CBSE Class 12 Biology Answer Key 2024, Question Paper All SET 1,2,3,4

CBSE Class 12 Biology Answer Key 2024: The Central Board of Secondary Education has conducted the CBSE Class 12th Biology exam 2024 today i.e., March 19, 2024 at various examination centers. The exam has been commenced at 10:30 am in the morning and lasted till 01:30 pm in the afternoon. As the exam is successfully conducted, students can download the complete CBSE Class 12th Biology Answer Key 2024 with a complete question paper analysis. However students must understand that the answer key may not always be accurate, so cross-checking with the official sources is very important.

CBSE Class 12 Biology Answer Key 2024

The Central Board of Secondary Education has conducted the CBSE Class 12th Biology Board Examination 2024 from 10:30 am. The Biology exam is being conducted in pen and paper mode for a total time duration of three hours i.e., from 10:30 am to 01:30 pm, and an extra 15 minutes will be given for reading the Biology question paper. The students appearing for the examination are informed that the Question paper will comprise 5 different sections that are: Sections A, B, C, D, and E.

Class 12 Biology Answer Key 2024

The CBSE Class 12th Biology Question paper will consist of five sections with a total of 33 questions. Where Section A will have 16 questions of one mark each. Section B will comprise Five questions carrying two marks each. Section C will be a set of Seven questions of three marks each. Whereas Section D consists of Two case-based questions of four marks each and Section E will have Three questions carrying five marks each.

CBSE Class 12 Biology Answer Key 2024
Exam Conducting Body	Central Board of Secondary Education (CBSE)
Name of Examination	CBSE Class 12th Board Examination 2024
Category	Answer Key
Status	To be Released
CBSE Class 12th Biology exam date 2024	March 19, 2024
CBSE Class 12th Biology Answer Key Release Date	March 2024
Mode of Answer Key Availability	Online Mode
Class 12th Biology Total Marks (Theory Exam)	70 Marks
Negative Marking	No Marks will be deducted for any wrong attempt
Official Website	https://www.cbse.nic.in/

As the exam has been conducted, our team will keep on updating the answer key for all the questions asked. Please keep refreshing the page.

CBSE Class 12 Biology Paper Analysis 2024

Most of the students who appeared for the CBSE Class 12 Biology Exam today i.e., March 19, 2024 found the paper a bit tricky but well-structured. Students have mentioned that all questions were based on the syllabus and followed the same format as the latest CBSE class 12th Biology sample paper 2024.

1. The overall difficulty level of the question paper was moderate.
2. Students have also said that the question paper was slightly lengthy.
3. Students said that the biology exam question paper was moderate with MCQs being easier than the rest of the paper.
4. A similar trend is being expected from the CBSE Class 12 Biology Question Paper 2024.
5. Students have said that the question paper was moderate.
6. The questions were direct and to the point.
7. Section A, comprising MCQs and assertion-reason-based questions, was the highest-scoring and easiest portion.
8. Section D, especially Section C involving short answer and case-based questions, posed the most difficulty, necessitating creative thinking.

CBSE Class 12 Biology Answer Key 2024 All SET

Section A

( Each Question 1 Mark)

1. An angiosperm embryo sac is located within the:

(A) Placenta
(B) Megasporangium
(C) Nucellus
(D) Ovary

2. Match the items in Column I with those in Column II and select right option.

(A) 1-ii, 2-iv, 3-i, 4-iii
(B) 1-iii, 2-i, 3-iv, 4-ii
(C) 1-iii, 2-iv, 3-i, 4-ii
(D) 1-ii, 2-i, 3-iv, 4-iii

3. In Humans, the secondary oocyte completes meiotic division when:

(A) it gets implanted in the uterine endometrium
(B) it is released from the matured Graafian follicle
(C) it is penetrated by the sperm cell
(D) acrosomal enzymes break down the zona pellucid

