CBSE Class 12 Biology Exam 2025 Most Repeated Questions

Serial Number

Questions

1

What is the economic value of Spirulina?

2

Name the organism commercially used for the production of single cell protein.

3

Name the type of human cell HIV attacks at its entry into the body. Explain the events that occur in the cell which further lead to cause immunodeficiency syndrome.

4

Differentiate between the following:
(i) Perisperm and Pericarp
(ii) Syncarpous pistil and Apocarpous pistil
(iii) Plumule and Radicle

5

Explain the zygote intrafallopian transfer technique (ZIFT). How is intrauterine transfer technique (IUT) different from it?

6

(i) Write the scientific names of the two species of filarial worms causing filariasis. (ii) How do they affect the body of infected persons? (iii) How does the disease spread?

7

(i) Describe the characteristics a cloning vector must possess. (ii) Why DNA cannot pass through cell membrane? Explain. How is a bacterial cell made competent to take up recombinant DNA from the medium.

8

List the specific symptoms of pneumonia. Name the causative organism.

9

EcoRI is used to cut a segment of foreign DNA and that of vector DNA to form a recombinant DNA. Show with the help of schematic diagrams.

10

Biotechnologists refer to Agrobacterium tumefaciens as a natural genetic engineer of plants. Give a reason to support the statement.

11

Expand the name of enzyme ADA. Why is the enzyme essential in the human body? Suggest a gene therapy for its deficiency.

12

A human being suffering from Down’s syndrome shows trisomy of the 21st chromosome. Mention the cause of this chromosomal abnormality.

13

Assertion (A): A patient with ADA deficiency undergoing treatment for gene therapy requires periodic infusion of genetically engineered lymphocytes.
Reason (R): Lymphocytes are immortal.

14

Assertion (A): A cattle egret and grazing cattle in close association is a classic example of commensalism.
Reason (R): As grazing cattle move through the field; they stir up and flush out insects from the vegetation that otherwise might be difficult for egrets to find and catch.

15

Write full form of ELISA.