NEET WEEKLY TEST BIOLOGY (SDA KHATLA) (19.09.2026)

BIOLOGY

1. Consider the following statements about pBR322:
1. It contains an origin of replication.
2. It contains genes for resistance to ampicillin and tetracycline.
3. It is a naturally occurring plasmid.
4. Its selectable markers help identify transformants.
Which are correct?

1. 1 and 3
2. 1, 2 and 4
3. 2, 3 and
4 4. 1, 2, 3 and 4

2. Which combination correctly represents the source → hormone → major target?

1. Anterior pituitary → ACTH → adrenal cortex
2. Posterior pituitary → TSH → thyroid
3. Anterior pituitary → ADH → kidney
4. Hypothalamus → ACTH → adrenal cortex

3. Consider the following statements about PCR:
1. Primers provide a free 3′-OH group for DNA synthesis.
2. DNA polymerase synthesizes DNA in the 5′ → 3′ direction.
3. Both primers determine the boundaries of the amplified region.
4. Restriction endonuclease is essential for every PCR reaction.
Which are correct?

1. 1 and 2 only
2. 1, 2 and 3 only
3. 2, 3 and 4 only
4. 1, 2, 3 and 4

4. A person has abnormally low levels of T₃ and T₄ in blood. If the thyroid gland itself is functioning normally, which combination would most likely be observed?

1. ↓ TRH, ↓ TSH
2. ↑ TRH, ↑ TSH
3. ↑ TRH, ↓ TSH
4. ↓ TRH, ↑ TSH

5. Consider the following statements:
Statement I: Insertion of foreign DNA into an antibiotic-resistance gene can inactivate that gene.
Statement II: This property can be used to distinguish recombinant plasmids from non-recombinant plasmids.

1. Both statements are correct, and II correctly explains I
2. Both statements are correct, but II does not explain I
3. I is correct but II is incorrect
4. Both are incorrect

6. Assertion (A): ADH is considered a posterior pituitary hormone.
    Reason (R): ADH is synthesized by cells of the posterior pituitary.

1. Both A and R are true, and R correctly explains A
2. Both A and R are true, but R does not explain A
3. A is true but R is false
4. A is false but R is true

7. A cloning vector should have a unique restriction site mainly because:

1. It allows replication of the vector
2. It permits insertion of foreign DNA at a specific location
3. It provides antibiotic resistance
4. It increases the size of the host genome

8. Consider the following statements:
1. GH is secreted by the anterior pituitary.
2. ADH is synthesized in the hypothalamus.
3. ADH is released from the posterior pituitary.
4. Oxytocin is synthesized by the posterior pituitary.
Which are correct?

1. 1, 2 and 3 only
2. 1 and 2 only
3. 1, 3 and 4 only
4. 2, 3 and 4 only

9. Consider the following steps:
1. Isolation of DNA
2. Separation of DNA fragments
3. Restriction digestion
4. Ligation of desired DNA fragment into vector
5. Introduction into host 
Which sequence is correct?

1. 1 → 2 → 3 → 4 → 5
2. 2 → 1 → 4 → 3 → 5
3. 1 → 3 → 2 → 4 → 5
4. 3 → 1 → 2 → 5 → 4

10. Assertion (A): The same restriction enzyme is generally used to cut the vector and foreign DNA during recombinant DNA formation.
Reason (R): This produces compatible ends that can base-pair with each other.

1. Both A and R are true, and R is the correct explanation
2. Both A and R are true, but R is not the correct explanation
3. A is true, R is false
4. A is false, R is true

11. Which sequence correctly represents the hypothalamic–pituitary–thyroid axis?

1. Hypothalamus → TSH → TRH → Thyroid
2. Hypothalamus → TRH → Anterior pituitary → TSH → Thyroid
3. Hypothalamus → T3 → Pituitary → TSH
4. Hypothalamus → TSH → Thyroid → TRH

12. Assertion (A): Electroporation can be used for gene transfer into both plant and animal cells.
      Reason (R): Divalent cation increases the permeability of the cell membrane.

