Questions and Answers

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

The turnover numbers for the enzymes, E1 and E2 are 150 s⁻¹ and 15 s⁻¹ respectively. This means
(A) E1 binds to its substrate with higher affinity than E2
(B) The velocity of reactions catalyzed by E1 and E2 at their respective saturating substrate concentrations could be equal, if concentration of E2 used is 10 times that of E1
(C) The velocity of E1 catalyzed reaction is always greater than that of E2
(D) The velocity of E1 catalyzed reaction at a particular enzyme concentration and saturating substrate concentration is lower than that of E2 catalyzed reaction under the same conditions

Consider the following statements.
I. T4 DNA ligase can catalyze blunt end ligation more efficiently than E.coli DNA ligase
II. The ligation efficiency of T4 DNA ligase can be increased with PEG and ficoll.
(A) only I is true
(B) both I and II are true
(C) only II is true
(D) I is true and II is false

Match the promoters listed in Group I with the tissues listed in Group II
Group I:
P. α-Amylase
Q. Glutenin
R. Phaseollin
S. Patatin
Group II:
1. Endosperm
2. Tuber
3. Aleurone
4. Cotyledon
(A) P-3, Q-1, R-4, S-2
(B) P-3, Q-4, R-1, S-2
(C) P-4, Q-2, R-1, S-3
(D) P-1, Q-3, R-2, S-4