11. Who among the following first synthesized “gene” in a laboratory ?
[A] Arthur kornberg
[B] Hargobind Khorana
[C] Gregor Mendel
[D] Watson and crick
Show Answer
Correct Answer: B [Hargobind Khorana]
Notes:
Hargobind Khorana first synthesized “gene” in a laboratory. Hargobind Khorana was an Indian American biochemist who shared the 1968 Nobel Prize for Physiology or Medicine with Marshall W. Nirenberg and Robert W.
12. Pest-resistant cotton commonly known as ‘Bt-Cotton’ is genetically engineered by inserting a gene from a:
[A] Bacterium
[B] Virus
[C] Microalgae
[D] Protist
Show Answer
Correct Answer: A [Bacterium]
Notes:
Bt cotton is an insect-resistant transgenic crop designed to combat the bullworm. Bt is a soil bacterium containing Cry genes that encode crystal proteins which are fatal to some Lepidopteran caterpillars when ingested.
13. Which of the following cells are closely associated and interacting with guard cells?
[A] Transfusion tissue
[B] Complementary cells
[C] Subsidiary cells
[D] Hypodermal cells
Show Answer
Correct Answer: C [Subsidiary cells]
Notes:
Subsidiary cells are the accessory cells to guard cells in the epidermis of plants. Two or four subsidiary cells are found surrounding the pair of guard cells. Subsidiary cells do not consist of chloroplasts. They provide support for the functioning of guard cells in the epidermis.
14. In typhoid which of the following drugs is administered? (UPSC Prelims 1983)
[A] Chloromycetin
[B] Penicillin
[C] Sulphonamide
[D] Tetracycline
Show Answer
Correct Answer: A [Chloromycetin]
Notes:
Chloromycetin or Chloramphenicol is the drug of choice in the treatment of this disease. It has been the antibiotic of choice for patients with typhoid fever for more than 30 years, although ampicillin and cotrimoxazole are also used.
15. Why man cannot digest cellulose whereas cows can do so? (UPSC Prelims 1992)
[A] Their gut contains certain bacteria capable of digesting cellulose
[B] They have a many-chambered stomach
[C] They have efficient grinding molars
[D] They produce enzyme cellulose which can digest cellulose
Show Answer
Correct Answer: A [Their gut contains certain bacteria capable of digesting cellulose]
Notes:
Unlike cows for example don’t have the necessary bacteria in their intestines that make the enzymes necessary to breakdown the 1-4 beta glucose bonds. So we cannot break down cellulose into its constituent glucose molecules as we do with starch.
16. At which of the following ages Rennin and lactase, disappear in the human body? (UPSC Prelims 1994)
[A] two
[B] three
[C] five
[D] eight
Show Answer
Correct Answer: A [two]
Notes:
By the age of two, the rennin and lactase enzymes start disappearing. However, these enzymes completely disappear by the age of eight in humans. After, this the stomach of person becomes mature enough to produce pepsin to digest the food.
17. What is the average fat content of buffalo milk? (UPSC Prelims 1997)
[A] 7.2%
[B] 4.5%
[C] 9.0%
[D] 10.0%
Show Answer
Correct Answer: A [7.2%]
Notes:
Average fat content in buffalo milk is 7.2% and average fat content in cow milk is 4.4%. As per the nutrient components, buffalo milk contains all the nutrients in higher proportion than cow’s milk.
18. Which one of the following statements is correct? (UPSC Prelims 2002)
[A] Prions are the smallest free-living cells
[B] The cell wall of Mycoplasmas is made up of amino sugars
[C] Viroids consist of a single-stranded RNA molecule
[D] Rickettsias lack cell wall
Show Answer
Correct Answer: C [Viroids consist of a single-stranded RNA molecule]
Notes:
Viroids are the smallest infectious pathogens known. They are composed solely of a short strand of circular, single-stranded RNA that has no protein coating. All known viroids are inhabitants of higher plants, in which most cause diseases, ranging in economic importance.
19. What term is used for a gene that exhibits multiple effects?
[A] Pleiotropism
[B] Multitropism
[C] Complementary
[D] Allele
Show Answer
Correct Answer: A [Pleiotropism]
Notes:
Pleiotropism describes the genetic effect of a single gene on multiple phenotypic traits. A classic example of pleiotropy is phenylketonuria, a human disease that affects multiple systems but is caused by one gene defect. The underlying mechanism is that the gene codes for a product that is, for example, used by various cells, or has a signaling function on various targets.
20. Which blood group is referred to as universal recipient?
[A] AB +ve
[B] AB -ve
[C] O +ve
[D] O -ve
Show Answer
Correct Answer: A [AB +ve]
Notes:
Persons with AB +ve blood group are called as universal recipients as they can get blood from persons with any of the blood groups. AB -ve cannot be regarded as universal donor as it cannot accept blood from persons with Rh factor.
