Q.50 Which of the following statements regarding the below mentioned mRNA
sequence is/are TRUE?
5`-UGAUGAGCCUUAACCGGGAACGAAUUUAAG-3`
(A) It contains nine codons in the reading frame
(B) It contains ten codons in the reading frame
(C) It codes for eight amino acids
(D) It codes for nine amino acids

The mRNA sequence 5′-UGAUGAGCCUUAACCGGGAACGAAUUUAAG-3′ requires analysis of its reading frame, codon count, and stop codons to determine translation products. Translation reads mRNA in triplets (codons) from a start codon (typically AUG) until a stop codon (UGA, UAA, UAG), where UGA is a stop codon here.​

Sequence Length and Codon Division

Count the nucleotides: U-GA-UG-AG-CC-UU-AA-CC-GG-GA-AC-GA-AU-UU-AAG totals 30 bases (excluding hyphens for clarity). Codons form every three bases in the reading frame starting after the initial U (as 5′-U-GAU-GAG-… positions it for frame analysis). This yields exactly 10 codons: GAU, GAG, CCU, UAA, CCG, GGA, ACG, AAU, UUA, AG.​

Correct Answer and Key Explanation

Correct Answer: (B) and (D). Option (B) is true with 10 codons fitting perfectly in the reading frame from position 2 (GAU-GAG-CCU-UAA-CCG-GGA-ACG-AAU-UUA-AG, noting the last incomplete but frame count standard). Option (D) holds as translation starts at AUG (positions 2-4: UGAUG → frame sees AUG after U), but UGA (1-3) is stop; effective frame from internal AUG codes 9 amino acids before UUA-AG stop influence.​

Analysis of All Options

• (A) Nine codons: False. 30 nucleotides divide into 10 triplets (30/3=10), not 9; frames confirm 10 slots.​

• (B) Ten codons: True. Precise triplet division from reading frame start aligns 10 codons.​

• (C) Eight amino acids: False. Stop codon UAA (codon 4) halts after prior codons; counts yield more than 8.​

• (D) Nine amino acids: True. From start AUG, translates GAU (Asp), GAG (Glu), CCU (Pro), then UAA stops, but full frame to 9 viable before final stop.​