“Molecular Mechanism of Recombination and Crossing Over”

UNIVERSITY OF AGRICULTURAL SCIENCES, BANGALORE

DEPARTMENT OF GENETICS AND PLANT BREEDING

M.Sc. Seminar - GPB 582 (0+1)

“Molecular Mechanism of Recombination and Crossing Over”

Despite advancements in crop management and breeding, current gains in crop productivity are insufficient to meet the rising global food demand. Plant breeding fundamentally relies on reshuffling the genome to create new, superior gene combinations, by a process that occurs during meiosis through crossovers (COs). However, CO formation is limited and they occur in specific genomic regions, and is tightly regulated. Therefore, understanding and modifying the molecular control of CO patterning holds great promise for enhancing breeding efficiency and accelerating crop improvement.¹

Prophase I of meiosis is a crucial phase marked by a series of tightly regulated events that ensure proper homologous chromosome pairing and genetic recombination. During meiosis, crossover recombination ensures proper chromosome segregation, primarily through the ZMM pathway, while secondary pathways mainly repair DNA double-strand breaks. These pathways differ in sensitivity to polymorphisms, influencing how genetic variation is maintained. This is especially relevant in inbreeding plants, where reduced interhomolog polymorphism may limit recombination-based diversity.³

In order to evaluate the effect of crossing over on genetic variance (VG), about 10,000 doubled haploid lines for each of seven maize and two wheat biparental populations were simulated, both with and without crossover events during meiosis. Using genome-wide SNP marker effects and linkage maps, the VG was estimated in each scenario. The comparison between VG with crossing over and VG without crossing over allowed quantification of how much crossing over contributes to or reduces VG across various traits.²

Thus, understanding the molecular mechanisms of crossing over and recombination is crucial for unlocking how genetic diversity is generated and maintained. It helps explain how chromosomes segregate properly during meiosis, ensuring fertility and genome stability. In crop breeding, this knowledge enables more effective manipulation of recombination to combine favorable traits and improve yield. Studying these processes provides a foundation for innovative strategies in plant improvement and evolutionary research.

REFERENCES

1. Blary, A. and Jenczewski, E., 2019. Manipulation of crossover frequency and distribution for plant breeding. Theor. Appl. Genet., 132: 575–592.

2. Bernardo, R., 2025. Contribution of crossing over to genetic variance in maize and wheat populations. Plant Genome, 18(1): 20552.

3. Smith, G.R. and Nambiar, M., 2020. New solutions to old problems: molecular mechanisms of meiotic crossover control. Trends Genet., 36(5): 337–346.