BIOLOGY 
CHAPTER-MOLECULAR BASIS OF INHERITANCE AND VARIATION
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PART A
1. Mark the correct statement-
a) hnRNA is more stable than mRNA
b) mRNA is more stable than rRNA
c) mRNA of prokaryotes is more stable than mRNA of Eukaryotes
d) tRNA is present in cell in greater amount than mRNA

2. A nucleoside differs from a nucleotide. It lacks the:
a) Base 

b) sugar
c) Phosphate group

 d) hydroxyl group

3. Amino acylation of tRNA is essential for –
a) Replication of RNA 

b) formation of peptide bond

c) Splicing

 d) initiation of transcription

4. In Hershey and Chase experiment Bacteriophage with radio labelled protein , after centrifugation radioactivity appears in –
a) Radioactive Sulphur in pellet
b) Radioactive phosphorus in supernatant
c) Radioactive Sulphur in supernatant
d) Radioactive phosphorus in pellet

5. In a DNA strand the nucleotides are linked together by:
a) Glycosidic bonds 

b) phosphodiester bonds
c) peptide bonds 

d) hydrogen bonds

6. The fact that a purine base always paired through hydrogen bonds with a pyrimidine base leads to, in the DNA double helix:
a) the antiparallel nature
b) the semiconservative nature
c) uniform width throughout DNA
d) uniform length in all DNA

7. Which codon is not an indicator of completion of protein synthesis?
a) UAG

 b) AUG

 c) UAA 

d) UGA

8. If the sequence of bases in the coding strand of a double-stranded DNA is 5′-GTTCGAGTC-3′ the sequence of bases in its transcript will be –
a) 5′-GACUCGAAC-3′ 

b) 5′-CAAGCUCAG-3′
c) 5′-GUUCGAGUC-3′ 

d) 5′-CUGAGCUUG-3′

9. The first genetic material could be:
a) Protein 

b) carbohydrates 

c) DNA 

d) RNA

10. With regard to mature mRNA in eukaryotes:
a) exons and introns do not appear in the mature RNA.
b) exons appear but introns do not appear in the mature RNA.
c) introns appear but exons do not appear in the mature RNA.
d) both exons and introns appear in the mature RNA.

11. Discontinuous synthesis of DNA occurs in one strand, because:
a) DNA molecule being synthesized is very long.
b) DNA dependent DNA polymerase catalyzes polymerization only in one direction (5’ → 3’)
c) it is a more efficient process
d) DNA ligase has to have a role

12. Which of the following steps in transcription is catalyzed by RNA polymerase?
a) Initiation

 b) Elongation

 c) Termination 

d) All of the above

13. Control of gene expression takes place at the level of:
a) DNA-replication 

b) Transcription 

c) Translation 

d) Both b and c

14. Regulatory proteins are the accessory proteins that interact with RNA polymerase and affect its role in transcription. Which of the following statements is correct about regulatory protein?
a) They only increase expression
b) They only decrease expression
c) They interact with RNA polymerase but do not affect the expression
d) They can act both as activators and as repressors

15. Which of the following are the functions of RNA?
a) It is a carrier of genetic information from DNA to ribosomes synthesizing polypeptides.
b) It carries amino acids to ribosomes.
c) It is a constituent component of ribosomes.
d) All of the above.

16. While analyzing the DNA of an organism a total number of 5386 nucleotides were found out of which the proportion of different bases were: Adenine = 29%, Guanine = 17%, Cytosine = 32%, Thymine = 17%. Considering the Chargaff’s rule it can be concluded that:
a) it is a double stranded circular DNA
b) It is single stranded DNA
c) It is a double stranded linear DNA
d) No conclusion can be drawn

17. If Meselson and Stahl’s experiment is continued for four generations in bacteria, the ratio of 15N/15N : 15N/14N: 14N/14N containing DNA in the fourth generation would be:
a) 1 : 1 : 0

 b) 1 : 4 : 0

 c) 0 : 1 : 3 

d) 0 : 1 : 7

18. If the sequence of nitrogen bases of the coding strand of DNA in a transcription unit is: 5′ – A T G A A T G – 3′, the sequence of bases in its RNA transcript would be –
a) 5′ – A U G A A U G – 3′ 

b) 5′ – U A C U U A C – 3′
c) 5′ – C A U U C A U – 3′ 

d) 5′ – G U A A G U A – 3′

19. The RNA polymerase holoenzyme transcribes:
a) the promoter, structural gene and the terminator region
b) the promoter, and the
c) the structural gene and the terminator regions
d) the structural gene only.

