---
title: "Alternative Splicing and One Gene, Many Proteins"
description: "The spliceosome can include or skip particular exons, so one gene yields several related proteins depending on cell type and conditions. Which sites are used is set by regulatory proteins binding near"
canonical: https://lightmysky.com/learn/science/alternative-splicing-and-one-gene-many-proteins-mt_xei9v3IIsE
source: https://lightmysky.com/learn/science/alternative-splicing-and-one-gene-many-proteins-mt_xei9v3IIsE.md
retrieved: 2026-09-12
---

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# Alternative Splicing and One Gene, Many Proteins

The spliceosome can include or skip particular exons, so one gene yields several related proteins depending on cell type and conditions. Which sites are used is set by regulatory proteins binding near them.

Subject: Science · Area: Biochemistry & Molecular Biology · Ages 20 to 21
Page: https://lightmysky.com/learn/science/alternative-splicing-and-one-gene-many-proteins-mt_xei9v3IIsE

## Ready when they can

- Works out the possible mature transcripts from a stated exon arrangement.
- Explains what decides which splice sites are used in a given cell.
- Links a mutation at a splice site to a protein change without calling it a coding change.

## Lesson: One gene, many proteins

Your genes are split: coding exons interrupted by noncoding introns. The spliceosome cuts every intron at short consensus marks, a 5 prime site plus a branch point plus a 3 prime site, and joins the exons with two rounds of chemistry. A single shifted cut can drop an exon or break the reading frame, so site choice is exact.

**Example.** Alternative splicing reuses that machinery selectively. Some cassettes are skipped, some introns kept, and some cut sites shifted, so one starting transcript yields a family of related proteins. To count the options, combine the cassettes: each cassette doubles the set, so three cassettes give two times two times two, which is eight possible transcripts.

Which sites win depends on the cell. SR proteins usually promote a nearby site while hnRNP proteins suppress it, and their levels differ between tissues, with RNA shape and polymerase speed adding votes. A mutation at a splice site reroutes this choice without touching any codon, forcing skipped exons or rogue ones, so the protein changes even though no codon was directly altered.

**Tip.** To work any splicing question, list the cassettes, decide which sites the regulators favor, and build the exon set before judging the protein.

**Recap.** One transcript can be cut many ways, and regulator levels in each cell choose the way.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Enhancers, Accessibility and Combinatorial Control](https://lightmysky.com/learn/science/enhancers-accessibility-and-combinatorial-control-mt_BTMCj6V6jD)
- [Transcription and RNA Splicing in Eukaryotes](https://lightmysky.com/learn/science/transcription-and-rna-splicing-in-eukaryotes-mt_j2vc70vH5t)

## Opens up

- [Small RNAs and Silencing After Transcription](https://lightmysky.com/learn/science/small-rnas-and-silencing-after-transcription-mt_1AozDyS1Mn)