4. Which one of the following statements is not true?

(A) Flippers of whales and dolphins are homologous organs
(B) Homologous organs have similar anatomical structure, but perform different functions
(C) Homology indicates common ancestry
(D) Homologous structures are a result of convergent evolution

5. A Population is in genetic equilibrium/Hardy-Weinberg equilibrium for a gene with 3 alleles (dominant allele is ‘A’ and recessive allel ‘a’). If the frequency of allele ‘A’ is 0.6, then the frequency of genotype ‘Aa’ is:

(A) 0.21
(B) 0.42
(C) 0.48
(D) 0.32

6. In the double helical structure of DNA molecule, the strands are:

(A) identical and complementary
(B) identical and non-complementary
(C) anti-parallel and complementary
(D) anti-parallel and non-complementary

7. In a ‘transcription unit’, the ‘terminator’ is located towards the:

(A) 3′ end of the template strand
(B) 5′ end of the template strand
(C) 5′ end of the coding strand
(D) 3′ end of the coding strand

8. A woman with normal vision has a colour blind father. She marries a man with normal vision. The percentage chance of their progeny being colour blind is:

(A) 25%
(C) 75%
(B) 50%
(D) 100%

9. The vector for dengue fever is:

(A) Female Aedes mosquito
(B) Female Anopheles mosquito
(C) Male Aedes mosquito
(D) Female Culex mosquito

11.Which one of the following is not a feature of plasmids?
(A) Circular
(B) Self-replicating
(C) Single stranded
(D) Extra-chromosomal

12. The pyramid of biomass in sea is generally inverted because in sea:

(A) Biomass of fishes exceeds that of phytoplankton.
(B) Number of phytoplanktons is more.
C) Number of phytoplanktons is less.
(D)) Large fishes feed on small fishes

CBSE Class 12th Biology Set 57/5/1

SECTION-A

Question Nos. 1 to 16 are Multiple Choice type Questions, carrying 1 mark each. 16 x 1 = 16

1. A single gene that controls the expression of more than one trait is said to show

(A) Multiple allelism

(B) Polygenic inheritance

(C) Incomplete dominance

(D) Pleiotropism

2. A person with trisomy of 21st chromosome shows

(i) Furrowed tongue

(ii) Characteristic palm crease

(iii) Rudimentary ovaries

(iv) Gynaecomastia

Select the correct option, from the choices given below:

(A) (ii) and (iv)

(B) (i), (ii) and (iv)

(C) (ii) and (iii)

(D) (i) and (ii)

3. Observe the schematic representation of assisted reproductive technology given below :

Identify the most appropriate technique depicted in the above diagram.

(A) IUT

(B) IUI

(C) ICSI

(D) ZIFT

4. Interferons are proteins secreted by

(A) RBC

(B) WBC

(C) Bacteria infected cell

(D) Virus infected cell

5. During biological treatment of sewage, the masses of bacteria held together by fungal filaments to form mesh like structures are called

(A) primary sludge

(B) flocs

(C) activated sludge

(D) anaerobic sludge

6. Which one of the following statements is correct in the context of observing DNA separation by agarose gel electrophoresis?

(A) DNA can be seen in visible light.

(B) DNA can be seen without staining in visible light.

(C) Ethidium bromide stained DNA can be seen in visible light

(D) Ethidium bromide stained DNA can be seen under UV light.

7. A phenomenon where a male insect mistakenly identified the patterns of a orchid flower as the female insect partner, and tries to copulate and thereby pollinates the flower is said to be :

(A) Pseudocopulation

(B) Pseudopollination

(C) Pseudoparthenocarpy

(D) Pseudofertilisation

8. Identify the correct labellings in the figure of a fertilised embryo sac of an angiosperm given below :

(A) A – zygote, B – degenerating synergids, C – degenerating antipodals, D-PEN

(B) A – degenerating synergids, B – zygote, C – PEN, D – degenerating antipodals

(C) A – degenerating antipodals, B – PEN, C degenerating synergids, D-zygote

(D) A degenerating synergids, B – zygote, C-degenerating antipodals, D-PEN

9. Study the pedigree chart of a family showing the inheritance pattern of a certain disorder. Select the option that correctly identifies the nature of the trait depicted in the pedigree chart.

