> ## 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. # GC Content > Enforce GC content within specified range
GC Content

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Source
evo-design/proto-language/proto\_language/constraint/sequence\_composition/gc\_content\_constraint.py
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Constraint contributors
Enforce GC content within specified range. This constraint function calculates the percentage of guanine (G) and cytosine (C) nucleotides in DNA or RNA sequences and evaluates whether it falls within a specified acceptable range. GC content is a fundamental sequence property that affects DNA stability, melting temperature, gene expression patterns, and technical considerations like PCR amplification efficiency. ## API Reference
ConfigGCContentConfig Source
Configuration for GC content constraint. This class defines configuration parameters for evaluating the GC content in DNA or RNA sequences. This penalty scales linearly with deviation from the acceptable range. Minimum acceptable GC content percentage (0-100) Maximum acceptable GC content percentage (0-100)
ReturnsConstraintOutput
One result per sequence. A score of 0.0 indicates GC content is within the acceptable range \[min\_gc, max\_gc]. Higher scores indicate greater deviation from the acceptable range, with penalties scaling linearly with the deviation distance. The `metadata` field carries `gc_content`.
## Usage Evaluating GC content constraint: ```python python icon="python" theme={null} >>> seq = Sequence("ATCGATCG", "dna") >>> cfg = GCContentConfig(min_gc=40.0, max_gc=60.0) >>> result = gc_content_constraint([(seq,)], config=cfg) >>> print(result[0].score) # 0.0 (50% GC content is within acceptable range) ``` ## Metadata | Property | Value | | --------------- | ----------------------- | | Key | `gc-content` | | Function | `gc_content_constraint` | | Category | `sequence_composition` | | Mode | `discrete` | | Uses GPU | `False` | | Supported Types | `dna`, `rna` |