Question
Which diagram represents the modified mRNA after transcription?
▶️Answer/Explanation
Ans. A
-
Adding a 5′ cap and 3′ polyadenylated tail
These modifications help transport the mRNA to ribosomes and protect it from degradation.
RNA splicing
This process removes non-coding introns and links coding exons together.
N6-methyladenosine (m6A) methylation
This is one of the most common modifications to mRNA. It can affect many cellular events, including splicing, translation, and degradation.
2′-O-methylation
This modification can dramatically affect the structure and stability of RNA.
Editing of adenosine (A) to inosine (I)
This modification is also known as deamination and can strongly modulate the expression of target RNAs.
Other types of mRNA modifications include N1-methyladenosine (m1A), 5-methylcytosine (m5C), and pseudouridine.
These modifications can alter the RNA structure, which can affect how proteins bind to it. This can regulate mRNA stability and translation.
Question
The diagram shows the structure of a peptide.
How many bases are required in an mRNA molecule to code for this peptide?
A. 18
B. 36
C. 54
D. 72
▶️Answer/Explanation
Ans. C
- Identify the number of amino acids
- Calculate the number of codons
- Calculate the total number of nitrogen basesin the above question
- If a polypeptide chain has 18 amino acids, then the number of codons required is 60.
- Each codon has 3 nitrogen bases, so the total number of nitrogen bases for the amino acids is 18 x 3 = 54
Question
This DNA sequence was used to synthesize a polypeptide.
DNA (sense strand): 3′ T A C T G A 5′
DNA (template strand): 5′ A T G A C T 3′
Which are the bases of the tRNA (anticodons)?
A. T A C T G A
B. U A C U G A
C. A U G A C U
D. A T G A C T
▶️Answer/Explanation
Ans:C
Question
The image shows a polysome in a bacterial cell.
How many genes have been transcribed?
A. 1
B. 2
C. 3
D. 4
▶️Answer/Explanation
Ans:A