DBT BET- Biotechnology Previous Questions

21. Which of the following plant hormones is synthesized from an amino acid precursor?
(A) Ethylene
(B) Auxins
(C) Cytokinin
(D) Abscisic acid
Ans: Auxins
22. Which one of the following is an example of structural chromosomal aberration?
(A) Edward’s syndrome
(B) Down’s syndrome
(C) Turner’s syndrome
(D) Cri-du-chat syndrome
Ans: Cri-du-chat syndrome
  • Karyotype :46,XY, del(5)(p25) 
  • Short arm deletion of 5
For more: Human Genetic Disorder
23. A mammalian cell has an outstretched double stranded DNA of 1.2 meter which duplicates in 4hrs. If it duplicates at the rate of 20μmeter/min, how many origins of replication are there in the DNA?
      (A) 2500
       (B) 250
       (C) 25
        (D) 1
Ans: 250
Length of dsDNA=1.2 m=1.2x106 um
Rate of duplication=20um per minute
Time taken for duplication (if there is single ori)= 1.2x106/20um=60000min=1000hrs
Actual time taken=4hrs
No. of ori required to complete duplication in 4 h=1000/4=250 origins
24. Which of the following cells secrete Eselectins?
(A) Eosinophils
(B) Endothelial cells
(C) Microglial cells
(D) Epithelial cells
Ans: Endothelial cells
  • The Selectin family is comprised of three members, E-Selectin, L-Selectin, and P-Selectin.
  • E-selectin (endothelial leukocyte adhesion molecule-1 (ELAM-1)is expressed on inflamed endothelial cells in response to treatment with inflammatory cytokines.
  • L-Selectin (Leukocyte Selectin)is expressed constitutively on a wide variety of leukocytes. Human P-Selectin (GMP-140, LECAM-3, PADGEM, CD62P) is expressed by activated platelets and endothelial cells.
25.'Weak calf syndrome' in pregnant cows at 80-125 days of gestation period is caused by
(A) BVD virus
(B) Pseudorabies virus
(C) IBR Virus
(D) MCF virus
Ans:Bovine Viral Diarrhea (BVD)Virus
26. Which of the following is/are selective media for Vibrio cholerae?
(A) Thayer –Martin medium
(B) Cefoxitin cycloserine fructoseagar
(C) Skirrow’s medium
(D) Thiosulfate-citrate-bile-sucrose agar
Ans:Thiosulfate-citrate-bile-sucrose agar
  • Thiosulfate-citrate-bile salts-sucrose agar - isolation of pathogenic vibrios.
  • Thayer-Martin Selective Agar -selective isolation of Neisseria species.
  • Cycloserine Cefoxitin Fructose Agar (CCFA) - isolation and identification of Clostridium.
  • Skirrow's medium - suitable for growing Campylobacter fetus and Brucella spp.
27. Which one of the following microscopic techniques is best suited to visualize the topology and distribution of transmembraneprotein of a cell membrane?
(A) Scanning electron microscopy
(B) Transmission electron microscopy
(C) Freeze-fracture electron microscopy
(D) Thin-section electron microscopy
Ans:C) Freeze fracture electron microscopy
28.Bovine keratitis is caused by
(A) Morexella bovis
(B) Bordetella pertosis
(C) Staphylococcus
(D) Bacteroides
Ans: Moraxella bovis
29. A novel type II restriction enzyme has been isolated from a thermophilic bacteria. This restriction endonuclease recognizes 5’ATAANNNTTAT3’ (N= any nucleotide) and cuts after third ‘A’ in the above sequence. What is the fate of DNA after restriction digestion ?
(A) a 3 nucleotide long 5´ overhang
(B) a 7 nucleotide long 5´ overhang
(C) a 4 nucleotide long 5´ overhang
(D) a 3 nucleotide long 3´ overhang
Ans: is (A) a 3 nucleotide long 5´ overhang.
For answering this question, we should know exactly what is Type II restriction enzyme?
  • Only Type II restriction enzymes are used in rDNA technology as it can cut DNA at specific sequences called restriction sites or recognition sequences.
  • Recognition sequences of type II restriction enzymes are palindromes with rotational symmetry. This point should be in mind to answer this question
  • Recognition sequence in the question is 5’ATAA-NNNTTAT3’ cleaves after 3rd A.
