RNA Processing in Eukaryotic Cells
RNA processing is a series of enzyme-regulated modifications that occur to the mRNA transcript in eukaryotic cells after initial transcription. This process is crucial for producing mature, functional mRNA ready for translation.
Key Steps in RNA Processing
-
Addition of Poly-A Tail (3' end)
- 100-200 Adenine nucleotides are added
- Increases stability of the mRNA
- Assists with exporting from the nucleus
-
Addition of GTP Cap (5' end)
- A modified Guanine nucleotide is added
- Protects the transcript from degradation
- Helps ribosomes attach to mRNA
-
Intron Removal
- Introns are excised during RNA processing
- Not included in the mature mRNA transcript
Definition: Introns - Sequences of an mRNA transcript that do not code for amino acids.
- Exon Retention and Splicing
- Exons are retained and connected in the mature mRNA transcript
Definition: Exons - Sequences of an mRNA transcript that do code for amino acids.
Alternative Splicing
Alternative splicing is a process where different exons are connected in various combinations to produce different mature mRNA transcripts from a single primary transcript.
Highlight: Different mRNA transcripts can be produced from one primary transcript, leading to the synthesis of different proteins.
Example: A gene with four exons 1,2,3,4 could produce multiple mRNA transcripts through alternative splicing, such as 1-2-4, 1-3-4, or 1-2-3-4, each potentially coding for a different protein.
This page provides a comprehensive guide on mRNA processing for AP students, covering essential concepts like introns ap bio definition and the importance of alternative splicing in increasing protein diversity. Understanding these processes is crucial for mastering transcription and translation in AP bio.