MCQs Gate Life Science 

1. Humpty Dumpty sits on a wall evry day while having lunch. The wall sometimes breaks. A person sitting on the wall falls if the wall breaks. Which one of the statements below is logically valid and can be inferred from the above sentences?
(a) Humpty Dumpty always falls while having lunch
(b) Humpty Dumpty does not falls while having lunch
(c) Humpty Dumpty never falls during dinner
(d) When Humpty Dumpty does not sit on the wall, the wall does not break.
Ans. (b)
2. The following question presents a sentence, part of which is underlined. Beneath the sentence you find four ways of phrasing the underline part. Following the requirements of the standard written English, select the answer that produces the most effective sentence. Tuberculosis, together with its effects, ranks one of the leading causes of death in India.
(a) ranks as one of the leading causes of death
(b) rank as one of  the leading causes of death
(c) has the rank as one of  the leading causes of death
(d) are one of the leading causes of death
Ans. (a)
3. Read the following paragraph and choose the correct statement. Climate change has reduced human security and threatened human well being. An ignored reality of human progress is that human security largely depends upon environmental security. But on the contrary, human progress seems contradictory to environmental security. To keep up both at the required level is a challenge to be addressed by one and all. One of the ways to curb the climate change may be suitable scientific innovations, while the other may be the Gandhian perspective on small scale progress with focus on sustainability.
(a) Human progress and security are positively associated with environmental security
(b) Human progress is contradictory to environmental security
(c) Human security is contradictory to environmental security
(d) Human progress depends upon environmental security
Ans. (a)
4. The number of possible enantiomeric pair(s) in HOOC−CH(OH)−CH(OH)−COOH is________
(a) 2                             
(b) 1
(c) 3                             
(d) 4
Ans. (b)
5. The molecule having net ‘non-zero dipole moment’ is
(a) CCl4                        
(b) NF3                         
(c) CO2                        
(d) BCl3       
 Ans. (b)
6. If the radius of first Bohr orbit is 0.53Å, then the radius of the third Bohr orbit is
(a) 2.12 Å                     
(b) 4.77 Å           
(c) 1.59 Å                       
(d) 3.18 Å
Ans. (b)
7. Which one of the following amino acid substitutions is likely to cause the largest change in protein conformation?
(a) Phe → Ile                
(b) Ser → Thr
(c)  Gln → Tyr               
(d) Glu → Val   
Ans. (d)
8. Ribulose-5-phosphate epimerase is involved in which one of the following processes?
(a) Glycolysis               
(b) TCA cycle
(c)Glycosylation           
(d) Pentose phosphate pathway
Ans. (d)
9. The formation of a carbocation, also called an oxonium ion, occurs during the reaction catalyzed by
(a) aldolase                  
(b) lysozyme    
(c) ribonuclease A        
(d)   carboxypeptidase
Ans. (b)
10. A closed circular B-DNA of 4000 base pairs is negatively supercoiled by introduction of 4 writhes. The super helical density of the resultant DNA molecule will be _________
(a) -0.0105                    
(b) -0.0101
(c) -0.0106                    
(d) -0.0104
Ans. (a)
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