CBSE Class 12 Biology - 5 Marks Important Questions

Some of the important 5 marks biology questions for CBSE class 12 board exam are given below. The questions are in accordance with the latest CBSE curriculum and are from the various chapters in the CBSE syllabus. By solving these CBSE class 12 biology important questions, students can analyze their preparation and get acquainted with a wide range of questions.

Important Points to Note:

  1. In 5 marks questions, students need to explain all the relevant points related to the question.
  2. 3 questions are included in the 5 marks section which also includes internal choices.
  3. It is suggested to write 15-20 lines and draw a labeled diagram.
  4. Step markings are given and so, it is important to write proper facts and label the diagrams correctly.

Apart from these questions, students are also suggested to visit important questions for Class 12 biology and check various chapter-wise sample questions from biology.

Important 5 marks Biology Questions For Class 12 Board Exam

Question 1:

(a) Explain why many embryos, instead of one are observed when the seed of an orange is squeezed.

(b) Comment on the genetical similarity of these embryos.

Question 2:

(a) Draw a sectional view of a seminiferous tubule of human. Label sertoli cell, spermatogonia and leydig cell on it and write their functions.

(b) Explain the role of pituitary and sex hormones in the process of spermatogenesis.

Question 3:

Explain the structure of t-RNA with the help of a diagram. Describe its role in the process of translation.

Question 4:

Explain the application of rDNA technology to produce insulin.

Question 5:

(a) Describe the different steps in one complete cycle of PCR.

(b) State the purpose of such an amplified DNA sequence.

Question 6:

(a) Describe in sequence the process of microsporogenesis in angiosperms.

(b) Draw a labelled diagram of a two celled final structure formed.

Question 7:

(a) What is Central dogma? Who proposed it?

(b) Describe Meselson and Stahl’s experiment to prove that the DNA replication is semi-conservative.

Question 8:

A pea plant producing yellow coloured and round seeds is given with unknown genotypes. Explain how you would find the correct genotypes of the plants with respect to the two traits mentioned. Work out the cross and name it.

Question 9:

(a) Describe the different steps in one complete cycle of PCR.

(b) State the purpose of such an amplified DNA sequence.

Question 10:

(a) Compare, giving reasons, the J-shaped and S-shaped models of population growth of a species.

(b) Explain ‘‘fitness of a species’’ as mentioned by Darwin.

Question 11:

(a) Explain Polygenic inheritance and Multiple allelism with the help of suitable examples.

(b) ‘‘Phenylketonuria is a good example that explains Pleiotropy.’’ Justify.

Question 12:

(a) Explain the following phases in the menstrual cycle of a human female :

  • (i) Menstrual phase
  • (ii) Follicular phase
  • (iii) Luteal phase

(b) A proper understanding of menstrual cycle can help immensely in family planning. Do you agree with the statement? Provide reasons for your answer.

Question 13:

(a) What is an operon?

(b) Explain how a polycistronic structural gene is regulated by a common promoter and a combination of regulatory genes in a

Question 14:

(a) What is an ecological pyramid? Compare the pyramids of energy, biomass and numbers.

(b) Write any two limitations of ecological pyramids.

Question 15:

(a) State the objective of animal breeding.

(b) List the importance and limitations of inbreeding. How can the limitations be overcome?

(c) Give an example of a new breed each of cattle and poultry.

Question 16:

Describe the role of pituitary and ovarian hormones during the menstrual cycle in a human female.

Question 17:

(a) Why are thalassemia and haemophilia categorized as Mendelian disorders? Write the symptoms of these diseases. Explain their pattern of inheritance in humans.

(b) Write the genotypes of the normal parents producing a haemophilic son.

Question 18:

(a) List the different attributes that a population has and not an individual organism.

(b) What is population density? Explain any three different ways the population density can be
measured, with the help of an example each.

Question 19:

How do m-RNA, t-RNA and ribosomes help in the process of translation?

Question 20:

(a) When a seed of an orange is squeezed, many embryos, instead of one are observed. Explain how it is possible.

(b) Are these embryos genetically similar or different? Comment.

Question 21:

(a) Explain the different ways apomictic seeds can develop. Give an example of each.

(b) Mention one advantage of apomictic seeds to farmers.

(c) Draw a labelled mature stage of a dicotyledonous embryo.

Question 22:

“It is often said that the pyramid of energy is always upright. On the other hand, the pyramid of biomass can be both upright and inverted.” Explain with the help if examples and sketches.

Question 23:

(a) Describe the structure and function of a t-RNA molecule. Why is it referred to as an adapter molecule?

(b) Explain the process of splicing of hn-RNA in a eukaryotic cell.

Question 24:

(a) Describe the various steps of Griffith’s experiment that led to the conclusion of the ‘Transforming Principle’.

(b) How did the chemical nature of the ‘Transforming Principle’ get established?

Question 25:

Write the different components of a lac-operon in E. coli. Explain its expression while in an ‘open’ state.

These were a few important 5 marks questions for CBSE class 12 biology exam. All these questions are from the syllabus topics and similar questions are likely to be included in the board exam. Students can also check CBSE question papers for class 12 biology and get more important sample questions from biology.

Stay tuned with BYJU’S to get more practice questions, study materials and preparation tips for the class 12 board exams.



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  1. plz appoint large amt of questions for board exam 2021 for pcb like imp 5 marks or dia and graph baesd