Zoology in NEET is memory heavy but not memory only, because the diagram based and assertion reason questions need understanding. This set runs through human physiology, animal kingdom and classification, structural organisation, genetics and evolution, biotechnology, and ecology. Explanations point to the NCERT line the question came from, so revision stays anchored to the source text.
What is the significance of Agrobacterium tumefaciens in plant genetic engineering?
Answer: B
Agrobacterium tumefaciens naturally transfers its T-DNA into plant cells, making it an excellent natural vector for creating transgenic plants.
Q.262Medium
Which enzyme is used to synthesize cDNA from mRNA in reverse transcription?
Answer: A
Reverse transcriptase, derived from retroviruses, synthesizes complementary DNA (cDNA) from an mRNA template, essential for expressing eukaryotic genes in prokaryotes.
Q.263Medium
What is the main advantage of using embryonic stem cells (ESCs) in regenerative medicine?
Answer: B
Embryonic stem cells (ESCs) are pluripotent, meaning they can self-renew indefinitely and differentiate into any type of cell in the body, making them valuable for regenerative medicine.
Q.264Medium
In the context of gene therapy for hereditary diseases, what is the significance of using an inert viral vector that has had its pathogenic genes removed?
Answer: B
Modified viral vectors with pathogenic genes removed can efficiently deliver therapeutic genes to target cells while being non-pathogenic and reducing immune rejection.
Q.265Medium
In monoclonal antibody production using hybridoma technology, what is the advantage of fusing B cells with myeloma cells?
Answer: A
Hybridomas combine the antibody-producing capability of B cells with the immortality of myeloma cancer cells, producing monoclonal antibodies of high specificity indefinitely.
Q.266Medium
Which of the following applications of biotechnology can help in detecting antibiotic-resistant bacteria in clinical samples?
Answer: A
DNA microarrays can detect antibiotic resistance genes rapidly by analyzing the genetic profile of bacteria, enabling faster identification compared to traditional culture methods.
Q.267Medium
What is the principle behind the polymerase chain reaction (PCR) that allows exponential amplification of specific DNA sequences?
Answer: A
PCR works through repeated cycles of three temperatures: denaturation (95°C), annealing (50-65°C), and extension (72°C), with Taq polymerase extending primers exponentially.
Q.268Medium
What is the primary concern with the application of synthetic biology in creating new organisms?
Answer: B
Synthetic biology raises significant biosafety and biosecurity concerns regarding uncontrolled release of synthetic organisms, potential ecological disruption, and dual-use implications.
Q.269Medium
Which modern sequencing technology allows for real-time monitoring of DNA synthesis, reducing sequencing time and cost?
Answer: C
Nanopore sequencing allows real-time DNA reading as strands pass through nanopores, enabling rapid and cost-effective long-read sequencing without amplification.
Q.270Medium
What is the significance of the Human Genome Project in biotechnology and personalized medicine?
Answer: A
The Human Genome Project provided the complete human genetic blueprint, revolutionizing our understanding of genetic diseases and enabling personalized medicine approaches.
Q.271Medium
In vaccine development using biotechnology, what is the advantage of mRNA vaccines (like those for COVID-19) over traditional inactivated vaccines?
Answer: B
mRNA vaccines can be designed and produced rapidly, manufactured at scale, and trigger robust immune responses without requiring actual pathogenic agents.
Q.272Medium
What is the primary application of AFLP (Amplified Fragment Length Polymorphism) in forensic biotechnology?
Answer: B
AFLP generates unique DNA fingerprints by analyzing polymorphic bands through selective amplification and is widely used in forensic identification and paternity testing.
Q.273Medium
Which of the following is the causative agent of Amoebiasis (Amoebic dysentery) in humans?
Answer: B
Understanding:
We need to identify the correct pathogen responsible for causing amoebiasis (amoebic dysentery) in humans.
Step 1: Identify each organism
Plasmodium vivax causes malaria, transmitted by female Anopheles mosquito.
Entamoeba histolytica is a protozoan parasite that lives in the large intestine and causes amoebiasis.
Giardia lamblia causes giardiasis, characterised by diarrhoea and malabsorption.
Step 2: Pathogenesis of Entamoeba histolytica
Entamoeba histolytica colonises the large intestine, produces flask-shaped ulcers in the intestinal mucosa, and causes symptoms like abdominal pain, cramps, and bloody mucous stools. It spreads via contaminated food and water (faeco-oral route).
Answer:
The causative agent of amoebiasis is Entamoeba histolytica.
Quick Tip:
Remember that the housefly (Musca domestica) acts as a mechanical carrier transmitting Entamoeba histolytica cysts from faeces to food — a common exam fact.
Q.274Medium
In the immune response, which type of immunity is provided by the secretion of antibodies by B lymphocytes against a pathogen?