20. If the base sequence of a codon in mRNA is 5′-AUG-3′, the sequence of tRNA pairing with it must be:
a) 5′ – UAC – 3′ 

b) 5′ – CAU – 3′

 c) 5′ – AUG – 3′ 

d) 5′ – GUA – 3′

21. The amino acid attaches to the tRNA at its:
a) 5′ – end 

b) 3′ – end 

c) Anti codon site 

d) DHU loop

22. In E.coli, the lac operon gets switched on when:
a) lactose is present and it binds to the repressor
b) repressor binds to operator
c) RNA polymerase binds to the operator
d) lactose is present and it binds to RNA polymerase

23. What is an international project that studies the genomes of humans and other organisms?
a) National Health Initiative 

b) Human Genome Project
c) International Energy Project

 d) International Genome Project

24. In eukaryotic genes, coding sequences are called –
a) introns 

b) exons
c) regulatory sequence

 d) repetitive DNA

25. Which site of the tRNA pairs through hydrogen bonding with the triplet codes on mRNA?
a) Codon 

b) 5′ end tRNA 

c) 3′ end of tRNA 

d) Anticodon

26. Find the wrongly matched pair –
a) Har Govind Khorana – Synthesized RNA molecules chemically
b) George Gamow – Codon is triplet
c) Meselson and Stahl – Regulation of gene expression
d) Alec Jeffrey’s – DNA fingerprinting

27. If an inheritable mutation is observed in a population at high frequency, it is referred as –
a) DNA polymorphism

 b) expressed sequence tag
c) sequence annotation 

d) linkage

28. In eukaryotes, RNA polymerase II transcribe
a) hn RNA 

b) 18S r RNA 

c) 28s r RNA 

d) tRNA

29. Which property among these listed below is not a criteria for a molecule to act as a genetic material?
a) Generate its replica.
b) Chemically and structurally stable.
c) Mutate slowly to facilitate evolution.
d) Destroy itself after every cell cycle.

30. Statement I: In prokaryotes, the positively charged DNA is held with some negatively charged proteins in a region called nucleoid.
Statement II: In eukaryotes, the negatively charged DNA is wrapped around the positively charged histone octamer to form nucleosome.
a) Both Statement I and Statement II are false.
b) Statement I is correct but Statement II is false.
c) Statement I is incorrect but Statement II is true.
d) Both Statement I and Statement II are true.

31. Assertion (A): One codon may code for more than one amino acid.
Reason (R): A codon is degenerate and unambiguous.
a) Both Assertion (A) and Reason (R) are the true, and Reason (R) is a correct explanation of Assertion (A).
b) Both Assertion (A) and Reason (R) are the true, but Reason (R) is not a correct explanation of Assertion (A).
c) Assertion (A) is true, and Reason (R) is false.
d) Assertion (A) is false, and Reason (R) is true.

32. Calculate the length of DNA sample, if it had 240 bp;
a) 340 Å 

b) 816 Å 

c) 1024 Å 

d) 120 Å

33. A DNA molecule in which both strands have radioactive thymidine is allowed to duplicate in an environment containing non-radioactive thymidine. What will be the exact number of DNA molecules that contains the radioactive thymidine after three duplications?
a) One 

b) Two 

c) Four

 d) Eight

34. How many amino acids will be coded by the mRNA sequence 5’ –CCUCAUAGUCAUAC-3’, if one adenosine residue is inserted after every 12th nucleotide?
a) Five amino acids 

b) Six amino acids
c) Two amino acids

 d) three amino acids

35. The Severo Ochoa enzyme is;
a) DNA polymerase.

 b) Reverse transcriptase.
c) Polynucleotide phosphorylase. 

d) DNA development DNA polymerases.

