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12th Standard Bio-Zoology English Medium Evolution Reduced Syllabus Important Questions With Answer Key 2021

12th Standard

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Biology

Time : 01:00:00 Hrs
Total Marks : 100

    Multiple Choice Questions

    15 x 1 = 15
  1. What is the basis for the difference in the synthesis of the leading and lagging strand of DNA molecules?

    (a)

    Origin of replication occurs only at the 5' end of the molecules

    (b)

    DNA ligase works only in the 3' → 5' direction

    (c)

    DNA polymerase can join new nucleotides only to the 3' end of the growing stand.

    (d)

    Helicases and single-strand binding proteins that work at the 5' end

  2. Which of the following is the correct sequence of event with reference to the central dogma?

    (a)

    Transcription, Translation, Replication

    (b)

    Transcription, Replication, Translation

    (c)

    Duplication, Translation, Transcription

    (d)

    Replication, Transcription, Translation

  3. Which of the following statements about DNA replication is not correct?

    (a)

    Unwinding of DNA molecule occurs as hydrogen bonds break.

    (b)

    Replication occurs as each base is paired with another exactly like it

    (c)

    Process is known as semi conservative replication because one old strand is conserved in the new molecule.

    (d)

    Complementary base pairs are held together with hydrogen bonds

  4. Which of the following statements is not true about DNA replication in eukaryotes?

    (a)

    Replication begins at a single origin of replication.

    (b)

    Replication is bidirectional from the origins.

    (c)

    Replication occurs at about 1 million base pairs per minute

    (d)

    There are numerous different bacterial chromosomes, with replication ocurring in each at the same time.

  5. An operon is a:

    (a)

    Protein that suppresses gene expression

    (b)

    Protein that accelerates gene expression

    (c)

    Cluster of structural genes with related function

    (d)

    Gene that switched other genes on or off

  6. When lactose is present in the culture medium:

    (a)

    Transcription of lac y, lac z, lac a genes occurs.

    (b)

    Repressor is unable to bind to the operator.

    (c)

    Repressor is able to bind to the operator.

    (d)

    Both (a) and (b) are correct.

  7. One gene one enzyme hypothesis was proposed by Beadle and Tatum based on ________

    (a)

    Yeast

    (b)

    Drosophila

    (c)

    E. coli

    (d)

    Neurospora

  8. Chromosomes were first observed by ________.

    (a)

    Miescher

    (b)

    Hofmeister

    (c)

    Avery

    (d)

    Griffith

  9. ___________ used radioactive labelled molecules to prove that DNA is the genetic material.

    (a)

    Hershey and Chase

    (b)

    Wilkins and Franklin

    (c)

    Griffith

    (d)

    Mcleod and Avery

  10. One difference between deoxyribose and Ribose is due to________.

    (a)

    One Oxygen atom more in Ribose

    (b)

    Two Oxygen atoms less in Deoxyribose

    (c)

    Two Carbon atoms less in Ribose

    (d)

    Four Carbon atoms more in Ribose

  11. The concept of RNA world was independently proposed by __________

    (a)

    Orgel, Brick and Carl woese

    (b)

    Brick, Griffith and Crick

    (c)

    Wilkins and Franklin

    (d)

    Walter Gilbert

  12. The distance between two consecutive base pairs in DNA is_________.

    (a)

    3.4 nm

    (b)

    0.34 nm

    (c)

    34.0nm

    (d)

    31x10-9

  13. A nucleosome has _________ histone protein molecules.

    (a)

    6

    (b)

    8

    (c)

    10

    (d)

    24

  14. In genetic code there are __________ possible triplets.

    (a)

    62

    (b)

    61

    (c)

    68

    (d)

    64

  15. The codon _________ codes for phenylalanine

    (a)

    UAA

    (b)

    UUU

    (c)

    UCU

    (d)

    UAC

  16. 2 Marks

    10 x 2 = 20
  17. Give reasons: Genetic code is ‘universal’.

  18. Name the parts marked ‘A’ and ‘B’ in the given transcription unit:

  19. Differentiate - Template strand and coding strand.

  20. Mention any two ways in which single nucleotide polymorphism (SNPs) identified in human genome can bring revolutionary change in biological and medical science

  21. State any three goals of the human genome project.

  22. In E.coli, three enzymes β- galactosidase, permease and transacetylase are produced in the presence of lactose. Explain why the enzymes are not synthesized in the absence of lactose.

  23. What are nucleotides?

  24. What is genophore?

  25. Point out the nitrogenous bases of RNA

  26. Which type of bond is formed
    (a) between a purine and pyrimidine base?
    (b) between the pentose sugar and adjacent nucleotide?

  27. 3 Marks

    10 x 3 = 30
  28. Distinguish between structural gene, regulatory gene and operator gene

  29. Why the human genome project is called a mega project?

  30. From their examination of the structure of DNA, What did Watson and Crick infer about the probable mechanism of DNA replication, coding capability and mutation?

  31. Distinguish replication and transcription.

  32. What is initiation complex in transcription?

  33. What is a anticodon?

  34. What is S-D Sequence?

  35. State Chargaff's rule.

  36. Both strands of DNA are not copied during transcription. Give reason.

  37. Explain the components of operon.

  38. 5 Marks

    7 x 5 = 35
  39. a) Identify the figure given below
    b) Redraw the structure as a replicating fork and label the parts
    c) Write the source of energy for this replication and name the enzyme involved in this process.
    d) Mention the differences in the synthesis of protein, based on the polarity of the two template strands.

  40. How is the two stage process of protein synthesis advantageous?

  41. It is established that RNA is the first genetic material. Justify giving reasons.

  42. List the salient features of classical concept of gene.

  43. Meselson and Stahl's experiment proved the semi-conservation mode of DNA replication. Explain.

  44. Mutations on genetic code affects the phenotype. Describe with example.

  45. Draw a flow chart depicting the steps of DNA fingerprinting technique.

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