In trans configuration, parental gametes are
Trans configuration also termed repulsion places dominant allele of one locus and recessive allele of second locus on same homolog, genotype written Ab / aB. During meiosis without crossing over between loci, these chromosomes segregate intact, so gametes carrying Ab and aB constitute parental nonrecombinant class observed at high frequency. Recombinant class AB and ab appears only after single crossover exchanges segments. Cis configuration AB/ab reverses parental identities but does not alter physical distance, therefore recombination frequency remains governed by interval length and chromat
Ref: Griffiths et al., Introduction to Genetic Analysis, 12th ed., Chapter 4: Cis-Trans Configurations and Gamete Types