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A process occurring during meiosis that results in the two kinds of gametes produced by a heterozygote not being equally common. It is more often seen in the formation of megaspores than microspores. An example is seen in maize plants that are heterozygous for a chromosome mutation, in which one of the homologues of chromosome 10 has an abnormal terminal knob. The knob acts as a centromere and causes the abnormal chromosomes to move to the poles of the spindle earlier in both the first and second divisions of meiosis. The product of meiosis is a linear tetrad in which the abnormal chromosomes are more likely to be in the outer two cells. Since all four cells of a tetrad normally develop into pollen grains, the abnormal chromosome is recovered in equal numbers among the microspores. However only the basal cell of the tetrad develops into the megaspore. Thus the abnormal chromosome is recovered at higher frequencies (about 70%) among the megaspores.
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