HBSE Class 12 Biology Pre-Board Question Paper 2024 Answer Key

Haryana Board (HBSE) Class 12 Biology Pre Board Question Paper 2024 Answer Key. Haryana Board Class 12th Pre Board Question Paper PDF Download 2024. Haryana Board Class 12th Pre Board Question Paper Biology 2024. HBSE Class 12th Biology Pre Board Question Paper Solution 2024. HBSE Biology Pre Board Question Paper 2024 Class 12.

HBSE Class 12 Biology Pre-Board Question Paper 2024 Answer Key

Section – A (1 Mark)

1. Relaxin hormone is secreted by :
(a) Rete testis
(b) Leydig cells
(c) Ovary
(d) Fallopian tube
Answer – (c) Ovary

2. Which of the following is not a wall layer of the microsprangium?
(a) Epidermis
(b) Endothecium
(c) Endothelium
(d) Tapetum
Answer – (b) Endothecium

3. How many male gametes are formed in a single male gametophyte?
(a) 2
(b) 4
(c) 6
(d) 8
Answer – (a) 2

4. Convergent evolution is shown by :
(a) Eye of octopus and mammals
(b) Sweet potato and potato
(c) Flippers of penguins and dolphins
(d) All of the above
Answer – (d) All of the above

5. In a transcription unit, the promoter is located towards :
(a) 5’end of the stuctural gene
(b) 3’end of the structural gene
(c) 5’end of the template strand
(d) 3’end of the codind strand
Answer – (a) 5’end of the structural gene

6. In eukaryotes, RNA II facilitates transcription of :
(a) rRNA
(b) mRNA
(c) tRNA
(d) hnRNA
Answer – (b) mRNA

7. Which of the following is a recessive trait for a character choosen by Mendel in garden pea?
(a) Violet flower color
(b) Yellow pod colour
(c) Axial flower position
(d) Tall stem height
Answer – (b) Yellow pod colour

8. Which of the following is a viral disease?
(a) Diphtheria
(b) Filariasis
(c) Leprosy
(d) Influenza
Answer – (d) Influenza

9. Which of these processes does not give off CO2?
(a) Lactate fermentation
(b) Aerobic respiration
(c) Alcoholic fermentation
(d) None of the above
Answer – (a) Lactate fermentation

10. Agarose extracted from sea weeds finds use in ……………
(a) Spectrophotometry
(b) Gel electrophoresis
(c) PCR
(d) Tissue culture
Answer – (b) Gel electrophoresis

11. The first ever human hormone produced by recombinant DNA technology is ……………
(a) Progestrone
(b) Insulin
(c) Estrogen
(d) Thyroxin
Answer – (b) Insulin

12. Darwinian fitness is represented by :
(a) Low r value
(b) High r value
(c) High K value
(d) Low K value
Answer – (b) High r value

13. The upright pyramid of numbers is absent in :
(a) Forest
(b) Grassland
(c) Pond
(d) Lake
Answer – (a) Forest

14. Which of the following is not a method of ex-situ conservation?
(a) Cryopreservation
(b) In vitro fertilization
(c) National parks
(d) Micropropagation
Answer – (c) National parks

15. Assertion (A) : Cross of F1 individual with recessive homozygous parent is test cross.
Reason (R) : No recessive individual are obtained in the monohybrid test cross progeny.
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both assertion and Reason are true but Reason is not the correct explanation of Assertion.
(c) If Assertion is true but Reason is false.
(d) If both Assertion and Reason are false.
Answer – (c) If Assertion is true but Reason is false.

16. Assertion (A) : Histones are basic in nature.
Reason (R) : Histones are rich in the amino acids lysine and arginine.
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both assertion and Reason are true but Reason is not the correct explanation of Assertion.
(c) If Assertion is true but Reason is false.
(d) If both Assertion and Reason are false.
Answer – (a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.

17. Assertion (A) : Living organisms are regarded as open systems.
Reason (R) : Energy of Iiving organisms can be lost or gained from external environment.
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both assertion and Reason are true but Reason is not the correct explanation of Assertion.
(c) If Assertion is true but Reason is false.
(d) If both Assertion and Reason are false.
Answer – (a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.