PART B

36. E. Coli has only 4.6 × 106 base pairs and completes the process of replication within 18 minutes; then the average rate of polymerization is approximately
a) 3000 base pairs/second 

b) 4000 base pairs/second
c) 1000 base pairs/second

 d) 2000 base pairs/second

37. If there are 999 bases in an RNA that codes for a protein with 333 amino acids, and the base at position 901 is deleted such that the length of the RNA becomes 998 bases, how many codons will be altered?
a) 1 

b) 11 

c) 33 

d) 333

38. Read the following four statements (A – D)
(A) In transcription, adenosine pairs with uracil.
(B) Regulation of lac operon by repressor is referred to as positive regulation.
(C) The human genome has approximately 50,000 genes.
(D) Haemophilia is a sex-linked recessive disease.

How many of the above statements are right?
a) Two b) Three c) Four d) One

39. Consider the following statements and choose the correct option: (2017-Gujarat)
(a) six codons do not code for any amino–acid
(b) codon is read in mRNA in a contiguous fashion
(c) three codons function as stop codons
(d) the initiator codon AUG codes for methionine
a) (a) is wrong

b) (a)(b) and (d) are wrong

c) (a), (b) and (c) are wrong 

d) (b), (c) and (d) are wrong

40. Mark the incorrect statement-
a) promoter is located upstream in respect of coding strand
b) rRNA have structural and catalytically role in translation
c) rRNA is synthesize by RNA polymerase in bacteria
d) Genetic code was postulated before tRNA discovered

41. How many are correctly matched –
(a) between two Nucleoside- phosphodiester linkage present
(b) tRNA- functional in two degree
(c) lac operon – inducible operon
(d) Okazaki fragment – made up of RNA
a) four 

b) three 

c) one

 d) two

42. Consider the following statements-
(a) Histones are double in s-phase
(b) RNA polymerase II synthesizes hnRNA
How many statements are correct?
a) Only A 

b) both A and B 

c) only 2 

d) neither A nor B

43. Mark the incorrect statement-
a) Primer synthesize in 5’ to 3’ direction on both leading and lagging strand
b) DNA dependent polymerase always polymerize in 5’ to 3’ direction
c) Leading strand show DNA replication in 5’ to 3’ direction and lagging in 3’ to 5’ direction
d) Ligase catalyzed phosphodiester bond formation

44. Mark the incorrect statement-
a) DNA is chemically less reactive than RNA
b) DNA is structurally more stable than RNA
c) DNA is not catalytically active
d) RNA is catalytically inactive

45. Which of the following is not according to Chargaff?
a) A/T = G/C 

b) A+G / T+C

 c) A/G = T/C

 d) A+T /G+C

46. A – Stability as a property of genetic material was very evident in Griffith’s transforming principle.
R – Heat can kill the bacteria and completely destroy the properties of genetic material
a) Both A and R are true and R is correct explanation for A
b) Both A and R are true but R is not correct explanation for R
c) A is true but R is false
d) Both A and R are false

47. If the gene encoding the lac repressor is mutated so that it can no longer bind the operator, will transcription of that operon occur?
a) Yes, but only when lactose is present.
b) No, because RNA polymerase is need to transcribe the genes.
c) Yes, because the operator will not be bound by repressor and RNA polymerase can transcribe the lac operon.
d) No, because cAMP levels are low when the repressor is non-functional.

48. Consider the following statements.
I. Major countries who contributed or participated in human genome project were Japan, France, Germany and China.
II. Human genome project was a mega project of 13years.

Choose the correct option.
a) Statement I is true, but II is false 

b) Statement II is true, but I is false
c) Both statement I and II are correct

 d) both statement I and II are incorrect

49. How many codons are used to code for all the 20 essential amino acids, in the genetic code dictionary?
a) 20

 b) 64 

c) 61 

d) 60

50. Beta-galactosidase is synthesized by E.coli to catalyze hydrolysis of _______ into _________and glucose.
a) Galactose; lactose 

b) Galactose; glucose
c) Lactose; galactose 

d) maltose; galactose

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ANSWER KEY- MOLECULAR BASIS OF INHERITANCE
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