NUMS — Medical & Dental Entry Test

NUMS Biology — Biodiversity: Viruses, Bacteria and Kingdoms (Set 3)

Take the NUMS Biology — Biodiversity: Viruses, Bacteria and Kingdoms (Set 3): 30 multiple-choice questions (40 minutes) with instant scoring and a full…

What this test covers

30 NUMS Biology

Sample questions with answers

The first 5 questions of this test, with the correct answer and explanation.

Q1. A virus has a protein coat made of repeating subunits arranged around its nucleic acid. These subunits are called:
- A. capsomeres ✓
- B. nucleosomes
- C. virions
- D. plasmids
Answer: A. capsomeres
Explanation: The capsid is made of protein subunits termed capsomeres.
Q2. Influenza viruses can change their surface antigens by reassortment of segments. This is possible because the influenza genome is:
- A. a single DNA molecule
- B. circular DNA
- C. double-stranded linear DNA
- D. segmented RNA ✓
Answer: D. segmented RNA
Explanation: The influenza genome consists of eight RNA segments, which can reassort when two strains infect the same cell.
Q3. An enzyme found in retroviruses but not in bacteriophages is:
- A. lysozyme
- B. RNA polymerase
- C. reverse transcriptase ✓
- D. DNA ligase
Answer: C. reverse transcriptase
Explanation: Retroviruses copy RNA into DNA with reverse transcriptase.
Q4. The HIV surface glycoprotein gp120 binds to which receptor on host cells?
- A. MHC class II only
- B. CD4 ✓
- C. CD8
- D. IgG
Answer: B. CD4
Explanation: gp120 binds CD4 on helper T cells, macrophages and dendritic cells.
Q5. A patient's CD4 count falls below 200 cells per µL. This is most consistent with:
- A. AIDS in an HIV-infected person ✓
- B. hepatitis B recovery
- C. an allergic reaction
- D. dengue haemorrhagic fever
Answer: A. AIDS in an HIV-infected person
Explanation: A very low CD4 count defines advanced HIV infection (AIDS) with opportunistic infections.

The other 25 questions

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Q6. In the lysogenic cycle of a bacteriophage, the phage DNA:
- A. integrates into the host chromosome as a prophage
- B. produces new phages immediately and lyses the cell
- C. is degraded at once
- D. remains as protein
Q7. Which sequence correctly describes the lytic cycle of T4 phage?
- A. Attachment → injection → synthesis → assembly → lysis
- B. Injection → attachment → lysis → synthesis
- C. Assembly → attachment → injection
- D. Lysis → assembly → attachment
Q8. The Hepatitis B vaccine is made from:
- A. recombinant HBsAg protein
- B. live attenuated virus
- C. whole inactivated virus particles only
- D. viral RNA
Q9. Dengue fever is transmitted by:
- A. Anopheles mosquitoes
- B. house flies
- C. Aedes mosquitoes
- D. Culex only
Q10. Viroids differ from viruses because viroids:
- A. have a capsid but no nucleic acid
- B. are infectious proteins
- C. lack a protein coat and consist of a short circular RNA
- D. contain DNA only
Q11. Prions cause diseases such as bovine spongiform encephalopathy because:
- A. they integrate into DNA
- B. they carry reverse transcriptase
- C. a misfolded protein induces normal proteins to misfold
- D. they produce toxins
Q12. A bacterium stains pink after Gram staining. Which statement explains this?
- A. Its DNA is stained pink
- B. It lacks a cell membrane
- C. A thin peptidoglycan layer fails to retain crystal violet when decolourised
- D. A thick peptidoglycan layer retains the dye
Q13. In bacterial conjugation, the DNA is transferred through:
- A. a sex pilus from F⁺ to F⁻ cell
- B. binary fission
- C. transformation of naked DNA
- D. a phage particle
Q14. A harmless bacterium acquires antibiotic resistance after taking up free DNA released by dead resistant cells. This process is:
- A. transformation
- B. transduction
- C. binary fission
- D. conjugation
Q15. Generalised transduction transfers bacterial genes by:
- A. naked DNA uptake
- B. spores
- C. direct contact through pili
- D. a bacteriophage carrying host DNA
Q16. A bacterial culture has 1000 cells and a generation time of 20 minutes. How many cells will be present after 2 hours, assuming no cell death?
- A. 12 000
- B. 6 000
- C. 64 000
- D. 32 000
Q17. In the standard growth curve, the phase in which the number of new cells equals the number dying is the:
- A. stationary phase
- B. log phase
- C. lag phase
- D. death phase
Q18. Endospore formation helps bacteria such as Bacillus anthracis to:
- A. survive heat, desiccation and chemicals
- B. reproduce faster
- C. fix nitrogen
- D. exchange plasmids
Q19. Nitrogen-fixing cyanobacteria such as Anabaena fix nitrogen in:
- A. akinetes only
- B. gas vesicles
- C. thylakoids of every cell
- D. heterocysts
Q20. Rhizobium and legumes form nodules in which the bacteria convert:
- A. atmospheric N₂ into ammonia
- B. ammonia into nitrate
- C. protein into urea
- D. nitrate into N₂
Q21. Chemolithotrophic bacteria such as Nitrosomonas obtain energy by oxidising:
- A. organic acids
- B. sunlight
- C. glucose
- D. ammonia
Q22. Which statement about archaea is correct?
- A. They are all pathogenic
- B. They have 80S ribosomes
- C. Their cell walls lack peptidoglycan
- D. They have a nuclear envelope
Q23. In Whittaker's five-kingdom system, a multicellular, heterotrophic organism with chitin walls that absorbs nutrients belongs to:
- A. Plantae
- B. Protista
- C. Fungi
- D. Animalia
Q24. Yeast reproduces asexually mainly by:
- A. fragmentation of hyphae
- B. conidia only
- C. budding
- D. binary fission
Q25. In Rhizopus, zygospores are formed by fusion of:
- A. a gamete and a zygote
- B. hyphae of opposite mating types
- C. spores from the same sporangium
- D. a sporangiospore and a conidium
Q26. Mycorrhizae benefit the plant mainly by:
- A. protecting leaves from light
- B. producing sugars
- C. fixing atmospheric nitrogen
- D. increasing absorption of water and phosphate
Q27. Penicillin, produced by Penicillium, acts by:
- A. blocking 70S ribosomes
- B. inhibiting the synthesis of bacterial cell wall peptidoglycan
- C. damaging the nucleus
- D. inhibiting DNA gyrase
Q28. Lysozyme in tears and saliva protects against bacteria by:
- A. blocking ribosomes
- B. hydrolysing the peptidoglycan of the cell wall
- C. digesting bacterial DNA
- D. neutralising toxins
Q29. Which protist causes malaria?
- A. Trypanosoma
- B. Giardia
- C. Plasmodium
- D. Entamoeba
Q30. Which of the following diseases is caused by a protozoan transmitted through contaminated water and causes amoebic dysentery?
- A. Vibrio cholerae
- B. Hepatitis A virus
- C. Entamoeba histolytica
- D. Salmonella typhi