Practice question

Ordered tetrads preserve meiosis I versus meiosis II segregation information through linear spore arrangement that reflects spindle orientation during both divisions. This allows distinction first division segregation without gene-centromere crossover versus second division segregation with crossover between gene and centromere. Counting SDS asci yields direct estimate recombination between any single gene and its centromere using half SDS frequency formula. Unordered tetrads lack spatial order so FDS and SDS indistinguishable, precluding centromere mapping entirely. Therefore ordered system uniquely allows centromere localization relative to genes, positioning centromere as genetic landmark.