Questions and Answers

Thermal death of microorganisms in the liquid medium follows first order kinetics. If the initial cell concentration in the fermentation medium is 10⁸ cells / ml and the final acceptable contamination level is 10⁻³ cells, for how long should 1m³ medium be treated at temperature of 120° (thermal deactivation rate constant = 0.23 / min) to achieve acceptable load?
(A) 48 min
(B) 11 min
(C) 110 min
(D) 20 min

Determine the correctness or otherwise of the following Assertion (a) and the Reason (r)
Assertion: Cytoplasmic male sterility (cms) is invariably due to defect(s) in mitochondrial function.
Reason: cms can be overcome by pollinating a fertility restoring (Rf) plant with pollen from a non cms plant.
(A) both (a) and (r) are true and (r) is the correct reason for (a)
(B) both (a) and (r) are true and (r) is not the correct reason for (a)
(C) (a) is false but (r) is true
(D) (a) is true but (r) is false

Match the products in Group I with the microbial cultures in Group II used for their industrial production
Group I:
P. Gluconic acid
Q. L-Lysine
R. Dextran
S. Cellulase
Group II:
1. Leuconostoc mesenteroids
2. Aspergillus niger
3. Brevibacterium flavum
4. Trichoderma reesei
(A) P-2, Q-1, R-3, S-4
(B) P-1, Q-3, R-4, S-2
(C) P-2, Q-3, R-1, S-4
(D) P-3, Q-2, R-4, S-1

A cell has five molecules of a rare mRNA. Each cell contains 4 × 10⁵ mRNA molecules. How many clones one will need to screen to have 99% probability of finding at least one recombinant cDNA of the rare mRNA, after making cDNA library from such cell?
(A) 4.50 × 10⁵
(B) 3.50 × 10⁵
(C) 4.20 × 10⁵
(D) 4.05 × 10⁵

Receptor R is over expressed in CHO cells and analysed for expression. 6 × 10⁷ cells were incubated with its radioactive ligand (specific activity 100 counts per picomole). If the total counts present in cell pellet was 1000 cpm, the average number of receptors R per cell is (assume complete saturation of receptors with ligand and one ligand binds to one receptor)
(A) 10⁴
(B) 10⁵
(C) 10⁶
(D) 10⁷

The dissociation constant Kd for ligand binding to the receptor is 10⁻⁷ M. The concentration of ligand required for occupying 10% of receptors is
(A) 10⁻⁶ M
(B) 10⁻⁷ M
(C) 10⁻⁸ M
(D) 10⁻⁹ M

Dizygotic twins are connected to a single placenta during their embryonic development. These twins
(A) have identical MHC haplotypes
(B) have identical TH cells
(C) have identical T cells
(D) can accept grafts from each other (both (A) and (B))

A mutant Gα protein with increased GTPase activity would
(A) not bind to GTP
(B) not bind to GDP
(C) show increased signaling
(D) show decreased signaling

Match Group I with Group II
Group I:
P. Staphylococcus aureus
Q. Candida albicans
R. Mycobacterium tuberculosis
S. Lactobacillus lactis
Group II:
1. Biofilms
2. Bacteriocins
3. Methicillin resistance
4. Isoniazid
(A) P-1, Q-4, R-2, S-3
(B) P-2, Q-3, R-1, S-4
(C) P-3, Q-1, R-4, S-2
(D) P-1, Q-2, R-4, S-3

Match the items in Group I with Group II
Group I (Vectors):
P. λ phage
Q. Bacterial Artificial Chromosomes (BACs)
R. P1 derived Artificial Chromosomes (PACs)
S. λ cosmid
Group II (Maximum DNA packaging):
1. 35-45 kb
2. 100-300 kb
3. ≤ 300 kb
4. 5 – 25 kb
(A) P-3, Q-4, R-1, S-2
(B) P-1, Q-3, R-2, S-4
(C) P-4, Q-3, R-2, S-1
(D) P-1, Q-2, R-3, S-4