Comparative Genomic Hybridization

Infer relative genomic copy-number gains and losses by competitively hybridizing differently labeled test and reference DNA and mapping their normalized signal ratio by locus.

Version

v1 · 2026-08-30 · History

Domain-specific #

1512

Origin domain

cytogenetics

Subdomain

genome-wide copy-number analysis

Aliases

CGH, Chromosomal CGH, Comparative genome hybridization

Core Idea

Comparative genomic hybridization (CGH) is a molecular-cytogenetic measurement architecture for detecting relative DNA copy-number gains and losses across a genome. Genomic DNA from a test sample and a reference sample is labeled with distinguishable fluorophores, mixed, and competitively hybridized to a common locus-ordered substrate. The normalized test-to-reference signal ratio is mapped by genomic position; departures from the balanced ratio indicate relative dosage differences.

Conventional CGH uses normal metaphase chromosomes as the substrate. Array CGH replaces chromosomes with mapped DNA probes, raising and regularizing resolution while retaining the same comparative-ratio principle.

Scope of Application

CGH recurs in cancer cytogenetics, tumor evolution, constitutional copy-number analysis, developmental-disorder investigation, prenatal or postnatal diagnostics, model-organism genomics, and research screening for deletions and amplifications.

Conventional chromosomal CGH and array CGH are variants of the same abstraction. Their substrates, resolution, dynamic range, DNA requirements, and processing differ, but each compares two genomic samples by competitive hybridization and spatial signal ratio.

Clinical use requires validated platforms, quality controls, reference populations, interpretation standards, and confirmatory or orthogonal tests where appropriate. This node describes the measurement architecture, not a stand-alone medical recommendation.

Clarity

Recognition begins with two genomic DNA inputs and different labels. If a single sample is hybridized without a comparative reference signal, the assay is not CGH in this exact sense. Both samples must address the same ordered loci under comparable conditions.

For locus \(i\), a common summary is

Manages Complexity

CGH converts millions or billions of genomic bases into a spatial dosage profile. Instead of selecting one suspected locus at a time, it surveys the genome and routes anomalous regions to focused interpretation.

Competitive co-hybridization controls many environmental variables because test and reference experience the same substrate and reaction. Taking their ratio cancels shared multiplicative effects more effectively than comparing unrelated absolute signals.

Abstract Reasoning

Let true hybridizable copy amounts at locus \(i\) be \(C_{T,i}\) and \(C_{R,i}\). A simplified model is

\[ I_{T,i}=a_T h_i C_{T,i}+\epsilon_{T,i},\qquad I_{R,i}=a_R h_i C_{R,i}+\epsilon_{R,i}, \]

where \(h_i\) represents locus-specific hybridization efficiency and \(a_T,a_R\) label/channel effects. After normalization, the ratio reduces the shared \(h_i\) and estimates \(C_{T,i}/C_{R,i}\).

Knowledge Transfer

Literal transfer holds across chromosomal and array platforms because test/reference competition and locus-resolved ratio remain invariant. Cancer, prenatal, and constitutional contexts change samples and interpretation, not the comparator architecture.

The portable residue is ratio-based comparative measurement: expose target and reference to shared conditions and infer relative quantity from their signal quotient. Live prime:ratio supplies this core. CGH adds genomic DNA, hybridization, fluorophores, ordered loci, copy-number biology, and cytogenetic limitations.

Relationships to Other Abstractions

Current abstraction Comparative Genomic Hybridization Domain-specific

Parents (1) — more general patterns this builds on

• Comparative Genomic Hybridization presupposes Ratio Prime

  The minimal prospective placement is a strict composition/presupposes edge to live prime:ratio.

Hierarchy path (1) — routes to 1 parentless root

• Comparative Genomic Hybridization → Ratio → Comparison → Self Checking

Neighborhood in Abstraction Space

Comparative Genomic Hybridization sits in a sparse region of the domain-specific corpus (89^th percentile for distinctiveness): few abstractions share its structure, so a faithful description tends to retrieve it precisely.

Family — Genomic Mapping & Sequence Assays (6 abstractions)

Nearest neighbors

• Radiation Hybrid Mapping — 0.85
• Fluorescence In Situ Hybridization — 0.79
• Surveyor Nuclease Assay — 0.78
• Epitope mapping — 0.78
• DNA Replication — 0.78

Computed from structural-signature embeddings · 2026-09-08