If it were not for the formation of the chiasmata during prophase I, it would be proper to call the first meiotic division, reductional and the second meiotic division equational. However, the chiasmata represent actual exchanges of segments between two nonsister chromatids of maternal and paternal origin. Any one chiasma involves an exchange between only two of the four chromatids in the tetrad. Therefore,... if a single chiasma were formed in prophase I, anaphase I would produce chromosomes of exclusively maternal or paternal origin up to the point of exchange. Therefore, this region of the chromosome is both cytologically and genetically haploid, and meiosis I is reductional for this region of the chromosome pair. However, beyond the point of exchange each chromosome in anaphase I carries chromatid segments of both maternal and paternal origin, and is thus still genetically diploid. Reduction to a truly haploid condition for this region is complete only after the second meiotic division. Only then does each chromatid consist of a strand of single origin throughout its length. A single chromatid (now a daughter chromosome) may, of course, contain segments of both maternal and paternal origin, but at any given position or locus on the chromosome only one kind of gene or allele will be present. Thus, each meiotic division is both reductional and equational for different regions of the chromosomes, depending on the number and placement of the chiasmata. 
(DAVID J. MERRELL, An Introduction to Genetics, W. W. Norton & Co., Inc., New York)