ISC 2025 Biotechnology Question Paper for Class 12

About this paper

This is ISC Class 12 Biotechnology Paper 1 (Theory) from the 2025 CISCE board examination, paper code 878A (printed as 1225-878A). It carries 70 marks and runs for three hours, with fifteen minutes extra for reading. All 12 questions are compulsory. Section A is Question 1, ten very short subparts totalling 14 marks, including gel electrophoresis, blue-white screening 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. Later questions include a PCR temperature graph, an explant-culture diagram, and a passage on the hybridoma work of George Kohler and Cesar Milstein. 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 a PCR graph and a hybridoma passage; internal choice in one question

Topics covered

• Gel electrophoresis
• Bacterial growth
• Blue-white screening
• Restriction enzymes
• Southern blotting
• Bioreactors and continuous culture
• DNA structure
• Lac operon
• Gene libraries and gene transfer
• Transgenic crops
• Plant and animal cell culture
• PCR and hybridoma technology

Questions from this paper

1. A bacterial strain with a doubling time of 10 minutes is cultured on L.B. agar and incubated for one hour. If 1400 cells were inoculated, how many cells are expected?
2. In DNA profiling, fragments A, B, C and D are 25 kb, 48 kb, 28 kb and 51 kb. In what order do they migrate from the cathode towards the anode?
3. Why is colchicine used during synchronisation of cells in plant cell culture?
4. A DNA fragment of 980 base pairs contains 360 guanine bases. How many purine bases does it contain?
5. Explain how Calgene produced tomatoes with a longer shelf life, and how Ingo Potrykus and Peter Beyer contributed to a rice variety of high nutritional value.
6. DNA is amplified through 12 cycles. How many copies are present at the end of the process?