1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, but R is not the correct explanation of A
3. A is true, but R is false
4. Both A and R are false

13. A woman has normal milk production but impaired milk ejection. Which hormone is most likely deficient?

1. Luteotropin
2. Oxytocin
3. FSH
4. GH

14. Which technique is particularly useful for introducing DNA into an individual animal cell?

1. Microinjection
2. Biolistics
3. Ti plasmid
4. Calcium phosphate precipitation

15. In the biolistic method, foreign DNA is coated onto:

1. Liposomes
2. Viral capsids
3. Calcium ions
4. Gold or tungsten particles

16. In males, LH stimulates:

1. Sertoli cells to produce sperm directly
2. Leydig cells to produce androgens
3. Thyroid cells to produce thyroxine
4. Adrenal medulla to release adrenaline

17. Which of the following represents the correct order in production of a recombinant protein using bacterial cells?

1. Purification → transformation → selection → expression
2. Expression → transformation → purification → selection
3. Transformation → selection → expression → purification
4. Selection → purification → transformation → expression

18. A very important distinction regarding posterior pituitary hormones is that:

1. They are synthesized in the posterior pituitary but stored in the hypothalamus
2. They are synthesized and released exclusively by the posterior pituitary
3. They are synthesized in the anterior pituitary and stored in the hypothalamus
4. They are synthesized in the hypothalamus and released from the posterior pituitary

19. Assertion (A): Selectable markers are important in recombinant DNA technology.
      Reason (R): They help identify or select cells that have received the vector or recombinant DNA.

1. Both A and R are true, and R correctly explains A
2. Both A and R are true, but R does not explain A
3. A is true, R is false
4. A is false, R is true

20. Which combination contains only hormones of Adenohypophysis?

1. GH, PRL, TSH, ACTH
2. ADH, oxytocin, GH, TSH
3. Oxytocin, PRL, ACTH, FSH
4. ADH, GH, LH, TSH

21. A bacterial culture contains three types of cells:
Type I: non-transformed cells
Type II: cells containing non-recombinant pBR322
Type III: cells containing recombinant pBR322 in which tetR has been disrupted
After plating separately on:
P = ampicillin
Q = tetracycline
R = ampicillin + tetracycline
Which result is expected?

1. Type I grows on P, Q and R
2. Type II grows on P and Q but not R
3. Type III grows on P but not Q or R
4. Type II and III both grow on R

22. Excess secretion of growth hormone after maturation causes:

1. Gigantism
2. Dwarfism
3. Acromegaly
4. Myxoedema

23. A DNA sample contains fragments of 200 bp, 500 bp, 1000 bp and 2000 bp. After electrophoresis, which fragment is expected to migrate farthest from the wells?

1. 2000 bp
2. 1000 bp
3. 500 bp
4. 200 bp

24. The descending limb of Henle is highly permeable to water but relatively less permeable to electrolytes. As tubular fluid moves deeper into the medulla:

1. Water enters the tubule and tubular fluid becomes dilute
2. Water leaves the tubule and tubular fluid becomes concentrated
3. NaCl enters and tubular fluid becomes dilute
4. Both water and NaCl leave equally

25. Consider the following statements:
1. Electrophoresis separates DNA fragments based on their movement through a gel under an electric field.
2. DNA fragments of the same size generally migrate similarly under identical conditions.
3. The smallest DNA fragment always remains closest to the well.
4. A DNA ladder can be used to estimate the size of separated fragments.

1. 1 and 2 only
2. 1, 2 and 4 only
3. 2 and 3 only
4. 1, 3 and 4 only

26. Consider the following statements about the collecting duct:
1. It participates in determining the final concentration of urine.
2. Its water permeability is influenced by ADH.
3. It is completely impermeable to water under all conditions.
4. It contributes to the concentration of urine.
Correct statements are:

1. 1, 2 and 4 only
2. 1 and 2 only
3. 2 and 3 only
4. 1, 2, 3 and 4

27. Regarding the DNA staining step:
1. DNA bands may be visualised after staining.
2. Ethidium bromide is a commonly discussed DNA stain.
3. DNA bands can be visualised using suitable UV illumination after staining with a fluorescent dye.
4. Staining is responsible for separating DNA fragments according to size.

