Subject: Biology
Class XII
Time Allowed: 3 hours
Max Marks: 70
General Instructions:
1. The Question Paper contains five sections.
2. Section A has 21 questions of 1 mark each. All questions are based on multiple choice questions.
3. Section B has 14 questions of 1 mark each. All questions are based on very short questions and objective type.
4. Section C has 04 questions of 2 marks each.
5. Section D has 04 questions of 3 marks each
6. Section E has 03 questions of 5 marks each.
6. There is no negative marking
SECTION – A
1. Polycistronic messenger RNA (mRNA) usually occurs in
(a) bacteria
(b) prokaryotes
(c) eukaryotes
(d) both (a) and (b)
2. Urethral meatus refers to the
(a) urinogenital duct
(b) opening of vas deferens into urethra
(c) external opening of the urinogenital duct
(d) muscles surrounding the urinogenital duct.
3. Trisomy is represented by
(a) (2n – 1)
(b) (2n – 2)
(c) (2n + 2)
(d) (2n + 1)
4. Transcription unit
(a) starts with TATA box
(b) starts with pallendrous regions and ends with rho factor.
(c) starts with promoter region and ends in terminator region
(d) starts with CAAT region
5. Which of the following are reasons for Mendel’s success ?
(i) Usage of pure lines or pure breeding varieties
(ii) Consideration of one character at a time
(iii) Maintenance of statistical records of experiments
(iv) Knowledge of linkage and incomplete dominance
(a) (i) and (ii) only
(b) (i), (ii) and (iii)
(c) (i) and (iv) only
(d) (ii), (iii) and (iv)
6. If the sequence of bases in DNA is GCTTAGGCAA then the sequence of bases in its transcript will be
(a) GCTTAGGCAA
(b) CGAATCCGTT
(c) CGAAUCCGUU
(d) AACGGAUUCG.
7. Which three scientists independently rediscovered Mendel’s work?
(a) Avery, McLeod, McCarty
(b) Sutton, Morgan and Bridges
(c) Bateson, Punnet and Bridges
(d) de Vries, Correns and Tschemark
8. Amino acid acceptor end of tRNA lies at
(a) 5’ end
(b) 3’ end
(c) T VC loop
(d) DHU loop.
9. Both chasmogamous and cleistogamous flowers are present in
(a) Helianthus
(b) Commelina
(c) Rosa
(d) Gossypium
10. Some amino acids are coded by more than one codon, hence the genetic code is
(a) overlapping
(b) degenerate
(c) wobbled
(d) unambiguous.
11. Which of the following is correct for the condition when plant YyRr is back crossed with the double recessive parent ?
(a) 9 : 3 : 3 : 1 ratio of phenotypes only
(b) 9 : 3 : 3 : 1 ratio of genotypes only
(c) 1 : 1 : 1 : 1 ratio of phenotypes only
(d) 1 : 1 : 1 : 1 ratio of phenotypes and genotypes
12. Find out the wrong statement about heterochromatin,
(a) It is densely packed
(b) It stains dark.
(c) It is transcriptionally active.
(d) It is late replicating.
13. Which of the following is not a water pollinated plant?
(a) Zostera
(b) Vallisneria
(c) Hydrilla
(d) Cannabis
14. Histone proteins are
(a) basic, negatively charged
(b) basic, positively charged
(c) acidic, positively charged
(d) acidic, negatively charged
15. Select the incorrect statement regarding pedigree analysis.
(a) Solid symbols show unaffected individuals.
(b) Proband is the person from which case history starts.
(c) It is useful for genetic counsellors.
(d) It is an analysis of traits in several generations of a family.
16. Amminocentesis is a technique used to
(a) determine errors in amino acid metabolism in embryo
(b) pin point specific cardiac ailments in embryo
(c) determine any hereditary genetic abnormality in embryo
(d) all of these.
17. How far is each base pair from the next one in DNA double helix model?
(a) 2 nm
(b) 3.4 nm
(c) 34 nm
(d) 0.34 nm
18. Which part of the sperm plays an important role in penetrating the egg membrane?
(a) Allosome
(b) Tail
(c) Autosome
(d) Acrosome
19. If a double stranded DNA has 20% of cytosine, what will be the percentage of adenine in it?
(a) 20%
(b) 40%
(c) 30%
(d) 60%
20. Which of the following is incorrect regarding ZW – ZZ type of sex determination?
(a) It occurs in birds and some reptiles.
(b) Females are homogametic and males are heterogametic.
(c) 1:1 sex ratio is produced in the offsprings.
(d) All of these
21. Male and female flowers are present on different plants (dioecious) to ensure xenogamy, in
(a) papaya
(b) bottle gourd
(c) maize
(d) all of these.
