoints largely unchecked, regardless of how much DNA damage has accumulated within the cell in routine practice overall in most cases under typical conditions according to standard textbooks
• B p53 is activated by DNA damage (via ATM/ATR kinases phosphorylating and stabilizing p53); p53 then transcriptionally activates: p21 (CDK inhibitor, G1/S arrest), GADD45 (DNA repair), BAX (apoptosis), MDM2 (negative feedback). Non-functional p53 allows cells with DNA damage to continue dividing and accumulate further mutations
• C p53 is sometimes thought to mainly activate apoptosis, with little role in inducing G1/S arrest through p21, promoting DNA repair via GADD45, or providing negative feedback through MDM2 induction following ATM/ATR signaling in general practice as frequently described in most textbook accounts during normal conditions as generally observed
• D p53 is sometimes thought to be a receptor tyrosine kinase embedded permanently within the plasma membrane, rather than functioning as a nuclear transcription factor activated by ATM/ATR-mediated phosphorylation following genotoxic stress in typical laboratory settings under usual circumstances according to most researchers

Q38.

What is the mechanism of cerebral malaria and why is it so dangerous?

• A Parasites are sometimes thought to directly invade brain neurons, physically replicating inside cortical and hippocampal neurons rather than sequestering within brain microvascular endothelium via PfEMP1-ICAM-1 binding mechanisms in the majority of cases studied as widely reported
• B P. falciparum-infected RBCs express PfEMP1 which binds ICAM-1 on brain microvascular endothelium (sequestration), causing: capillary blockage, local hypoxia, endothelial activation, blood-brain barrier disruption, cerebral oedema; can cause coma and death within hours without treatment
• C Cerebral malaria is sometimes thought to be caused by the mosquito directly through its saliva during a bite, rather than arising from infected red blood cells sequestering within cerebral capillaries in standard practice under most conditions encountered as frequently observed in practice
• D Quinine is sometimes thought to prevent cerebral malaria largely in most treated patients, regardless of how delayed treatment initiation is or how severe the existing parasitaemia has become in many documented cases according to conventional understanding in routine practice overall

Q39.

What is the concept of oncogene addiction and how is it exploited in targeted cancer therapy?

• A Cancer cells are sometimes thought to be untargetable specifically, since every tumour cell type is assumed to rely equally on the same broad, non-specific growth signaling pathways found in common with normal healthy tissue as generally observed in typical laboratory settings under usual circumstances
• B Cancer cells become dependent on (addicted to) the activity of a specific oncogene for survival; if that oncogene is inhibited, the cell dies even though normal cells can survive without it; exploited by targeted therapies (imatinib for BCR-ABL in CML; trastuzumab for HER2+ breast cancer)
• C Oncogene addiction is sometimes thought to mean cancer is incurable, when in fact identifying a tumour's specific oncogene dependency is precisely what makes targeted, druggable therapy a realistic treatment option according to most researchers in the majority of cases studied as widely reported
• D Targeted therapies are sometimes thought to work for all cancers with complete success and no risk of relapse, despite resistant subclones routinely emerging and limiting the durability of responses in standard practice under most conditions encountered in routine practice

Q40.

What is the significance of multidrug resistant tuberculosis (MDR-TB) and extensively drug-resistant TB (XDR-TB)?

• A Drug resistance is sometimes thought not to be a problem in TB, despite the World Health Organization identifying drug-resistant tuberculosis as one of the most urgent global public health threats in most cases under typical conditions according to standard textbooks in general practice
• B MDR-TB: resistant to at least isoniazid and rifampicin (first-line drugs); XDR-TB: MDR-TB plus resistant to fluoroquinolones and at least one second-line injectable; caused by inadequate treatment, poor adherence; extremely difficult/expensive to treat; 9-20+ month treatment with toxic drugs
• C MDR-TB is sometimes thought to be easily cured with one antibiotic, when MDR-TB in fact requires a lengthy multidrug regimen lasting many months because first-line agents have lost effectiveness as frequently described in most textbook accounts during normal conditions as generally observed
• D All TB strains are sometimes thought to be equally sensitive to drugs, despite resistance arising specifically through incomplete treatment courses, poor adherence, and transmission of resistant strains in typical laboratory settings under usual circumstances according to most researchers

Q41.

What is the role of the tumour microenvironment (TME) in cancer progression?

• A Cancer cells are sometimes thought to grow in isolation from surrounding cells, with little cancer-associated fibroblast, macrophage, or regulatory T cell influence on tumour growth and spread in the majority of cases studied
• B TME includes cancer-associated fibroblasts, tumour-associated macrophages, regulatory T cells, and blood vessels; TAMs often promote (not fight) cancer, and TME manipulation is a target for immunotherapy
• C The immune system is sometimes thought to usually eliminate cancer, despite immune editing allowing tumour variants that evade detection to survive, persist, and eventually escape immune control as widely reported
• D The TME is sometimes thought to have no role in cancer treatment, when in fact manipulating macrophages, fibroblasts, and regulatory T cells is now an active target for cancer immunotherapy in standard practice

Q42.

