---
title: "Get cytoband ideogram bands for a chromosome"
method: GET
path: "/reference/cytoband/{chrom}"
tags: ["reference"]
---

# Get cytoband ideogram bands for a chromosome

`GET /reference/cytoband/{chrom}`

## Request

- Base URL: `https://api.helena.bio` (the document declares no server; this is the origin it was published from)
- URL: `https://api.helena.bio/reference/cytoband/{chrom}`
- Auth: none declared
- TypeScript: <https://skmtc.dev/helena-bioinformatics/apis/helix-insight-variant-analysis-service/docs/reference/cytoband/:chrom/get.ts> (a function with typed inputs; its response is checked against the schema)

Return the UCSC cytoBandIdeo cytogenetic-band list for a chromosome, sorted by
    start_pos, for the SV ideogram lane.

    Accepts chr11 or 11; coordinates are returned AS PUBLISHED (UCSC 0-based half-open;
    see coord_system). arm is the None-safe leading char of band_name (p/q, or None).

    Degrade-clean: an unknown/garbage chrom, or a reference_db built before the cytoband
    asset loaded, returns 200 with bands: [] -- never a 4xx/5xx.

## Path parameters

- `chrom` string, required

## Response `200`

Successful Response

- CytobandResponse: The cytoband band list for one chromosome (the IdeogramLane read surface). bands is sorted by start_pos and is the WHOLE-chromosome list (the client draws the bar from it and scans it for the SV-midpoint containing band -- no second route). An unknown chrom or a pre-load reference_db yields bands: [] (degrade-clean), never a 4xx/5xx.
  - `chrom` string, required
  - `coord_system` string
  - `bands` CytobandBand[], required
    - `start_pos` integer, required
    - `end_pos` integer, required
    - `band_name` string, nullable
    - `gie_stain` string, nullable
    - `arm` string, nullable: Chromosome arm (p/q), the leading char of band_name; None when band_name is absent

## Other responses

- `422`: Validation Error

---

[API](https://skmtc.dev/helena-bioinformatics/apis/helix-insight-variant-analysis-service.md) - [All operations](https://skmtc.dev/helena-bioinformatics/apis/helix-insight-variant-analysis-service/llms.txt) - [OpenAPI document](https://skmtc.dev/helena-bioinformatics/apis/helix-insight-variant-analysis-service/revisions/a800b0b27feb?raw)