List of top Questions asked in CBSE CLASS XII

How are morphine and heroin related? Mention their effect on the human body.
Assertion (A): When the two genes in a dihybrid cross are situated on the same chromosome, the proportion of parental gene combinations is much higher than non-parental type.
Reason (R): Higher parental gene combinations can be attributed to crossing over between two genes.
How many pollen grains and ovules are likely to be formed in the anther and ovary of an angiosperm bearing 50 microspore mother cells and 50 megaspore mother cells respectively?
RNA interference (RNAi) helps in making tobacco-plant resistant to a nematode (\textit{Meloidogyne incognita}). Choose the correct option that shows how RNAi is achieved:
Assertion (A): A bioreactor provides the optimal conditions for achieving the desired product by providing optimum growth conditions.
Reason (R): The most commonly used bioreactors are of stirring type.
Evolution of modern man involves the following man-like primates. Choose the correct series of human evolution:
Assertion (A): One of the properties of genetic code is degeneracy.
Reason (R): Some amino acids can be coded by more than one codon.
Assertion (A): Saheli is the World’s first non-steroidal oral contraceptive pill.
Reason (R): It has been developed by National Institute of Immunology, New Delhi.
The sequence of nitrogenous bases in a segment of a coding strand of DNA is
5' – AATGCTAGGCAC – 3'.
Choose the option that shows the correct sequence of nitrogenous bases in the mRNA transcribed by the DNA.
Match the following items of Column-I with that of Column-II:
Column-IColumn-II
(a) Trophoblast(iv) Outer layer of blastocyst
(b) Implantation(i) Embedding of blastocyst in the endometrium
(c) Inner cell mass(ii) Group of cells that would differentiate as embryo
(d) Morula(iii) Embryo with 8–16 blastomeres
Choose the option that matches Column-I with Column-II correctly:
Transplantation of tissues/organs to some patients often fails due to rejection by the body of the patient. Which type of immune response is responsible for such rejections?
GEAC stands for
Match the items in Column-A with that of Column-B:
Choose the option that matches the items of Column A with that of B correctly:
Amplification of gene of interest by using DNA polymerase may go up to:
Identify the labelled parts P, Q, R, and S in the stages of a dicot embryo shown in the diagram.
stages of a dicot embryo
Choose the option that indicates correct labelling of 'P', 'Q', 'R', and 'S' of embryo in differenct stages of its development.
The process of mineralization by microorganisms helps in the release of:
A man whose father was colour-blind marries a woman who had a colour-blind mother and normal father. What percentage of male children of this couple will be colour-blind?
If the projection of \( \mathbf{a} = \alpha \hat{i} + \hat{j} + 4 \hat{k} \) on \( \mathbf{b} = 2 \hat{i} + 6 \hat{j} + 3 \hat{k} \) is 4 units, then \( \alpha \) is:
A 1 cm straight segment of a conductor carrying 1 A current in \( x \)-direction lies symmetrically at the origin of Cartesian coordinate system. The magnetic field due to this segment at point (1m, 1m, 0) is:
Two long solenoids of radii \( r_1 \) and \( r_2 \) (\( > r_1 \)) and number of turns per unit length \( n_1 \) and \( n_2 \) respectively are co-axially wrapped one over the other. The ratio of self-inductance of inner solenoid to their mutual inductance is:
The focal length of a concave mirror in air is \( f \). When the mirror is immersed in a liquid of refractive index \( \frac{3}{5} \), its focal length will become:
A diamagnetic substance is brought, one by one, near the north pole and the south pole of a bar magnet. It is:
Atomic spectral emission lines of hydrogen atom are incident on a zinc surface. The lines which can emit photoelectrons from the surface are members of:
A coil of an AC generator, having 100 turns and area 0.1 m² each, rotates at half a rotation per second in a magnetic field of 0.02 T. The maximum emf generated in the coil is:
Which one of the following statements is correct? Electric field due to static charges is: