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Abstract
Selfish genetic elements are sections of DNA that get transmitted to the next generation more than expected by chance, referred to as preferential transmission. Very large haplotype based selfish genetic elements can be referred to as chromosomal drive haplotypes. Maize has at least three well characterized chromosomal drive haplotypes (Abnormal chromosome 10, K10L2, B chromosome) and ample resources making it the ideal system to study them. The maize genome is littered with large heterochromatic tandem repeats called knobs that are classified by their repeat type: knob180 and TR-1. Ab10 is a large structural variant of normal chromosome 10, with several knobs of both classes, which exhibits preferential transmission in female meiosis. Ab10 encodes two proteins, KINDR and TRKIN, which pull knobs, including those on Ab10, towards the poles of the meiotic tetrad resulting in their overrepresentation in the egg cell. K10L2 is also a structural variant of normal chromosome 10, but only encodes TRKIN and exhibits much more subtle preferential transmission than Ab10. The B chromosome exhibits preferential transmission through the male. Here we assess the structure of Abnormal chromosome 10 (Ab10) and identify a classical maize marker gene, striate leaves 2, in a previously unidentified structural variant on Ab10. Then we explored the function of TRKIN on Ab10, finding that it appears to be deleterious. Finally, we surveyed over 10,000 maize lines for Ab10, K10L2, and the B chromosome and explored their individual relationships to the genome and the abiotic environment. We found that Ab10 distribution is influenced by unlinked genetic modifiers while K10L2 and B chromosomes distribution is influenced by both genetic modifiers and the environment. The work we presented here greatly increases out understanding of selfish genetic element behavior as well as maize genome evolution.