SECTION – B
22. AaBb was crossed with aabb. What would be the phenotypic ratio of the progeny? Mention the term used to donate this kind of cross.
23. Name the linkage connecting the two nucleotides.
24. A haemophilic man marries a normal homozygous woman. What is the probability that their daughter will be haemophilic?
25. How many pollen grains and ovules are likely to be formed in the anther and the ovary of an angiosperm bearing 25 microspore mother cells and 25 megaspore mother cells respectively?
26. Which one of an Intron or an Exon is the reminiscent of antiquity?
27. Name the negatively charged and positively charged components of a nucleosome.
28. Name any one plant & its feature that shows the phenomena of incomplete dominance?
29. A bilobed, dithecous anther has 100 microspore mother cells per microsporangium. How many male gametophytes this anther can produce?
30. Two claimant fathers filed a case against a lady claiming to be the father of her only daughter. How could this case be settled by identifying the real biological father?
31. Name the metabolism or enzyme that is impaired in phenylketonuria?
Read the Assertion and Reason carefully to mark the correct option out of the options given below:
32. Assertion: Enzymes required for DNA replication are efficient enzymes
Reason: They can polymerise large number of nucleotides in very short time
(a) If both the Assertion and the Reason are true and the Reason is a correct explanation of the Assertion.
(b) If both the Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.
(c) If the Assertion is true but the Reason is false.
(d) If both the Assertion and Reason are false
33. Assertion: The bulbourethral gland is a male accessory gland.
Reason: Its secretion helps in the lubrication of the penis, thereby facilitating reproduction.
(a) If both the Assertion and the Reason are true and the Reason is a correct explanation of the Assertion.
(b) If both the Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.
(c) If the Assertion is true but the Reason is false.
(d) If both the Assertion and Reason are false
34. Assertion: Infundibulum is a funnel shaped part closer to ovary.
Reason: The edges of infundibulum helps in collection of the ovum after ovulation.
(a) If both the Assertion and the Reason are true and the Reason is a correct explanation of the Assertion.
(b) If both the Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.
(c) If the Assertion is true but the Reason is false.
(d) If both the Assertion and Reason are false
35. Assertion: The genetic codes are commaless.
Reason: Genetic codes are overlapping.
(a) If both the Assertion and the Reason are true and the Reason is a correct explanation of the Assertion.
(b) If both the Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.
(c) If the Assertion is true but the Reason is false.
(d) If both the Assertion and Reason are false
SECTION – C
36. Three codons on mRNA are not recognized by tRNA. What are they? What is the general term used for them and what is their significance in protein synthesis?
37. The map distance between a certain organisms genes A and B is 4 units, between B and C is 5 units and between C and D is 8 units. Which one of the gene pairs will show more recombination frequency? Give reason.
38. Mention Any Four Objectives of RCHC.
39. What is the reason for the absence of menstrual cycles during conception or pregnancy?
SECTION – D
40. Why is breastfeeding recommended during the initial stages of infant growth?
41. Define bacterial transformation? Who proved it experimentally & how?
42. Draw a labeled diagram of mature embryo sac & label the following i) Egg cell ii) Antipodal cells iii) Synergids iv) Polar nuclei
OR
Draw a diagram of L.S. of an anatropous ovule of an Angiosperm & label the following parts: – (i) Nucleus (ii) Integument (iii) Antipodal cells (iv) Secondary Nucleus.
43. A colour-blind father has a daughter with normal vision. The daughter marries a man with a normal vision. What is the probability of her children to be colour blind? Explain with the help of a pedigree chart.
SECTION – E
44. Answer the following questions based on Meselson and Stahl s experiment:
(a) Write the name of the chemical substance used as a source of nitrogen in the experiment by them.
(b) Why did the scientists synthesise the light and the heavy DNA molecules In the organism used in the experiment?
(c) How did the scientists make it possible to distinguish the heavy DNA molecule from the light DNA molecule? Explain.
(d) Write the conclusion the scientists arrived at after completing the experiment.
(e) If Meselson and Stahl experiment is continued for 4 generations in E. coli, then what would be the ratio of 15N/15N:15N/14N:14N/14N.
45. Write the function of each of the following
(i) Seminal vesicle (ii) Scutellum (iii) Acrosome of human sperm (iv) corona radiata of ovum (v) LH and FSH in male
OR
Describe the post-zygotic events leading to implantation and placenta formation in humans. Mention any two functions of placenta.
46. Study the pattern of inheritance and answer the questions given: –
1. Give all the possible genotypes of the members 4, 5 and 6 in the pedigree chart.
2. A blood test shows that the individual 14 is a carrier of haemophilia. The member numbered 15 has recently married the member numbered 14. What is the probability that their first child will be a haemophilic male?
