How does protein processing differ in prokaryotes and eukaryotes?

How does protein processing differ in prokaryotes and eukaryotes?

• A. Transcription and translation occur concurrently in prokaryotes
• B. All eukaryotic mRNA transcripts are immediately translated
• C. Prokaryotes have a nucleus
• D. Eukaryotes do not modify RNA after transcription

Answer: (A)

Transcription and translation are tightly linked in prokaryotes because there is no nucleus to separate them. As RNA polymerase is synthesizing mRNA, ribosomes can immediately attach to the nascent transcript and start translating it. This concurrent processing means protein production can begin even while the message is still being formed, and folding or targeting signals can act on proteins as they emerge. In contrast, eukaryotes keep transcription in the nucleus, where the primary RNA transcript undergoes processing—adding a 5' cap, a poly(A) tail, and splicing—before the mature mRNA is exported to the cytoplasm for translation. Because of this spatial and temporal separation, protein production in eukaryotes is not directly coupled to transcription. The other statements don’t fit because eukaryotic RNA transcripts are not all immediately translated (they require processing), prokaryotes lack a nucleus, and eukaryotes do modify RNA after transcription.

Transcription and translation are tightly linked in prokaryotes because there is no nucleus to separate them. As RNA polymerase is synthesizing mRNA, ribosomes can immediately attach to the nascent transcript and start translating it. This concurrent processing means protein production can begin even while the message is still being formed, and folding or targeting signals can act on proteins as they emerge.

In contrast, eukaryotes keep transcription in the nucleus, where the primary RNA transcript undergoes processing—adding a 5' cap, a poly(A) tail, and splicing—before the mature mRNA is exported to the cytoplasm for translation. Because of this spatial and temporal separation, protein production in eukaryotes is not directly coupled to transcription.

The other statements don’t fit because eukaryotic RNA transcripts are not all immediately translated (they require processing), prokaryotes lack a nucleus, and eukaryotes do modify RNA after transcription.