(A) Dominant X – linked

(B) Recessive X – linked

(C) Autosomal dominant

(D) Autosomal recessive

10. Match the following genes of the lac operon listed in column ‘A’ with their respective products listed in column ‘B’:

Select the correct option:

Options:

(A) (i) (iii) (ii) (iv)

(B) (iii) (i) (ii) (iv)

(C) (iii) (i) (iv) (ii)

(D) (iii) (iv) (i) (ii)

11. If both the parents are carriers for thalassaemia, the chances of an afflicted child to be born to them is:

(A) 25%

(B) 50%

(C) 75%

(D) 100%

12. If the sequence of nitrogen bases of the coding strand in a transcription unit is 5′-ATGAATG-3′, the sequence of bases in its RNA transcript would be

(A) 5′-AUGAAUG – 3′

(B) 5′-UACUUAC – 3′

(C) 5′-CAUUCAU – 3′

(D) 5′-GUAAGUA – 3′

Question number 13 to 16 consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:

(A) Both (A) and (R) are true and (R) is the correct explanation of (A).

(B) Both (A) and (R) are true, but (R) is not the correct explanation of (A).

(C) (A) is true, but (R) is false.

(D) (A) is false, but (R) is true.

13. Assertion (A): AIDS is a syndrome caused by HIV.

Reason (R): HIV is a virus that damages the immune system with DNA as its genetic material.

14. Assertion (A): In molecular diagnosis, single stranded DNA or RNA tagged with radioactive molecule is called a probe.

Reason (R): A probe always searches and hybridises with its A complementary DNA in a clone of cells.

15. Assertion (A): In birds the sex of the offspring is determined by males.

Reason (R) : Males are homogametic while females are heterogametic.

16. Assertion (A): Communities that comprise of more species tend to be more stable.

Reason (R) : A higher number of species results in less year to year variation in total biomass.

SECTION-B

17. (a) “Farmers prefer apomictic seeds to hybrid seeds.” Justify giving two reasons.

OR

(b) Mention one advantage and one disadvantage of amniocentesis.

18. 5′-G^↓ AATTC-3

3′-CTTAA_↑G-5′

(a) Name the restriction enzyme that recognises the given specific sequence of bases. What are such sequence of bases referred to as ?

(b) What are the arrows in the given figure indicating? Write the result obtained thereafter.

19. Observe the population growth curve and answer the questions given below:

(a) State the conditions under which growth curve ‘A’ and growth curve ‘B’ plotted in the graph are possible.

(b) Mention what does ‘K’ in the graph represent.

20. Explain how are plants benefitted by their association with “Glomus species”.

21. If the base adenine constitutes 31% of an isolated DNA fragment, then write what will be the expected percentage of the base cytosine in it. Explain how did you arrive at the answer given.

SECTION – C

22. Identify a, b, c, d, e and f in the table given below :

23. (a) Tropical regions harbour more species than the temperate regions. How have biologists tried to explain this in their own ways? Explain.

OR

(b) (i) What does an ecological pyramid represent?

(ii) The Ecological pyramids may have an ‘upright’ or an ‘inverted’ shape. Justify with the help of suitable examples.

24. (a) What are transgenic animals ?

(b) Name the transgenic animal having the largest number amongst all the existing transgenic animals.

(c) State any 3 reasons for which these types of animals are being produced.

25. If the cells in the leaves of a maize plant contain 10 chromosomes each, write the number of chromosomes in its endosperm and zygote. Name and explain the process by which an endosperm and a zygote are formed in maize.

26. (a) Why does DNA replication occur within a replication fork and not in its entire length simultaneously?

(b) “DNA replication is continuous and discontinuous on the two strands within the replication fork.” Explain with the help of a schematic representation.

