Post - The life span of an mRNA molecule is an important...

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

View Full Document Right Arrow Icon
Post-transcriptional mechanisms play supporting roles in the control of gene expression. Gene expression may be blocked or stimulated by any post-transcriptional step. By using regulatory mechanisms that operate after transcription, a cell can rapidly fine-tune  gene expression in response to environmental changes, without altering its transcriptional patterns. RNA processing in the nucleus and the export of mRNA to the cytoplasm provide  opportunities for gene regulation that are not available in prokaryotes. In  alternative RNA splicing , different mRNA molecules are produced from the same primary  transcript, depending on which RNA segments are treated as exons and which as introns. Regulatory proteins specific to a cell type control intron-exon choices by binding to regulatory  sequences within the primary transcript. Alternative RNA splicing significantly expands the repertoire of a set of genes.
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: The life span of an mRNA molecule is an important factor in determining the pattern of protein synthesis. Prokaryotic mRNA molecules are typically degraded after only a few minutes. Eukaryotic mRNAs typically last for hours, days, or weeks. ○ In red blood cells, mRNAs for hemoglobin polypeptides are unusually stable and are translated repeatedly. A common pathway of mRNA breakdown begins with enzymatic shortening of the poly-A tail. ○ This triggers the enzymatic removal of the 5 ′ cap. ○ The next step is rapid degradation of the mRNA by nucleases. Nucleotide sequences in the untranslated trailer region (UTR) at the 3 ′ end affect mRNA stability. ○ Transferring such a sequence from a short-lived mRNA to a normally stable mRNA results in quick mRNA degradation....
View Full Document

This note was uploaded on 01/04/2012 for the course BSC BSC1005 taught by Professor Orlando,rebecca during the Fall '10 term at Broward College.

Ask a homework question - tutors are online