Question

The sequence of nucleotides of mRNA and the sequence of respective amino acids in the polypeptide chain is given below. \[ \begin{aligned} \text{mRNA: }&\text{AUG UUU AUG CCU GUU UAA} \text{Polypeptide: }&\text{Met \quad Phe \quad Met \quad Pro \quad Val} \end{aligned} \] The nucleotide sequence of DNA template strand from which this mRNA was transcribed is

• A. TAC AAA TAC GGA CAA ATT
• B. AUG UUU AUG CCU GUU UAA
• C. UAC AAA UAC GGA CAA AUU
• D. ATG TTT ATG CCT GTT TAA

Hint:

While obtaining the DNA template from mRNA, use complementary pairing: \[ \boxed{ A\leftrightarrow T,\qquad U\leftrightarrow A,\qquad G\leftrightarrow C,\qquad C\leftrightarrow G. } \]

Answer 1

The Correct Option is A

Step 1: Write the complementary DNA template sequence. The DNA template strand is complementary to mRNA. \[ \begin{array}{c|c} \text{mRNA} & \text{DNA Template} \hline A & T U & A G & C C & G \end{array} \]

Step 2: Convert each codon. \[ \begin{aligned} \text{AUG} &\rightarrow \text{TAC} \text{UUU} &\rightarrow \text{AAA} \text{AUG} &\rightarrow \text{TAC} \text{CCU} &\rightarrow \text{GGA} \text{GUU} &\rightarrow \text{CAA} \text{UAA} &\rightarrow \text{ATT} \end{aligned} \] Thus, \[ \boxed{\text{DNA template}=\text{TAC AAA TAC GGA CAA ATT}.} \]

Step 3: Choose the correct option. Hence, the correct option is \[ \boxed{(A).} \]