Answer: C
Understanding:
We need to identify the type of immunity that involves antibody secretion by B lymphocytes.
Step 1: Classify types of adaptive immunity
Adaptive immunity has two major arms:
•Humoral immunity: mediated by B lymphocytes that differentiate into plasma cells and secrete antibodies (immunoglobulins) into blood and lymph.
•Cell-mediated immunity: mediated by T lymphocytes (cytotoxic T cells) that directly kill infected or abnormal cells without antibody involvement.
Step 2: Eliminate incorrect options
Innate non-specific immunity includes barriers like skin, mucus, and phagocytes — it does not involve B cells or antibodies.
Passive acquired immunity refers to receiving ready-made antibodies (e.g., from mother through placenta or colostrum), not the process of B cells secreting antibodies in response to a pathogen.
Step 3: Confirm correct answer
The secretion of antibodies by B lymphocytes in response to antigens constitutes humoral immunity, because antibodies circulate in body fluids (humor = fluid).
Answer:
The type of immunity involving antibody secretion by B lymphocytes is humoral immunity.
Quick Tip:
Humoral = antibody-mediated (B cells); Cell-mediated = T cell-mediated. This distinction is frequently tested in NEET.
Q.275Medium
Which of the following cancers is correctly matched with the type of tumour it represents?
Answer: C
Understanding:
We need to correctly match a cancer type with the tissue of origin and whether it is benign or malignant.
Step 1: Analyse each option
Melanoma — It is a malignant tumour of melanocytes, not benign. This makes option A incorrect.
Leukaemia — It is a cancer of blood-forming cells (bone marrow), not exclusively lymph nodes. Option B is incorrect.
Carcinoma — It is indeed a malignant tumour that arises from epithelial cells (skin, lining of organs). This is the standard classification used in oncology and NCERT.
Sarcoma — It arises from connective/muscular tissues (bone, cartilage, muscle), not blood-forming cells. Option D is incorrect.
Step 2: Confirm classification of carcinomas
Carcinomas form the largest group of cancers in humans. Examples include lung carcinoma, breast carcinoma, and colon carcinoma, all originating from epithelial cells.
Answer:
Carcinoma is correctly defined as a malignant tumour arising from epithelial cells.
Quick Tip:
Remember the classification: Carcinoma (epithelial) → Sarcoma (connective/muscle) → Leukaemia/Lymphoma (blood/lymphoid). Melanoma is always malignant — never benign.
Q.276Medium
In malaria caused by Plasmodium falciparum, the fever occurs every 48 hours. This periodicity is linked to which event in the parasite's life cycle?
Answer: B
Understanding:
We need to identify the specific event in the Plasmodium life cycle responsible for the periodic fever seen in malaria.
Step 1: Trace the erythrocytic cycle
After entering the liver (pre-erythrocytic stage), merozoites are released and invade red blood cells (RBCs). Inside RBCs, they feed on haemoglobin and multiply. At the end of each erythrocytic cycle, the RBCs rupture, releasing new merozoites along with toxic metabolic byproducts including haemozoin (malarial pigment) and other pyrogens.
Step 2: Link rupture to fever
The sudden release of merozoites, haemozoin, and cellular debris into the bloodstream triggers the immune system, causing a sharp rise in body temperature. In Plasmodium falciparum (malignant tertian malaria) and P. vivax (benign tertian malaria), the erythrocytic cycle is completed every 48 hours, giving a fever every 2nd day.
Step 3: Eliminate incorrect options
Sporozoite release from the mosquito initiates infection but does not cause fever.
Gametocytes form in RBCs (not liver cells) and are the sexual stage for the mosquito — not linked to fever periodicity.
Zygote formation occurs inside the mosquito's gut — irrelevant to fever in humans.
Answer:
The periodic fever in malaria is caused by the rupture of infected red blood cells, releasing merozoites and haemozoin into the bloodstream.
Quick Tip:
P. vivax and P. falciparum → 48-hour cycle (tertian fever); P. malariae → 72-hour cycle (quartan fever). This is a high-frequency NEET fact.
Q.277Medium
Widal test is used for the diagnosis of which of the following diseases?
Answer: A
Understanding:
We need to identify which disease is diagnosed using the Widal test.
Step 1: Identify the Widal test
The Widal test is a serological agglutination test that detects antibodies (agglutinins) in the patient's serum against Salmonella typhi antigens — specifically the O (somatic) and H (flagellar) antigens. A significant rise in titre confirms typhoid fever.
Step 2: Eliminate other options
Malaria is diagnosed by peripheral blood smear microscopy, rapid antigen (RDT) tests, or PCR.
Cholera is diagnosed by stool culture and dark-field microscopy for Vibrio cholerae.
