Question

What among the following is correct in eukaryotes and prokaryotes?

• A. mRNA is polycistronic in eukaryotes and monocistronic in prokaryotes.
• B. mRNA is polycistronic in both eukaryotes and prokaryotes.
• C. mRNA is monocistronic in both eukaryotes and prokaryotes.
• D. mRNA is polycistronic in prokaryotes and monocistronic in eukaryotes.

Answer 1

Answer: (D)

mRNA is polycistronic in prokaryotes and monocistronic in eukaryotes.

Most of the prokaryotic mRNAs are polycistronic which means that multiple genes are present on a single transcript and the single promoter initiates transcription of all those genes and regulates their expression. They have multiple initiation and termination codons and thus translate more than one protein. This makes option C wrong. Eukaryotic mRNAs are monocistronic which are transcribed from a single gene and thus carry single initiation and termination codons thereby coding for a single polypeptide. This makes options A and B wrong as polycistronic mRNAs are not found in eukaryotes. The correct option is D.