18. Assertion (A) : Seminiferous tubules are lined by male germ cells and sertoli cells.
Reason (R) : Seminiferous tubule is structural and functional unit of testes.
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both assertion and Reason are true but Reason is not the correct explanation of Assertion.
(c) If Assertion is true but Reason is false.
(d) If both Assertion and Reason are false.
Answer – (b) If both assertion and Reason are true but Reason is not the correct explanation of Assertion.

Section – B (2 Marks)

19. Give a brief account of male accessory glands.
Answer – The glands which are not involved directly in the production of male gametes or sperm cells but whose secretions help in the process of reproduction are called as accessory glands. The accessory glands of the male reproductive system are the seminal vesicles, prostate gland, and the bulbourethral glands. These glands secrete fluids that enter the urethra.

20. What is a role of Single cell protein in human diet?
Answer – Single cell protein (SCP) refers to edible protein extracted from microorganisms such as bacteria, algae, fungi, and yeast. SCP plays a significant role in enhancing protein intake, improving nutritional quality, promoting sustainable food systems, and diversifying dietary options in the human diet.

21. What is apomixis and what is its importance?
Answer – Apomixis is the mechanism of seed production without involving the process of meiosis and syngamy. It plays an important role in hybrid seed production. The method of producing hybrid seeds by cultivation is very expensive for farmers. Also, by sowing hybrid seeds, it is difficult to maintain hybrid characters as characters segregate during meiosis. Apomixis prevents the loss of specific characters in the hybrid. Also, it is a cost-effective method for producing seeds.

22. Which Alkaloid is found in tobacco? What is its effect on human body?
Answer – Tabacco contains an alkaloid called nicotine. Nicotine is a stimulant that affects the central nervous system by increasing heart rate, blood pressure, and adrenaline levels. It is highly addictive and can lead to dependence and withdrawal symptoms when not consumed regularly. In addition to its addictive properties, nicotine is also known to have negative effects on the cardiovascular system and can contribute to the development of certain diseases such as heart disease and cancer.

23. What is the theory of spontaneous generation? Name the scientist who dismissed it?
Answer – Louis Pasteur is credited with conclusively disproving the theory of spontaneous generation with his famous swan-neck flask experiment. He subsequently proposed that “life only comes from life.”

24. How STDs can be prevented?
Answer – Sexually transmitted diseases (STDs) get transferred from one individual to the other through sexual contact.
STDs can be prevented by : The use of contraceptives, such as condoms, etc. while intercourse, can prevent the transfer of these diseases. Sex with unknown or multiple partners should be avoided as they may have such diseases. Regular medical checkup to ensure good health is necessary.

25. What is RED LIST?
Answer – The RED LIST, formally known as the IUCN Red List of Threatened Species, is a comprehensive inventory that assesses the global conservation status of plant and animal species. Created and maintained by the International Union for Conservation of Nature (IUCN), the Red List categorizes species based on their risk of extinction and aims to raise awareness and guide conservation actions. The RED LIST serves as a critical indicator of the health of the world’s biodiversity and is widely used by governments, environmental organizations, and researchers to inform conservation planning, policy making, and resource allocation.

Section – C (3 Marks)

26. What is CRY gene?
Answer – Bacillus thuringiensis is a soil dwelling bacterium which is commonly used as a biopesticide and contains a toxin called cry toxin. Scientists have introduced this toxin producing genes into cotton and have raised genetically engineered insect resistant cotton plants.

27. Define PCR and for what purpose it is used in diagnosis?
Answer – Polymerase Chain Reaction (PCR) is a reaction carried in vitro to amplify the DNA or gene of interest and create its multiple copies. It involves three steps – denaturation, annealing and extension. PCR’s versatility, sensitivity, and specificity make it invaluable for diagnosing infectious diseases, genetic disorders, cancers, and more. It allows for rapid, accurate detection and monitoring, significantly improving patient care and public health outcomes.

28. Differentiate between active and passive immunity.
Answer –

Active Immunity Passive Immunity
1. Immediate relief from ailment is not there. 1. Immediate relief from ailment.
2. Active role of sufferer in production of immunity. 2. Role of sufferer is not active.
3. Antibodies are produced on exposure to antigen. 3. Antibodies are injected.
4. Mother’s milk does not provide active immunity. 4. Mother’s milk provides passive immunity.

