581: One of your friends is in hospital and you want to see him. You are safest if he is suffering from:
(a) Mumps
(b) TB
(c) Small pox
(d) Typhoid
582: Which of the following statements is/are correct?
1. Viruses lack enzymes necessary for the generation of energy.
2. Viruses can be cultured in any synthetic medium.
3. Viruses are transmitted from one organism to another by biological vectors only.
Select the correct answer using the codes given below.
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Explanation:
Viruses do not have energy generating system and do not possess many of the enzymes necessary for making nucleic acid.
Viruses do not replicate by dividing their component parts and then splitting into two (binary fission) as bacteria do.
So only statement 1 is correct.
583: With reference to the recent developments in science, which one of the following statements is not correct?
(a) Functional chromosomes can be created by joining segments of DNA taken from cells of different species.
(b) Pieces of artificial functional DNA can be created in laboratories.
(c) A piece of DNA taken out from an animal cell can be made to replicate outside a living cell in a laboratory.
(d) Cells taken out from plasma and animals can be made to undergo cell division in laboratory petri dishes.
Explanation:
In a major step toward creating artificial life, US researchers have developed a living organism that incorporates both natural and artificial DNA and is capable of creating entirely new, synthetic proteins. Hence, option (b) is correct. A wide variety of double-stranded DNA templates are replicated extensively in an in vitro DNA replication system containing the purified proteins specified by seven T4 bacteriophage DNA replication genes (32, 41, 43, 44, 62, 45, and 61). Hence, option (c ) is correct. Through micropropagation plant can be developed in laboratory and chlamydomnas cells can be replicated in culture through light variations. Hence, option (d) is correct.
Source: http://ncert.nic.in/ncerts/l/lebo109.pdf
584: Which one of the following does not contain silver?
(a) German silver
(b) Lunar caustic
(c) Horn Silver
(d) Ruby silver
Explanation:
German Silver comprises of Cu, Zn and Ni used in utensils are arts.
585: Which of the following leaf modifications occurs/occur in desert areas to inhibit water loss?
1. Hard and waxy leaves
2. Tiny leaves or no leaves
3. Thorns instead of leaves
Select the correct answer using the codes given below.
(a) 1 and 2 only
(b) 1 and 3 only
(c) 2 only
(d) 1, 2 and 3
Explanation:
The vegetation of hot desert climate is xerophytic type which has special characteristics to withstand very high rate of evaporation. They have long roots, thick barks, hard & waxy leaves, thorns and little leaves or no leaves.
See NCERT Geography book of 9th std. on page 46.
Hence all the statements 1,2 and 3 are correct.