Question

the law of segregation states that every organism possesses a pair of, or different versions of a gene, for a trait and that each parent passes a copy of only one of these to its offspring. check it

Explanation:

The Law of Segregation in genetics (a subfield of Biology, which is part of Natural Science) states that organisms have two alleles (different versions of a gene) for a trait, and each parent passes one allele to the offspring. The blank here should be filled with "alleles" as alleles are the different versions of a gene that an organism possesses in a pair for a trait.

Answer:

alleles