List of top Questions asked in CBSE CLASS XII- 2026

What is meant by translation in protein synthesis?
Explain charging of tRNA (aminoacylation of tRNA) and mention its importance in the process of translation.
GEAC is a regulatory body under the Ministry of Environment, Forest and Climate Change in India.
Write the full form of GEAC.
Mention two of its important functions related to biotechnology.
After performing gel electrophoresis, a student observes that DNA fragments are not visible.
Suggest a reason for this and explain how fragments can be made visible.
Also explain how a specific DNA fragment can be collected from the gel for further use.
What did Henking observe in his experiments on insects that led to the discovery of sex chromosome? How did his observation contribute to our understanding of sex determination?
Given below is the schematic representation of the process of electrophoresis. Identify the alphabets representing the:
Anode end, and
Lightest/Smallest DNA in matrix.
What is Agarose gel and why is it used in this process?
Explain the different ways by which apomictic seeds can be developed.
Mention one advantage of apomictic seeds for farmers.
Mention any two characteristics of Neanderthal man that lived near East and Central Asia.
A person complains of persistent itching in the groin region and scalp. The person also shows dry and scaly lesions on skin, nails, etc.
Identify the disease.
Name its two causative agents.
(iii) Mention its mode of transmission.
A girl develops sneezing, watery eyes and difficulty in breathing every time she visits a flower garden.
Identify the condition.
Name the immune component responsible for this condition.
(iii) Name the chemical released.
(iv) State one medicine used to treat such a condition.
The allele for brown eyes is dominant over blue eyes . In a population, 36% of individuals have blue eyes. Assuming Hardy-Weinberg equilibrium, calculate:
Frequency of allele B
Percentage of heterozygous individuals
(iii) Percentage of individuals that are homozygous dominant
(Working to be shown)
Identify the following hominids with respect to human evolution:
Brain capacity 900 cc, probably ate meat.
First human-like with brain capacity 650 - 800 cc.
Assertion (A): Repetitive sequences are stretches of DNA sequences that are thought to have no direct coding functions.
Reason (R): They shed light on chromosome structure, dynamics and evolution.
The smallest part of DNA molecule that can be changed by point mutation is :
Select the correct option for the pair of plants pollinated by water.
Assertion (A): DNA cannot pass through cell membrane of a bacterial cell.
Reason (R): DNA is a hydrophilic molecule.
Assertion (A): Activated sludge contains large population of bacteria.
Reason (R): These bacteria help in anaerobic digestion of human waste in biogas plant.
Some statements regarding drugs and alcohol are given below :
(i) Adolescents are more vulnerable to peer pressure.
(ii) Drug addiction leads to increased tolerance level of the receptors present in our body.
(iii) Alcohol affects the central nervous system.
(iv) Excessive use of drugs helps to increase energy.
(v) Anabolic steroids decrease aggressiveness.
Choose the option with correct statement(s).
Assertion (A): Ecosystems require a constant supply of energy to synthesize the molecules they require.
Reason (R): This is to counteract the universal tendency towards increasing disorderliness as per Second Law of Thermodynamics.
Appearance of antibiotic-resistant bacteria is an example of evolution due to:
Identify the statements that correctly describe Darwin's Theory of Evolution.
(i) Overproduction of organisms leads to competition.
(ii) Variation is inherited and causes evolution.
(iii) Acquired characters are inherited.
(iv) Survival depends on favourable traits.
(v) New species arise due to accumulation of favourable variations.
Choose the correct option.
Four different transcription units are shown below. Choose the option with the correct image.
Which of the following is not a symptom of Ascariasis ?
Every trophic level has a certain mass of living material at a particular time. What is it called?
Foetal ejection reflex in human female triggers the release of which hormone?