List of top Questions asked in CBSE CLASS XII

Compare and contrast convergent and divergent evolution.

(a) Indiscriminate human activities such as alien species invasion, fragmentation and habitat loss have accelerated the loss of biodiversity. Justify by taking one example for each.
(b) State the importance of the following:
(i) IUCN Red data list
(ii) Hot spots in conservation of biodiversity

Describe in brief any two techniques that can be utilised to transfer recombinant DNA into the host cell directly without using any vector.

Shyam and Radha are expecting their first child with Radha being in her second month of pregnancy with no complications. Shyam’s family has a history of cystic fibrosis while Radha’s family has a history of Down’s syndrome, leading to a concern that the baby may have one of these conditions.
(a) Suggest and explain a way of testing if their baby is at risk for any genetic disorders.
(b) In case of presence of one or both of the abnormalities and posing a risk to the mother’s health, mention one possible option for them to consider. Is that option safe for Radha at the current gestational age? Justify.
(c) Under what conditions is the process mentioned in (b) illegal?

Study a part of life cycle of Plasmodium given below:

Answer the following questions:
(a) Name the infective stage of Plasmodium that is stored in the female Anopheles mosquito.
(b) Where does fertilization and development of parasite take place?
(c) Identify labels P and Q in the given diagram.
(d) Asexual and sexual phase of the life cycle of the Plasmodium takes place in two different hosts. Write their names.

A patient with ADA deficiency requires periodic infusion of genetically engineered lymphocytes. Explain why such periodic infusion is required and also suggest a permanent cure for such ADA deficiency.

Study the pedigree chart given below, showing the inheritance pattern of blood group in a family:

Answer the following questions:
(a) Give the possible genotypes of individual 1 and 2.
(b) Which antigen or antigens will be present on the plasma membranes of the R.B.Cs of individuals ‘5’ and ‘8’?

Study the diagram given below and answer the questions that follows:

(a) Identify the structure shown in the above figure.
(b) Identify the labels P and Q.
(c) Write the nature of histone proteins.
(d) Distinguish between Euchromatin and Heterochromatin.

(A) Analyse the following ecosystems and discuss, which will be more productive in terms of primary productivity:
A young forest, a natural old forest, a shallow polluted lake.

(A) How are morphine and heroin related? Mention their effect on the human body.

Study the cross given below:

Identify the abnormalities ‘1’ and ‘2’ in the offsprings of a cross done between a couple and distinguish between them.