Practice question

Ordered tetrads in Neurospora permit centromere mapping because spindle geometry preserved along narrow ascus axis. Locus close to centromere shows mostly FDS patterns due rare exchange in proximal interval, distal locus shows frequent SDS due to exchange between centromere and gene. Counting proportion asci displaying SDS among total asci measures gene-centromere recombination frequency directly, independent another gene marker. Formula distance = half percent SDS converts to centimorgans. This unique advantage allows positioning centromere as if it were genetic locus dividing at meiosis I, enabling chromosome maps anchored to centromere.