ISC 2025 Biotechnology Improvement Examination Question Paper for Class 12

About this paper

This is ISC Class 12 Biotechnology Paper 1 (Theory) from CISCE's 2025 Improvement Examination, paper code 878A (printed as 1225-878A-IE). It carries 70 marks and runs for three hours, with fifteen minutes extra for reading. All 12 questions are compulsory. Section A is 14 marks of very short answers, from cDNA-library enzymes to two assertion–reason items. Section B has seven four-mark questions and Section C four seven-mark questions, with an internal choice in two questions of Section B and one of Section C. The paper includes the Hershey–Chase experiment, cryopreservation at −196°C, a colorimeter diagram, and a passage on using Agrobacterium tumefaciens to modify cotton and rice. This copy has the questions only.

Exam

ISC Class 12

Subject

Biotechnology

Year

2025

Paper code

878A

Maximum marks

70

Time allowed

3 hours + 15 min reading

Questions

12

Pages

8

Answers included

No, questions only

Paper pattern

• Section A

  14 marks

  Question 1: ten very short-answer subparts totalling 14 marks, including two assertion–reason items

• Section B

  28 marks

  Questions 2–8, four marks each; internal choice in two questions

• Section C

  28 marks

  Questions 9–12, seven marks each, including an Agrobacterium passage; internal choice in one question

Topics covered

• cDNA library
• DNA replication and transcription
• Gel electrophoresis
• Plant tissue culture
• Single-cell protein
• Gene gun and electroporation
• Recombinant insulin
• Hershey and Chase experiment
• Cryopreservation
• Human Genome Project
• Inducible operon
• Agrobacterium-mediated gene transfer

Questions from this paper

1. Which enzyme removes the hairpin loop formed while a cDNA library is being prepared, so that the DNA becomes double-stranded?
2. A lagging strand has 188 Okazaki fragments, and one phosphodiester bond joins two fragments. How many such bonds does DNA ligase form?
3. Why is a haploid plantlet treated with colchicine in cell culture?
4. Which elements did Hershey and Chase radiolabel, and where is each element found in the bacteriophage?
5. Nalini preserved seeds of a rare rice variety at −196°C. Name the technique, and state how that temperature was obtained.
6. Why is Agrobacterium tumefaciens called a natural genetic engineer, and why did Steve succeed in transforming cotton but not rice?