 

29. Draw a labelled diagram of a section through ovary.
Answer –

30. Microbes can be used to decrease the use of chemical fertilizers and pesticides. Explain how this can be accomplished?
Answer – The use of chemical fertilizers and pesticides can be reduced by the use of biofertilizers and biological pest control methods. Biofertilizers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilizers are bacteria, fungi and cyanobacteria. Many bacteria and cyanobacteria fix the atomospheric nitrogen into organic forms, thus enriching the nitrogen content of the soil. In paddy fields, cyanobacteria serve as an important biofertilizer. Similarly, some microbes (fungi, bacteria and viruses) can be used to control a number of crop pests.

Section – D (Case Study : 4 Marks)

31. In prokaryotes, DNA is circular and present in the cytoplasm but in eukaryotes, DNA is linear and mainly confined to the nucleus. DNA is a long polymer of nucleotides. In 1953, the first correct double helical structure of DNA was worked out by Watson and Crick. It is composed of three components, i.e. A phosphate group, a deoxyribose sugar and a nitrogenous base. Different forms of DNA are B-DNA, A-DNA, Z-DMA, C-DNA.
Questions :
(a) Name the linkage present between the nitrogen base and pentose sugar in DNA. (1 Mark)
Answer – Glycosidic bond

(b) Do eukaryotes also having circuler DNA? If yes, then specify where? (2 Marks)
Answer – Yes, eukaryotes also have circular DNA. It is found in Mitochondria and Chloroplast.

(c) Human possess which form of DNA ………….. (1 Mark)
Answer : B-DNA

32. Tools used in the formation of recombinant DNA are of three types. These are enzymes cloning vectors and competent host. Lysing enzymes are used to extract DNA for experimental purpose from the cells. Cleaving enzymes break the DNA molecules. They are of three types: exonucleases, endonucleases and restriction endonucleases. A competent host is required for transformation with recombinant DNA and cloning vectors help to propagate DNA.
Questions :
(a) What are cloning vectors? (2 Marks)
Answer – Cloning vectors are DNA molecules used to carry foreign genetic material into a host cell, where it can be replicated and/or expressed. Examples of cloning vectors include plasmids, bacteriophages, cosmids, and artificial chromosomes (such as BACs and YACs).

(b) Transfer of DNA into eukaryotic cell is called …………….. (1 Mark)
Answer – Transfection

(c) Enzymes used in R-DNA technology are …………… (1 Mark)
Answer – Enzymes used in recombinant DNA (R-DNA) technology include : Exonucleases, Endonucleases, Restriction endonucleases, Ligases, Polymerases.

Section – E (5 Marks)

33. Describe the structure of human sperm.
Answer – The sperm is the male gamete produced in the testes of the male reproductive system. It consists of three parts – head, middle piece and the tail. The sperm head is elongated and formed by the condensation of nucleus. The anterior portion has a cap like structure called acrosome. It contains hyaluronidase an enzyme that helps the sperm to enter the ovum during fertilization. A short neck connects the head and middle piece which comprises that centrioles. The middle piece contains the mitochondria which provides energy for the movement of tail. It brings about sperm motility which is essential for fertilization.

34. What is semi conservative mode of replication? Explain Messelson and Stahl experiment to prove semi conservative replication?
Answer – During DNA replication each newly synthesized DNA has one parental strand and one newly synthesized strand. This is called semi conservative replication. Since nitrogen is a part of DNA so Stahl and Messelson use heavy nitrogen in place of normal nitrogen
(a) Meselson and Stahl grew E.coli on heavy Nitrogen isotope for many generations. So that N¹⁵ is incorporated into its DNA. Then transferred E.coli to medium containing N¹⁴ and allow them to grow.
(b) The DNA in first generation has intermediate density as compared to parental DNA. The density was measured by cesium chloride density gradient method
(c) DNA in second generation has half normal density and half intermediate density DNA strand. This shows semi conservative replication.

35. Define Decomposition and describe the process and products of decomposition.
Answer – Decomposition is the process of breakdown of complex organic matter into inorganic substances so that they can be reused.
The important steps in the process of decomposition are :
(i) Fragmentation – Breakdown of detritus (dead plant remains and dead remains of animals) into smaller particles by detritivores (e.g., earthworm).
(ii) Leaching – Water soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts.
(iii) Catabolism – Bacterial and fungal enzymes degrade detritus into simpler inorganic substances.
(iv) Humification – Accumulation of a dark-coloured amorphous substance.
(v) Mineralisation – Humus is further degraded by some microbes and release of inorganic nutrients.
Products of decomposition are carbon dioxide, water and nutrients.

 

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