ISC 2026 Biotechnology Question Paper for Class 12

About this paper

This is ISC Class 12 Biotechnology Paper 1 (Theory) from the 2026 CISCE board examination, paper code 878A (printed as 1226-878A). 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, including the genetic code, synthetic seeds and 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. Among the longer items are Agrobacterium gene transfer, automated DNA sequencing, protoplast isolation, and a comparison of chemostat and turbidostat cultures of Streptomyces and E. coli. This copy has the questions only.

Exam

ISC Class 12

Subject

Biotechnology

Year

2026

Paper code

878A

Maximum marks

70

Time allowed

3 hours + 15 min reading

Questions

12

Pages

11

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 sequencing and continuous-culture passages; internal choice in one question

Topics covered

• DNA isolation
• Finite cell lines
• Genetic code
• Synthetic seeds
• Stem cells
• DNA replication
• Blotting techniques
• Cloning vectors and recombinant vaccines
• Gene libraries
• Agrobacterium-mediated gene transfer
• DNA sequencing
• Chemostat and turbidostat

Questions from this paper

1. Why is EDTA added to the lysis buffer used while isolating DNA from a bacterial cell?
2. A DNA fragment 6.8 nm long contains 20% adenine. How many hydrogen bonds are present in it?
3. Why is a co-repressor required, along with the repressor, to switch off a repressible operon?
4. Why are expressed sequence tags obtained from mRNA and not from genomic DNA?
5. The codon GAU (aspartate) in subtilisin is changed to GUU (valine) using M13 bacteriophage and a Nobel laureate's method. Explain the technique.
6. Meera limits glucose while growing Streptomyces for antibiotics, and Benjamin monitors the cell density of an E. coli culture. Identify the open continuous culture system used by each.