1. 1, 2 and 3 only
2. 1 and 2 only
3. 2, 3 and 4 only
4. 1 and 4 only

28. The pituitary gland is anatomically connected to the hypothalamus by:

1. Corpus callosum
2. Infundibulum
3. Medulla oblongata
4. Spinal cord

29. Which of the following represents a DNA palindrome?

1. 5′-GGAACC-3′
3′-CCTTGG-5′
2. 5′-ATGCGA-3′
3′-TACGCT-5′
3. 5′-GAATTC-3′
3′-CTTAAG-5′
4. 5′-AACCGG-3′
3′-TTGGCC-5′

30. Consider the following statements:
1. The PCT is highly efficient in reabsorbing water and electrolytes.
2. Nearly all glucose and amino acids are normally reabsorbed in the PCT.
3. The ascending limb of Henle is highly permeable to water.
4. The descending limb is permeable to water.
Which statements are correct?


1. 1 and 2 only
2. 1, 2 and 4 only
3. 2 and 3 only
4. 1, 2, 3 and 4

31. A person drinks a very large amount of water. Which response is most appropriate?

1. Increased ADH secretion
2. Increased water reabsorption
3. Increased aldosterone secretion
4. Decreased ADH secretion

32. Which statement is incorrect regarding restriction endonucleases?

1. They are obtained from bacteria.
2. They provide protection against invading foreign DNA.
3. They recognize specific nucleotide sequences.
4. They randomly degrade the entire DNA molecule.

33. Atrial natriuretic factor (ANF) generally:

1. Increases blood pressure
2. Promotes sodium retention
3. Opposes the action of RAAS
4. Stimulates renin secretion

34. The number of copies of a plasmid inside a bacterial cell is primarily influenced by its:

1. Selectable marker
2. Origin of replication
3. Restriction site
4. Foreign DNA

35. ADH increases water reabsorption mainly by increasing water permeability of:

1. Distal tubule and collecting duct
2. PCT only
3. Bowman’s capsule
4. Glomerulus

36. Taq polymerase is preferred in PCR because it:

1. Can synthesize RNA
2. Cuts DNA at palindromic sequences
3. Joins DNA fragments
4. Remains active after repeated exposure to high temperatures

37. Match:

Codes:

1. A-2, B-1, C-3, D-4
2. A-1, B-2, C-4, D-3
3. A-2, B-3, C-1, D-4
4. A-1, B-4, C-3, D-2

38. Which structure is primarily responsible for creating the osmotic gradient in the renal medulla?

1. PCT only
2. Bowman’s capsule
3. Loop of Henle
4. Ureter

39. DNA fragment has the sequence:
5′–GAATTC–3′
3′–CTTAAG–5′
If it is treated with EcoRI, the product will have:

1. Blunt ends
2. 3′ sticky ends
3. 5′ sticky ends
4. No cleavage because EcoRI recognises RNA

40. Why is the osmolarity of the renal medulla higher than that of the cortex?

1. Due to only active transport of glucose
2. Due to the counter-current mechanism and accumulation of solutes
3. Due to filtration of proteins
4. Due to complete absence of blood vessels in the medulla

41. In blue-white screening using lacZ, a recombinant plasmid generally produces:

1. Blue colonies because β-galactosidase is active
2. White colonies because insertion disrupts lacZ
3. Blue colonies because the antibiotic resistance gene is disrupted
4. White colonies because the plasmid cannot replicate

42. Which of the following correctly describes the descending limb of the loop of Henle?

1. Impermeable to water and permeable to electrolytes
2. Highly permeable to water
3. Actively transports NaCl out of the tubule
4. Completely impermeable to water

43. The PCT contributes to maintenance of acid-base balance mainly by:

1. Secreting H⁺ and NH₃ and reabsorbing HCO₃⁻
2. Secreting HCO₃⁻ and reabsorbing H⁺
3. Secreting only NH₃
4. Reabsorbing only H⁺

44. If the initial PCR reaction contains one double-stranded DNA molecule, theoretically how many double-stranded DNA molecules are present after 5 cycles, assuming 100% efficiency?

1. 10
2. 16
3. 32
4. 64

45. Which of the following animals is correctly matched with its principal nitrogenous excretory product?

1. Humans — Ammonia
2. Birds — Urea
3. Reptiles — Uric acid
4. Aquatic bony fishes — Uric acid