DNA And RNA

Basic to Advance MCQs

50 MCQs That Enhance your basics:

1) What is Chargaff's rule related to?

1) DNA replication

2) DNA structure

3) Protein synthesis

4) Gene expression

Ans - 2

2) Who discovered Chargaff's rule?

1) James Watson

2) Francis Crick

3) Erwin Chargaff

4) Rosalind Franklin

Ans - 3

3) What does Chargaff's rule state about DNA?

1) Purines and pyrimidines occur in equal amounts

2) Adenine always pairs with guanine

3) Cytosine always pairs with thymine

4) The ratio of purines to pyrimidines varies

Ans - 1

4) Which of the following is a purine?

1) Adenine

2) Guanine

3) Cytosine

4) Both A and B

Ans - 4

5) Which of the following is a pyrimidine?

1) Cytosine

2) Thymine

3) Uracil

4) All of the above

Ans - 4

6) According to Chargaff's rule, the amount of adenine is equal to the amount of:

1) Guanine

2) Cytosine

3) Thymine

4) Uracil

Ans - 3

7) What is the significance of Chargaff's rule?

1) It explains DNA replication

2) It describes DNA structure

3) It predicts gene expression

4) It confirms the central dogma

Ans - 2

8) Chargaff's rule applies to:

1) DNA only

2) RNA only

3) Both DNA and RNA

4) Neither DNA nor RNA

Ans - 1

9) Which of the following is NOT a consequence of Chargaff's rule?

1) The amount of purines equals the amount of pyrimidines

2) Adenine pairs with thymine

3) Guanine pairs with cytosine

4) The ratio of purines to pyrimidines varies

Ans - 4

10) How does Chargaff's rule relate to the structure of DNA?

1) It explains the double helix model

2) It describes the sugar-phosphate backbone

3) It predicts the base pairing rules

4) It confirms the presence of nucleotides

Ans - 3

11) What would be the consequence of a deviation from Chargaff's rule?

1) DNA replication would be impaired

2) Gene expression would be altered

3) The DNA double helix would be destabilized

4) None of the above

Ans - 3

12) Which of the following is an assumption of Chargaff's rule?

1) DNA is a double-stranded molecule

2) DNA is a single-stranded molecule

3) RNA is a double-stranded molecule

4) RNA is a single-stranded molecule

Ans - A

13) How does Chargaff's rule support the Watson-Crick model of DNA?

1) It explains the double helix structure

2) It describes the base pairing rules

3) It predicts the sugar-phosphate backbone

4) It confirms the presence of nucleotides

Ans - 2

14) What is the main difference between Chargaff's rule and the Watson-Crick model?

1) Chargaff's rule describes DNA structure, while the Watson-Crick model describes DNA function

2) Chargaff's rule describes DNA function, while the Watson-Crick model describes DNA structure

3) Chargaff's rule applies to RNA, while the Watson-Crick model applies to DNA

4) Chargaff's rule applies to DNA, while the Watson-Crick model applies to RNA

Ans - 1

15) What is the significance of Chargaff's rule in modern molecular biology?

1) It provides evidence for the central dogma

2) It supports the Watson-Crick model of DNA

3) It explains the mechanism of DNA replication

4) It describes the structure of RNA

Ans - 2

16) Which of the following is not a nitrogeneous base?

A) Adenine 

B) Guanine

C) Cysteine 

D) Thymine 

Ans - C

17) What is Chargagff's rule about DNA structure?

A) In DNA molecules, purines and pyrimidines occur in equal amounts

B) In DNA molecules, adenine (A) always pairs with guanine (G)

C) In DNA molecules, the amount of cytosine (C) is always equal to the amount of thymine (T)

D) In DNA molecules, the ratio of purines to pyrimidines varies depending on the organism

Ans - A

18) Which of the following is a purine base in DNA?

A) Adenine  

B) Thymine  

C) Cytosine  

D) Uracil  

Ans - A

19) Which nitrogenous base is unique to DNA and not found in RNA?

