List of top Questions asked in CBSE CLASS XII

Differentiate between grazing food chain and detritus food chain.
Suggest how a virus-free healthy plant can be obtained from a diseased sugarcane plant.
In order to force bacteria to take up the recombinant DNA, they must be made competent. Explain how it can be achieved.
Mention the functions of each of the following: (i) Tassels of Corn Cob, (ii) Scutellum
Farmers prefer apomictic seeds over hybrid seeds. Give any two reasons.
Draw a labelled diagram of the embryonic stage that gets implanted in the human uterus. State the functions of two labelled parts.
Bt-toxin genes have been expressed in plants in order to provide resistance against:
• [(i)] lepidopterans and fungi
• [(ii)] animals and bacteria
• [(iii)] coleopterans and dipterans
• [(iv)] lepidopterans
Assertion (A): Genetically modified microbes help in crop protection.
Reason (R): Bacillus thuringiensis (Bt) bacteria control insects by producing prototoxins.
Assertion (A): Repetitive sequences make up a very large portion of human genome.
Reason (R): Repetitive sequences do not have direct coding functions in the genome.
Assertion (A): The endometrium undergoes cyclic changes during the menstrual cycle.
Reason (R): Perimetrium contracts strongly during delivery of the baby.
Assertion (A): Trichoderma species are free living fungi that are very common in the root ecosystems.
Reason (R): They are effective bio-control agents of several plant pathogens.
According to IUCN, some of the extinctions include:
• [(i)] Dodo
• [(ii)] Indian gazelle
• [(iii)] Thylacine
• [(iv)] Steller’s Sea Cow
Monascus purpureus is a yeast used commercially in the production of which one of the following?
Select the odd option in the context of convergent evolution.
Given below is the restriction site of a restriction endonuclease Pst I and the cleavage sites on a DNA molecule.
Choose the option that gives the correct resultant fragments.
Which of the following ecosystems is most productive in terms of net primary productivity?
The cells of endosperm have 24 chromosomes. What will be the number of chromosomes in the gametes?
S is the stimulant of central nervous system and interferes with the transport of T, a neurotransmitter. Identify S and T and choose the correct option.
During different phases of menstrual cycle, hormones are secreted. Choose the option showing the correct sequence of hormones.
Arrange the following in the correct sequence of their evolution and select the correct option:
• [(i)] Seaweed
• [(ii)] Invertebrates
• [(iii)] Jawless fish
A DNA molecule is 160 base pairs long. It has 30% Guanine. How many Adenine bases are present in this DNA molecule?
In a human female, menstrual cycle of 28 days is represented by the diagram given below (Phase I: Days 1--5, Phase II: Days 6--13, Phase III: Days 15--28). Select the correct statement related with this diagram.
Pahari miniature reflects the freedom the artists were given to show diversity of artistic expression within miniature style. Choose one of the paintings given below and answer:
(i) Write the name of the artist and the sub-school of painting.
(ii) Explain any two characteristics of the sub-school.
(a) Krishna with Gopis
OR
(b) Nand, Yashoda and Krishna with kinsmen going to Vrindavan
State any three points of significance of Principles of Management.
A square loop of side 0.50 m is placed in a uniform magnetic field of 0.4 T perpendicular to the plane of the loop. The loop is rotated through an angle of 60° in 0.2 s. The value of emf induced in the loop will be: