For decades, vast stretches of the animal genome were dismissed as genetic “junk”—repetitive DNA sequences that do not encode proteins and appeared to have no clear biological purpose. A new study from ETH Zurich now challenges that view with evidence that these sequences may act as molecular identification tags during meiosis, the specialized cell division that produces sperm and egg cells. In female fruit flies, researchers found that repeating DNA sequences known as satellite DNA help matching chromosome pairs recognize one another, while a glue-like protein called D1 physically links the correct partners. The discovery offers a striking explanation for how chromosomes avoid pairing with the wrong partners and raises the possibility that rapidly evolving repetitive DNA could contribute to the emergence of new species.
Most cells in humans and other animals carry two copies of each chromosome, one inherited from the mother and one from the father. Before sexual reproduction can occur, this duplicated genetic package must be reduced by half. Meiosis accomplishes that task by producing cells containing a single chromosome set. During fertilization, two such cells fuse, restoring the normal chromosome number. The process is highly sensitive: if chromosomes are distributed unevenly, the resulting reproductive cells can carry missing or extra chromosomes, often causing infertility or developmental abnormalities. For meiosis to work correctly, the maternal and paternal versions of each chromosome must first locate one another inside the crowded cell nucleus and pair up.
That search is not straightforward. A nucleus contains a dense mixture of chromosomes, proteins and regulatory molecules, all occupying a confined three-dimensional space. Matching chromosomes must distinguish themselves from other chromosomes that may be similar in size or shape, while avoiding temporary contacts that could lead to incorrect alignment. Researchers have long understood that chromosome pairing involves physical interactions and molecular signals, but the mechanism that enables one chromosome to identify its true partner has remained incompletely explained. The ETH Zurich team, led by biochemist Madhav Jagannathan and doctoral researcher Lena Skrutl, investigated this problem in the egg cells of the fruit fly Drosophila melanogaster, a model organism widely used to study genetics and cell biology.
Their focus was satellite DNA, a class of repetitive sequence found in large blocks within animal genomes. Satellite DNA is typically composed of short DNA motifs repeated thousands or even millions of times, often in regions surrounding the centromeres or at other structurally important parts of chromosomes. Because these sequences do not provide instructions for making proteins, they were historically treated as genomic clutter. Earlier experiments had shown that removing satellite DNA from a single chromosome did not prevent chromosome pairing. That result appeared to suggest that satellite repeats were dispensable. The new work indicates that the interpretation was incomplete: removing one barcode does not eliminate the overall matching system because the remaining chromosomes can still pair normally, leaving the altered pair as the final unmatched combination.
To test the idea more rigorously, the researchers disrupted the satellite DNA patterns on two different chromosomes. This created two chromosome pairs with damaged or missing recognition signatures. Under those conditions, the pairing process became unreliable. Chromosomes frequently associated with incorrect partners, demonstrating that the satellite sequences were not merely passive structural material. Instead, each chromosome pair appeared to carry a distinctive repetitive pattern that could function like a molecular barcode. When all barcodes are intact, matching chromosomes can locate one another efficiently. When two recognition systems are disrupted simultaneously, the cell loses enough information to make reliable partner selections, and incorrect pairings become more common.
The study also identified the molecular component that converts recognition into a stable physical connection. The protein D1 binds satellite DNA and acts as a kind of adhesive between corresponding chromosome regions. In this model, satellite repeats provide the identity signal, while D1 helps hold chromosomes together once compatible patterns are encountered. The process resembles a molecular matching system rather than a simple lock-and-key interaction. D1 must recognize the appropriate repetitive DNA landscape and establish a connection strong enough to stabilize the paired chromosomes during the early stages of meiosis. This partnership between repetitive DNA and a binding protein gives the sequences a direct functional role in reproductive cell formation.
The researchers found that the system can also become vulnerable when satellite DNA patterns are altered. A deletion or naturally occurring mutation that changes part of a chromosome’s recognition pattern may cause D1 to bind chromosomes that do not truly belong together. In such cases, the adhesive protein may still function, but it is working from faulty information. The resulting mispairing can interfere with the orderly movement of chromosomes during meiosis and may produce reproductive cells with abnormal chromosome complements. The findings therefore connect small changes in repetitive DNA to potentially major consequences for fertility and genome stability, at least in the fruit fly system examined in the study.
The discovery could also help explain why satellite DNA evolves so rapidly and why populations that become geographically isolated can eventually split into separate species. Within a freely interbreeding population, chromosome recognition patterns are continually mixed through reproduction, helping maintain compatibility. But when a population is divided by a physical barrier—such as a mountain range, changing climate or the separation of habitats—its satellite DNA can evolve independently. Over many generations, the repetitive sequences in the two groups may diverge sufficiently that chromosomes from the different populations no longer recognize one another correctly during meiosis. Even if the animals can mate, their hybrid offspring may produce defective reproductive cells, creating a genetic barrier between the populations.
This possibility is consistent with observations involving Drosophila melanogaster and its close relative Drosophila simulans, which diverged approximately two to three million years ago. Hybrids between the species can experience severe chromosome-pairing problems during meiosis, and differences in repetitive DNA are among the factors that may contribute to this incompatibility. The ETH Zurich researchers emphasize that their results do not yet demonstrate that the same barcode mechanism operates in humans or other animals. Human genomes also contain abundant satellite DNA, particularly in centromeric and pericentromeric regions, but whether human chromosome pairs use comparable recognition patterns and molecular adhesives remains an open question. Nevertheless, the fruit fly results provide a framework for investigating repetitive DNA as an active participant in chromosome behavior rather than as biological residue.
The study, published in Nature Communications, transforms the familiar concept of “junk DNA” into something far more dynamic: a rapidly changing molecular identity system that can guide one of the most consequential events in sexual reproduction. By showing that satellite DNA patterns help chromosomes find the correct partners and that D1 can secure those matches, the researchers have linked repetitive genomic sequences to the accuracy of meiosis, fertility and possibly the formation of new species. The work also highlights how much biological information may be hidden in parts of the genome once considered unimportant. What looks repetitive and meaningless at the sequence level may, in the living cell, function as a precise address label—one that tells chromosomes where they belong and with whom they must unite.
Subject of Research: The role of satellite DNA repeats and the D1 protein in chromosome pairing during meiosis in fruit flies.
Article Title: Meiotic pairing through barcode-like satellite DNA repeats
News Publication Date: 16 June 2026
Web References: Nature Communications article; DOI: 10.1038/s41467-026-74398-x
References: Skrutl L. et al., “Meiotic pairing through barcode-like satellite DNA repeats,” Nature Communications, published 16 June 2026.
Image Credits: Image from Skrutl L. et al., Nature Communications 17, 2026.
Keywords: satellite DNA, meiosis, chromosome pairing, D1 protein, junk DNA, repetitive DNA, Drosophila melanogaster, fertility, speciation, genome evolution, chromosome recognition
Tags: chromosome pairing accuracy and avoiding errorsChromosome pairing during meiosischromosome segregation and reproductive stabilitycontribution of repetitive DNA to speciationevolutionary significance of repetitive DNAgenetic “junk” DNA and its biological functionmechanisms of chromosome recognitionmeiosis and gamete formationmolecular identification tags in meiosisrepetitive DNA sequences in genomerole of D1 protein in chromosome linkagesatellite DNA in chromosome recognition