  • Then the complementary sequence is     3’TATT NNN-AATA5’ (-)restriction site
  • Upon restriction we get the sequence as 5’ATAA          and NNNTTAT3’
         3’TATT NNN AATA5’
  • Overhang means single stranded unpaired region.
30. Xenopsylla cheopis is the vector for
(A) Indian tick typus
(B) Epidemic typus
(C) Plague
(D) Kala azar
Ans: Plague
Male Xenopsylla cheopis -This flea is the primary vector of plague.
31. Elevation of intracellular inositol triphosphate (IP3) results in the release of Ca2+ from which of the following organelles?
(A) Mitochondria
(B) Smooth endoplasmic reticulum
(C) Peroxisome
(D) Golgi-complex
Ans: (B) Smooth endoplasmic reticulum
  • Second messengers include IP3, DAG, cAMP, cGMP
32. Testosterone hormone necessary for spermatogenesis is secreted by
(A) sertoli cells
(B) leydig cells
(C) spermatozoa
(D) cowpers gland
Ans: (B) leydig cells
33. When Hfr strain of E. coli is crossed with F- strain, recombinants obtained are
(A) always F+
(B) always HFr+
(C) rarely F+
(D) rarely HFr+
Ans: rarely F+
  • In bacteria, transfer of genetic material (DNA) from one bacterium (donor) to another (recipient) takes place through three methods i.e., Transformation, Transduction and Conjugation.
  • Conjugation was discovered in 1942 by Lederberg and Tatum.
  • During conjugation DNA is transferred from donor cell to a recipient cell through a conjugation canal formed between them.
  • The donor cells posses a small circular DNA (plasmid) called F factor ( fertility factor or sex factor). The F factor can exist in two states: the autonomous states (F+)and the integrated state(Hfr). Bacteria without F factor is refererred as F-.
  • F+x F- = F+, F-  becomes F+
  • Hfr x F- =F- remain F- as usually F factor may not be transferred, where as some bacterial genes of Hfr may integrate into the F- genome during conjugation.
34.The mouse model for type II diabetes mellitus is
(A) NZB mouse
(B) SCID mouse
(C) Nude mouse
(D) NOD mouse
Ans: NOD mouse
  • NZB Mouse as a Model for Chronic Lymphocytic Leukemia
  • Nude mouse - immuno deficient mice
  • NOD: The mouse model for type Idiabetes mellitus
  • Nagoya-Shibata-Yasuda (NSY) specifically the mouse model for type II diabetes mellitus
35. In which of the following cases, the enzyme substrate complex is irreversible in nature?
(A) Competitive inhibition
(B) Non-competitive inhibition
(C) Un-competitive inhibition
(D) Both competitive and non-competitive inhibition
Ans: Un-competitive inhibition
36. Replication of papillomavirus is restricted to
(A) epithelial cells
(B) nerve cells
(C) fibroblasts
(D) reticulo-endothelial cells
Ans: epithelial cells
37. Which of the following is a lipid with a signal transducing activity?
(A) Phosphatidyl serine
(B) Phosphatidyl ethanolamine5
(C) Phosphatidyl inositol 4,5-bisphosphate
(D) Phospholipase A2
Ans:Phosphatidyl inositol 4,5-bisphosphate
38. Which one of the following techniques is used for the evaluation of phylogenetic trees?
(A) Null hypothesis
(B) Bootstrapping
(C) Chi-square
(D) Probability
Ans: Bootstrapping
39. NiceProt is
(A) Protein sequence database
(B) Derived Protein database
(C) Protein sequence view
(D) Nucleotide sequence view
Ans:Protein sequence view
NiceProt View of Swiss-Prot
40. Which of the following chemotherapeutic drugs has neurotoxicity?
(A) Vincristine
(B) Cyclophosphamide
(C) Anthracyclines
(D) Adriamycin
  • Anthracyclines attack cancer cells by multiple mechanisms, inhibiting replication and damaging cells in ways that promote cell death.
  • Cyclophosphamide (CP), an alkylating agent is one of the widely used cytostatic drugs.
  • Adriamycin (Doxorubicin) is an anthracycline antibiotic isolated from streptomyces peucetius. Adriamycin prevents DNA replication.
For More: Biotechnology MCQs/ Biotechnology Notes/ DBT BET Questions
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