Question

Which of the following statements is correct ? A. Intercalating agents distort DNA to induce single nucleotide pair insertions and deletions.
B. T and G typically exist in the amino form and A and C in the keto form.
C. Base analogues are structurally similar to normal nitrogenous bases.
D. Point mutations are mutations that occur at specific positions.
E. Nonsense mutations convert a sense codon to a stop codon.
Choose the correct answer from the options given below :

• A. \(A, B\) only
• B. \(B, D\) only
• C. \(A, C, E\) only
• D. \(C, D\) only

Hint:

Remember:
• Intercalating agents \(\rightarrow\) Frameshift mutations
• Base analogues \(\rightarrow\) Resemble normal bases
• Nonsense mutation \(\rightarrow\) Produces stop codon Normal tautomeric forms: \[ A,C \rightarrow \text{Amino} \] \[ G,T \rightarrow \text{Keto} \]

Answer 1

The Correct Option is C

Concept: Mutations are heritable changes in the genetic material. Different mutagens and mutation types affect DNA in distinct ways. Important concepts include:
• Intercalating agents causing frameshift mutations
• Base analogues resembling normal bases
• Nonsense mutations generating stop codons

Step 1: Evaluating statement A. Statement A: \[ \text{Intercalating agents induce insertions and deletions} \] This is correct. Intercalating agents such as:
• Acridine orange
• Ethidium bromide insert between DNA base pairs and may cause: \[ \text{Single nucleotide insertions or deletions} \] leading to frameshift mutations. Thus: \[ \boxed{A \text{ is correct}} \]

Step 2: Evaluating statement B. Statement B: \[ \text{T and G exist in amino form and A and C in keto form} \] This is incorrect. Normally: \[ \text{Adenine and Cytosine} \rightarrow \text{Amino form} \] \[ \text{Guanine and Thymine} \rightarrow \text{Keto form} \] Thus: \[ \boxed{B \text{ is incorrect}} \]

Step 3: Evaluating statement C. Statement C: \[ \text{Base analogues are structurally similar to normal bases} \] This is correct. Examples:
• 5-bromouracil
• 2-aminopurine These compounds resemble normal nitrogenous bases and may cause mispairing during replication. Thus: \[ \boxed{C \text{ is correct}} \]

Step 4: Evaluating statement D. Statement D: \[ \text{Point mutations occur at specific positions} \] This statement is considered incorrect in this context. Point mutations specifically refer to: \[ \text{Change in a single nucleotide base pair} \] rather than simply mutations occurring at a specific position. Thus: \[ \boxed{D \text{ is incorrect}} \]

Step 5: Evaluating statement E. Statement E: \[ \text{Nonsense mutations convert a sense codon to a stop codon} \] This is correct. As a result: \[ \text{Premature termination of protein synthesis occurs} \] Thus: \[ \boxed{E \text{ is correct}} \] Therefore, the correct statements are: \[ \boxed{A, C, E} \] Hence, the correct answer is: \[ \boxed{(C)\ A, C, E \text{ only}} \]