27. Explain the processing of heterogeneous nuclear RNA (hnRNA) into a fully functional mRNA in eukaryotes. Where does this processing occur in the cell?

28. The world is facing accelerated rates of species extinction largely due to human activities. Explain any three human activities responsible for accelerated rates of species extinction.

SECTION-D

Q. No. 29 and 30 are case based questions. Each question has 3 sub- questions with internal choice in one sub-question.

29. In a human female, the reproductive phase starts on the onset of puberty and ceases around middle age of the female. Study the graph given below regarding menstrual cycle and answer the questions that follow :

(a) Name the hormones and their source organ, which are responsible for menstrual cycle at puberty.

(b) For successful pregnancy, at what phase of the menstrual cycle an early embryo (upto 3 blastomeres) should be Implanted in the Uterus (IUT) of a human female who has opted for Assisted Reproductive Technology (ART)? Support your answer with a reason.

(c) Name the hormone and its source organ responsible for the events occurring during proliferative phase of menstrual cycle. Explain the event.

OR

(c) In a normal human female, why does menstruation only occurs if the released ovum is not fertilised? Explain.

30. Read the following passage and answer the questions that follow :

“Mosquitoes are drastically affecting the human health in almost all the developing tropical countries. Different species of mosquitoes cause very fatal diseases so much so that many humans loose their life and if they survive, are unable to put in productive hours to sustain their life. With the result the health index of the country goes down.”

(a) Name the form in which Plasmodium gains entry into

(i) human body

(ii) the female Anopheles body.

(b) Why do the symptoms of malaria not appear in a person immediately after being bitten by an infected female Anopheles? Give one reason. Explain when and how do the symptoms of the disease would appear.

OR

(a) Explain the events which occur within a female Anopheles mosquito after it has sucked blood from a malaria patient.

(b) Name a species of mosquito other than female Anopheles and the disease, for which it carries the pathogen.

SECTION-E

31. (a) Draw a schematic diagram of the cloning vector pBR 322 and label

(1) Bam HI site

(2) gene for ampicillin resistance

(3) ‘ori’

(4) ‘rop’ gene.

(ii) State the role of ‘rop’ gene.

(iii) A cloning vector does not have a selectable marker. How will it affect the process of cloning?
(iv) Why is insertional inactivation preferred over the use of selectable markers in cloning vectors?

OR

(b) (i) Name the nematode (scientific name) that infects the roots of tobacco plant and reduces its yield.

(ii) Name the vector that is used to introduce nematode-specific genes into the host plant (tobacco).

(iii) How do sense and anti-sense RNAs function?

(iv) Why could parasite not survive in a transgenic tobacco plant?

CBSE Class 12 Biology Exam Analysis 2024 Live

All the students who appeared in the Class 12 Biology Exam, can check the 100% accurate Class 12 Biology Exam Analysis 2024 by the Adda247 team.

Class 12 Biology Question Paper 2024 PDF Download

On March 19, 2024, the Central Board of Secondary Education conducted the Class 12th Biology Exam 2024. The CBSE Board Question Papers are valuable resources as after the successful conduction of the exam, these question papers help the students to evaluate their performance in the exams. They also give an overview of papers to students preparing to appear in the class 12th exams next year of the types. In order to download the CBSE Class 12th Biology Question Paper 2024 PDF, the direct link will be updated below:

Class 12 Biology Answer Key 2024 PDF Download

Students who appeared for the CBSE Class 12th Biology exam can get an overview of the exam score and the overall performance in the Class 12 Biology examination. As the exam is successfully conducted, students who are looking for the Class 12th Biology Answer Key 2024 are advised to check the link mentioned below. Our subject expert’s faculty will release the specially designed answer key for the questions that will be asked in the CBSE Class 12th Biology Exam. The CBSE Class 12 Biology Answer Key 2024 PDF can easily be downloaded from the direct link that has been shared here.

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