- Genotyping arrays are laboratory tools used to identify genetic variants at thousands or millions of selected positions across an animal’s genome. They commonly detect single-nucleotide polymorphisms (SNPs) and, depending on the array design, may also assess selected insertions, deletions, or other genomic variants. In animal breeding, genotyping arrays provide a practical way to study genetic variation, estimate relationships among animals, identify inherited characteristics, and support more accurate genetic evaluation.
- A genotyping array contains many DNA probes designed to recognize specific genomic sequences. DNA extracted from an animal’s sample is processed and applied to the array, where matching sequences generate detectable signals. The resulting data indicate which alleles are present at the targeted positions. These allele combinations are called genotypes and can be used to compare animals, investigate genetic diversity, and estimate the inheritance of genomic regions. Blood, hair roots, ear tissue, semen, and other suitable biological samples may be used, depending on the species and laboratory protocol.
- Most genotyping arrays used in livestock research focus on SNPs because these variants are widespread throughout the genome and can be measured efficiently. Different arrays are designed for particular species, breeds, research purposes, and levels of genomic coverage. For example, cattle, sheep, goats, pigs, and poultry may have species-specific arrays containing markers selected for genetic evaluation, parentage verification, disease research, or genomic selection. High-density arrays test more genomic positions than low-density arrays, while low-density arrays can reduce costs when fewer markers are sufficient or when imputation is used.
- One of the most important applications of genotyping arrays is genomic selection. In this approach, marker information from many regions of the genome is combined with phenotypic records and reference-population data to estimate an animal’s genomic estimated breeding value (GEBV). Breeders can use these estimates to select breeding males and females for traits such as milk production, growth rate, feed efficiency, fertility, carcass quality, disease resistance, and longevity. Genotyping young animals can support selection decisions before they have produced offspring or expressed traits that require time to measure.
- Genotyping arrays also support genetic relationship estimation and inbreeding management. SNP data can be used to estimate genomic relationships between animals, identify individuals with high levels of genomic similarity, and help breeders avoid matings that could increase inbreeding. Depending on marker coverage and analytical methods, array data can also help identify runs of homozygosity (ROH), which are continuous genomic regions where an animal carries two copies of the same allele. These analyses contribute to monitoring genetic diversity and managing the long-term health of breeding populations.
- Another application is parentage verification and pedigree validation. Genotypes from offspring and their possible parents can be compared to determine whether the observed inheritance patterns are compatible with a proposed pedigree. Arrays may also help identify sample mix-ups and investigate genetic relationships within breeding populations. Their reliability depends on marker quality, correct sample identification, and appropriate analysis.
- Genotyping arrays are valuable in research on genetic mapping, quantitative trait loci (QTL), and genome-wide association studies (GWAS). By examining differences in marker genotypes among animals with different trait measurements, researchers can identify genomic regions statistically associated with traits of interest. These associations can help locate regions involved in production, reproduction, health, and adaptation. However, an associated marker is not necessarily the causal variant itself; further research may be needed to identify the biological mechanism responsible for a trait.
- Array data can also contribute to genetic diversity assessment, breed characterization, and conservation programs. Comparing allele frequencies and genomic relationships among breeds helps researchers study population structure, distinguish genetic lineages, and monitor diversity over time. This information can be particularly useful for small or locally adapted breeds that may carry valuable traits related to disease resistance, climate adaptation, or survival under challenging conditions.
- The usefulness of a genotyping array depends on several factors, including marker density, the distribution of markers across the genome, DNA sample quality, genotype-calling accuracy, and the suitability of the array for the population being studied. An array developed using one breed may perform less effectively in another if relevant genetic variants are poorly represented or if the relationships between markers and causal variants differ. Linkage disequilibrium, which describes the non-random association of alleles at different genomic positions, is especially important because genomic prediction often relies on marker relationships with trait-influencing variants.
- Although genotyping arrays are efficient and generally less expensive per animal than whole-genome sequencing, they examine predefined genomic positions rather than every DNA base. As a result, they may miss rare variants, previously unknown mutations, and structural changes that are not specifically represented on the array. Imputation can be used to infer unobserved genotypes from observed markers, but accuracy depends on the reference population, marker density, breed composition, and genomic relationships among animals. Whole-genome sequencing may be more appropriate when comprehensive variant discovery is required.
- In practical breeding programs, genotyping arrays are most effective when integrated with reliable phenotypic records, pedigree information, well-designed reference populations, and appropriate statistical models. The cost of testing, the accuracy of genomic predictions, and the expected value of earlier or more precise selection should be considered when deciding which animals to genotype. Breeders must also protect genetic diversity and avoid excessive reliance on a small number of genetically superior animals, which can increase inbreeding and reduce future selection opportunities.
- Overall, genotyping arrays have become important tools in modern animal breeding because they provide genome-wide marker information efficiently and consistently. Their applications range from parentage verification and genetic diversity monitoring to genomic selection and genetic research. When combined with sound quantitative genetics and responsible breeding objectives, genotyping arrays help improve the accuracy of genetic evaluation and support sustainable livestock improvement. Related concepts include SNP genotyping, genetic markers, genomic selection, genomic estimated breeding values, linkage disequilibrium, genetic mapping, genetic diversity, and whole-genome sequencing.