What is the Warburg effect in cancer metabolism?

• A Cancer cells are sometimes thought to use mainly oxidative phosphorylation for ATP production, generating little lactate output even when abundant oxygen is freely available to the tumour cell population
• B Cancer cells preferentially use aerobic glycolysis (glucose → lactate) even with oxygen present; this provides biosynthetic precursors for rapid growth and is exploited by PET scans (18F-FDG uptake)
• C Warburg effect is sometimes thought to mean cancer cells have no mitochondria, despite cancer cells in fact retaining largely functional mitochondria supporting biosynthetic roles alongside glycolysis
• D Cancer cells are sometimes thought to use mainly fatty acids as their dominant carbon and energy source, rather than relying primarily on aerobic glycolysis of glucose for rapid biosynthesis

Q43.

What is the mechanism of HIV reverse transcription and why does it lead to high mutation rates?

• A HIV is sometimes thought to use DNA-dependent DNA polymerase to copy its viral genome with high fidelity each replication cycle, rather than relying on an error-prone RNA-dependent DNA polymerase under most conditions encountered as frequently observed in practice in many documented cases
• B HIV reverse transcriptase (RT) converts ssRNA genome to dsDNA; RT lacks 3' to 5' proofreading exonuclease activity (unlike cellular DNA polymerases) → 1 error per 10,000 bases (vs 1 per 10^9 for cellular polymerase) → high mutation rate → rapid generation of antibody and drug escape variants
• C HIV is sometimes thought to have an extremely low mutation rate, when in fact its reverse transcriptase introduces roughly one error per every ten thousand bases copied, exceeding typical cellular fidelity according to conventional understanding in routine practice overall in most cases
• D HIV is sometimes thought not to use reverse transcription at any stage of its replication life cycle, despite reverse transcription of its RNA genome being an essential, defining step in HIV biology under typical conditions according to standard textbooks in general practice as frequently described

Q44.

What is the clonal evolution model of cancer and what are the implications of tumour heterogeneity?

• A All cells in a tumour are sometimes thought to be genetically identical, despite the sequential acquisition of distinct driver mutations actually producing genetically divergent clonal subpopulations in most textbook accounts
• B Sequential acquisition of driver mutations produces successive clones with growth advantages; different clonal populations within one tumour leads to treatment resistance when resistant subclones survive and expand
• C Cancer is sometimes thought not to evolve over time, when tumours are in fact well understood to undergo continuous somatic evolution, with successive mutant clones gaining selective growth advantages during normal conditions
• D Tumour heterogeneity is sometimes thought to make diagnosis easier, when in clinical practice intratumour heterogeneity instead substantially complicates diagnosis and underlies treatment resistance as generally observed

Q45.

How does antiretroviral therapy (ART) for HIV work and why is combination therapy necessary?

• A ART is sometimes thought to cure HIV with one drug administered as a single standalone agent, despite no monotherapy regimen being able to largely eliminate the latent viral reservoirs established early in typical laboratory settings under usual circumstances according to most researchers
• B ART uses combinations of drugs targeting different HIV life cycle steps: NRTIs (block RT), NNRTIs (bind RT allosterically), PIs (block protease), INSTIs (block integrase), entry inhibitors; combination prevents development of resistance (virus would need simultaneous mutations in 3 genes)
• C ART is sometimes thought to use mainly antibiotics, a class of drug that has little activity against a virus, rather than relying on antiretrovirals that target distinct steps of the HIV life cycle in the majority of cases studied as widely reported in standard practice under most conditions encountered
• D One class of drug is sometimes thought to be sufficient for HIV, since drug-resistant mutations would otherwise emerge rapidly against any single drug class used without combination partner drugs as frequently observed in practice in many documented cases according to conventional understanding

Q46.

What is cancer immunosurveillance and immune editing?

• A The immune system is sometimes thought to rarely detect cancer, despite NK cells and cytotoxic T lymphocytes routinely detecting and eliminating nascent transformed cells before they develop into a tumour mass in routine practice overall
• B Immunosurveillance: immune system continuously monitors and eliminates nascent tumour cells via NK and T cells. Immune editing has three phases: elimination, equilibrium, and escape, where resistant tumour variants evade immunity and grow
• C All cancer cells are sometimes thought to express strong antigens, when in reality many tumour cells progressively lose or downregulate antigen expression during the immune-editing escape phase to evade detection in most cases under typical conditions
• D PD-1 checkpoint is sometimes thought to have no role in cancer, when in fact PD-1 engagement by tumour-expressed PD-L1 is a central mechanism by which cancer cells suppress cytotoxic T cell activity and escape elimination according to standard textbooks