{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Transcription and Processing of mRNA

Transcription and Processing of mRNA - unusual base is...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
Transcription and Processing of mRNA The process of transcription in eukaryotes is similar to that in prokaryotes, although there are some differences. Eukaryote genes are not grouped in operons as are prokaryote genes. Each eukaryote gene is transcribed separately, with separate transcriptional controls on each gene. Whereas prokaryotes have one type of RNA polymerase for all types of RNA, eukaryotes have a separate RNA polymerase for each type of RNA. One enzyme for mRNA-coding genes such as structural proteins. One enzyme for large rRNAs. A third enzyme for smaller rRNAs and tRNAs. Prokaryote translation begins even before transcription has finished, while eukaryotes have the two processes separated in time and location (remember the nuclear envelope). After eukaryotes transcribe an RNA, the RNA transcript is extensively modified before export to the cytoplasm. A cap of 7-methylguanine (a series of an
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: unusual base) is added to the 5' end of the mRNA; this cap is essential for binding the mRNA to the ribosome . A string of adenines (as many as 200 nucleotides known as poly-A) is added to the 3' end of the mRNA after transcription. The function of a poly-A tail is not known, but it can be used to capture mRNAs for study. Introns are cut out of the message and the exons are spliced together before the mRNA leaves the nucleus. There are several examples of identical messages being processed by different methods, often turning introns into exons and vice-versa. Protein molecules are attached to mRNAs that are exported, forming ribonucleoprotein particles (mRNPs) which may help in transport through the nuclear pores and also in attaching to ribosomes....
View Full Document

{[ snackBarMessage ]}