TABLE 4.

Analysis of crossover interference

	Meiotic products with crossover(s) present in
	Left interval (H–E) only	Right interval (E–A) only	Both	Neither	Coefficient of coincidencea	P-valueb
Control	62	76	0	164	0	<0.0001
syp-1 (RNAi)	54	24	5c	180	0.7	0.68
syp-1 (RNAi) correctedd	54	24	5	101d	0.5	0.08

^a(Number of observed meiotic products with COs in both L and R intervals)/(number expected), where expected=(frequency of COs in L interval × frequency of COs in R interval).

^bP-value from Fisher's exact test assessing the probability of obtaining the observed data set assuming independent behavior of L and R intervals.

^cFor syp-1 (RNAi), 5 of the 10 DCO products had one CO in L and one in R, 3 had two COs in L, and 2 had two COs in R. For these calculations, we specifically considered the frequency of DCO products involving both intervals.

^dFor syp-1 (RNAi) corrected, we hypothesized that the original syp-1 (RNAi) data set included meiotic products derived from two populations of meiotic tetrads: tetrads in which at least one CO had occurred (E₁ and E₂) and tetrads that lacked a CO (E₀). The number indicated in the “neither” class for the “corrected” data is an estimate of the number of NCO products derived from CO tetrads; the number of NCO products estimated to have been derived from E₀ tetrads was excluded (see materials and methods).