Describe why translation of an mrna can start before transcription of the mrna is complete in prokaryotes but not in eukaryotes.

In prokaryotes both transcription and translation occurs in cytoplasm (they lack true nucleus) while in eukaryotes, transcription occurs in nucleus while translation occurs in cytoplasm.

Explanation:

1. Prokaryotes do not have nucleus, so both transcription and translation occurs in the cytoplasm, therefor translation start before the completion of transcription.

2. While in eukaryotes, they have true nucleus, and there protein synthesis machinery (ribosomes) and is situated in the cytoplasm.

So in eukaryotes transcription occurs in the nucleus, and after the completion of transcription, mRNA is processed and finally export into cytoplasm for translation.