Apart from considering education and income levels, individuals tend to choose partner with similar DNA, according to a University of Colorado-Boulder study.

Researchers said that couples are genetically similar to their spouses than they are to random individuals from the same population.

Previous studies showed that people are more likely to choose individuals with similar characteristics, like religion, age, race, income, body type and education level, as mates. Among these factors, education is the most preferred and the phenomenon is called educational assortative mating.

"It's well known that people marry folks who are like them," said Benjamin Domingue, lead author of the paper and a research associate at CU-Boulder's Institute of Behavioral Science, according to a news release. "But there's been a question about whether we mate at random with respect to genetics."

"Genes drive so many things that can structure opportunities and outcomes that determine who we mate with," Domingue said, webmd reports.

For the study, researchers used genomic data collected by the Health and Retirement Study. They analysed the genome of 825 non-Hispanic white American couples and focused on Single-Nucleotide Polymorphisms. SNPs are common points in DNA that differ among individuals.

The researchers observed fewer differences in the DNA between married people than between two randomly selected individuals. They also found that the inclination to choose a genetically similar spouse, known as genetic assortative mating, constitutes a third of the strength of educational assortative mating. In other words, DNA matching also plays a vital role in mate selection.

The finding is published in the journal Proceedings of the National Academy of Sciences.