TABLE 5.

 Distribution of zero-, one-, and double-crossover events in mer3 mutant strains

Relevant genotypeIntervalResult at a:
30°C23°C
No. of eventsProbabilityNo. of eventsProbability
ObservedExpectedObservedExpected
0-CR1-CR2-CR0-CR1-CR2-CR0-CR1-CR2-CR0-CR1-CR2-CR
MER3CAN1-URA319128260251189714.1 × 10−1418728268247192753.7 × 10−13
URA3-CAN120628444266185651.7 × 10−1617728972241194781.1 × 10−14
mer3GDCAN1-URA330419636325163411.2 × 10−232218612347140282.1 × 10−6
URA3-CAN134118120361147302.2 × 10−335615312371126215.2 × 10−3
mer3KACAN1-URA333119520355153331.1 × 10−432715740333151345.0 × 10−1
URA3-CAN134717320364144289.7 × 10−337414012385120194.9 × 10−2
  • a Tetrads obtained in Table 2 were examined. The observed number of zero-, one- and double-crossover (0-, 1-, and 2-CR, respectively) events in an interval was derived from the number of PD, TT, and NPD events as 0-CR = PD − NPD, 1-CR = TT − 2NPD, and 2-CR = 4NPD, since only one class gives NPDs among four classes of 2-CR tetrads, assuming no chromatid interference. The expected number of 0-, 1-, and 2-CR events was predicted by a Poisson distribution from the frequency of crossing over observed in Table 2. Chi-square tests were performed to express the likelihood that the difference between the observed and expected patterns was attributable to chance.