Amoebiasis is diagnosed by stool examination for Entamoeba histolytica cysts or trophozoites.
Step 3: Confirm
The Widal test is exclusively used for diagnosing typhoid (enteric fever) caused by Salmonella typhi.
Answer:
The Widal test is used for the diagnosis of typhoid fever.
Quick Tip:
The Widal test is named after French physician Georges-Fernand Widal. An agglutination titre of 1:160 or above for O antigen is considered significant in most clinical settings — worth remembering for applied MCQs.
Q.278Medium
Which of the following drugs acts by binding to opioid receptors in the central nervous system, producing analgesia and euphoria, and is derived from the latex of Papaver somniferum?
Answer: B
Understanding:
We need to identify the drug that binds to opioid receptors, produces analgesia and euphoria, and is derived from Papaver somniferum (opium poppy).
Step 1: Identify the source plant and mechanism for each option
Cocaine — derived from Erythroxylum coca; it inhibits reuptake of dopamine, serotonin, and norepinephrine; classified as a stimulant, not an opioid.
Morphine — derived from the latex of Papaver somniferum; it directly binds to opioid receptors (mu, kappa, delta) in the CNS, producing powerful analgesia and euphoria; classified as an opioid narcotic analgesic.
Cannabis — derived from Cannabis sativa; acts on cannabinoid receptors (CB1, CB2), not opioid receptors.
LSD (Lysergic acid diethylamide) — a synthetic hallucinogen derived from ergot fungus; acts primarily on serotonin receptors.
Step 2: Confirm
Morphine satisfies all three criteria: opioid receptor binding, analgesia and euphoria, and derivation from Papaver somniferum latex.
Answer:
Morphine is the drug derived from Papaver somniferum latex that binds to opioid receptors to produce analgesia and euphoria.
Quick Tip:
All three — morphine, heroin (diacetylmorphine), and codeine — are opioids from Papaver somniferum. Heroin is synthesised by acetylation of morphine and is more potent due to faster CNS penetration.
Q.279Medium
In the context of AIDS, the virus HIV preferentially infects which type of cells, leading to progressive immunodeficiency?
Answer: C
Understanding:
We need to identify the primary target cell of HIV that leads to progressive collapse of the immune system in AIDS.
Step 1: Mechanism of HIV infection
HIV (Human Immunodeficiency Virus) is a retrovirus. Its surface glycoprotein gp120 binds specifically to the CD4 receptor present on the surface of helper T lymphocytes (T-helper cells / CD4+ T cells). The co-receptors CCR5 or CXCR4 also facilitate entry.
Step 2: Consequence of CD4+ T cell depletion
Helper T cells are the master regulators of adaptive immunity. They stimulate B cells to produce antibodies (humoral arm) and activate cytotoxic T cells (cell-mediated arm). Progressive destruction of CD4+ T cells by HIV reduces their count from the normal range of 500–1500 cells/µL. When the count falls below 200 cells/µL, the patient is diagnosed with AIDS and becomes susceptible to opportunistic infections.
Step 3: Eliminate incorrect options
CD8+ T cells (cytotoxic) and NK cells are not the primary targets of HIV.
B lymphocytes lack CD4 receptors and are not directly infected.
Answer:
HIV preferentially infects helper T cells (CD4+ T cells), destroying them and leading to progressive immunodeficiency (AIDS).
Quick Tip:
The CD4+ T cell count is the key diagnostic and prognostic marker in HIV/AIDS. A count below 200 cells/µL defines AIDS irrespective of symptoms.
Q.280Medium
Which of the following statements correctly describes the role of memory cells in secondary immune response?
Answer: B
Understanding:
We need to identify the correct description of the role of memory cells in the secondary immune response.
Step 1: Formation of memory cells
During the primary immune response (first exposure to an antigen), some activated B and T lymphocytes differentiate into long-lived memory cells instead of effector cells. These memory cells persist in the body for years or even a lifetime.
Step 2: Role in secondary immune response
On second exposure to the same antigen, memory cells are rapidly activated and proliferate quickly (clonal expansion). This results in:
•A faster immune response (lag period is much shorter)
This is called an anamnestic (secondary) response and forms the immunological basis of vaccination.
Step 3: Eliminate incorrect options
Memory cells are produced during the primary immune response, not only the secondary one.
Memory B cells lead to antibody production; they do not directly kill cells (that is the role of cytotoxic T cells).
Memory cells are long-lived — they can persist for decades, not just a few days.
Answer:
Memory cells respond rapidly to a second antigenic exposure, producing a faster and stronger antibody response than the primary immune response.
Quick Tip:
The secondary immune response is the scientific basis of booster doses in vaccination — the booster rapidly reactivates memory cells to produce high antibody titres.
