> ## Documentation Index > Fetch the complete documentation index at: https://proto.evodesign.org/docs/llms.txt > Use this file to discover all available pages before exploring further. # Random Nucleotide Mutation > Random nucleotide mutations using IUPAC substitution schemes

**License:** Random Nucleotide Sampling is open source and free for academic and commercial use under an MIT license. Please refer to [the license](https://github.com/evo-design/proto-tools) for full terms.

This generator is open source. Any third-party models, product names, or trademarks referenced are the property of their respective owners, and Proto is not affiliated with them.

Tools Used Tools Used Source Source

Go to Tool Page

evo-design/proto-language/proto\_language/generator/random\_nucleotide\_generator.py

View source

Generator contributors

Nucleotide sequence generator that introduces random mutations. This generator creates sequence diversity by randomly mutating masked positions in DNA or RNA sequences. Nucleotide selection is controlled by the IUPAC substitution scheme, allowing targeted mutation strategies (e.g., transitions only with `"R"`/`"Y"`, or any base with `"N"`). The generator category is `"mutation"`. When the assigned segment has a starting sequence (or an upstream optimizer stage has populated proposals), `masking_strategy` controls which positions are mutated on each call. When the segment has no starting sequence, the first `sample()` call fills each proposal with a fully random sequence of the segment's length using the configured `substitution_scheme`; subsequent calls then apply `masking_strategy` normally. ## API Reference

ConfigRandomNucleotideGeneratorConfig Source

Configuration object for RandomNucleotideGenerator. This class defines configuration parameters for the random nucleotide generator, which introduces random nucleotide mutations at masked positions using IUPAC ambiguity code-based sampling. Controls which positions to mask for sampling. Default: random 30%. IUPAC code defining the nucleotide substitution pool. Options: `N`, `R`, `Y`, `S`, `W`, `K`, `M`, `B`, `D`, `H`, `V`

## Usage ```python python icon="python" theme={null} >>> from proto_language.generator import RandomNucleotideGenerator, RandomNucleotideGeneratorConfig >>> from proto_language.core import Segment >>> config = RandomNucleotideGeneratorConfig( ... masking_strategy=MaskingStrategy(num_mutations=2), ... ) >>> gen = RandomNucleotideGenerator(config) >>> segment = Segment(length=100, sequence_type="dna") >>> gen.assign(segment) >>> gen.sample() # First call: random init (no starting sequence) >>> gen.sample() # Second call onward: 2 random nucleotide mutations ``` ## Metadata | Property | Value | | ------------------------ | --------------------------- | | Key | `random-nucleotide` | | Class | `RandomNucleotideGenerator` | | Category | `mutation` | | Input Type | `starting_sequence` | | Uses GPU | `False` | | Supported Sequence Types | `dna`, `rna` | | Allows Empty Start | `True` |