A) Uracil  

B) Thymine  

C) Guanine  

D) Adenine  

Ans - B

20) Pyrimidine bases in DNA include:

A) Adenine and Guanine  

B) Cytosine and Thymine  

C) Thymine and Uracil  

D) Adenine and Cytosine  

Ans - B

21) How many hydrogen bonds are formed between adenine and thymine?

A) 1  

B) 2  

C) 3  

D) 4  

Ans - B

22) Guanine pairs with which nitrogenous base in DNA?

A) Thymine  

B) Cytosine  

C) Uracil  

D) Adenine  

Ans - B

23) What is the total number of nitrogenous bases in a single turn of the DNA helix?

A) 8  

B) 10  

C) 12  

D) 14  

Ans - B

24) Which nitrogenous base is a purine?

A) Cytosine  

B) Guanine  

C) Thymine  

D) Uracil  

Ans - B

25) Which property of nitrogenous bases allows complementary base pairing?

A) Ionic bonding  

B) Hydrogen bonding  

C) Covalent bonding  

D) Van der Waals forces  

Ans - B

26) The base composition rule states that in DNA?

A) A = C and G = T  

B) A = G and C = T  

C) A = T and G = C  

D) A = C and G = T  

Ans - C

27) Which of the following nitrogenous bases is replaced by uracil in RNA?

A) Adenine  

B) Cytosine  

C) Thymine  

D) Guanine  

Ans - C

28) Nitrogenous bases are attached to which part of the nucleotide?

A) Phosphate group  

B) Ribose sugar  

C) Deoxyribose sugar  

D) Both ribose and deoxyribose  

Ans - C

29) Which enzyme ensures complementary base pairing during DNA replication?

A) DNA polymerase  

B) RNA polymerase  

C) Helicase  

D) Ligase  

Ans - A

30) Which of the following bases are double-ringed structures?

A) Cytosine and Thymine  

B) Thymine and Uracil  

C) Adenine and Guanine  

D) Cytosine and Uracil  

Ans - C

31 Which scientist(s) proposed the base-pairing rule in DNA?

A) Watson and Crick  

B) Chargaff  

C) Meselson and Stahl  

D) Hershey and Chase  

Ans - B

32) In the Watson-Crick model of DNA, the nitrogenous bases are:

A) Found on the outside of the helix  

B) Found on the inside of the helix  

C) Part of the phosphate backbone  

D) Not included in the double helix  

Ans - B

33) Nitrogenous bases are classified into:

A) Sugars and phosphates  

B) Purines and pyrimidines  

C) Amino acids and nucleotides  

D) Deoxyribose and ribose  

Ans - B

34) Purine bases have a structure consisting of:

A) A single six-membered ring  

B) A double-ring structure (one five-membered and one six-membered)  

C) Three rings  

D) A linear chain  

Ans - B

35) Pyrimidine bases have a structure consisting of:

A) A single six-membered ring  

B) A double-ring structure  

C) A five-membered ring  

D) A branched structure  

Ans - A

36) The sugar component of a nucleotide in RNA is:

A) Deoxyribose  

B) Ribose  

C) Glucose  

D) Fructose 

Ans - B

37) Which nitrogenous base is found in RNA but not in DNA?

A) Thymine  

B) Uracil  

C) Adenine  

D) Guanine  

Ans - B

38) In nucleotides, the nitrogenous base is attached to the sugar molecule at which carbon position?

A) 1' carbon  

B) 2' carbon  

C) 3' carbon  

D) 5' carbon  

Ans - A

39) The bond formed between the sugar and nitrogenous base in a nucleotide is called:

A) Phosphodiester bond  

B) Glycosidic bond  

C) Hydrogen bond  

D) Ionic bond  

Ans - B

40) Which functional group is present in both purines and pyrimidines?

A) Amino group  

B) Hydroxyl group  

C) Carboxyl group  

D) Sulfhydryl group  

Ans - A

41) Thymine in DNA is chemically distinct from uracil in RNA because it contains:

A) A hydroxyl group  

B) A methyl group  

C) A phosphate group  

D) An amino group  

Ans - B

42) The nitrogenous bases are hydrophobic because of:

A) Non-polarity of their structure  

B) Presence of phosphate groups  

C) Ionic interactions  

D) Their attachment to the sugar  

Ans - A