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With nonalternate segregation (neighboring or
adjacent chromosomes), the two chromosomes
on the left go into one gamete and the two chromosomes
on the right into the other (adjacent-
2). With the other possibility, the upper chromosomes
go into one gamete, and the lower
two into the other (adjacent-1). In each of the
last two cases, an unbalanced distribution of
the involved chromosome segments results. For
example, after adjacent-2 segregation, gametes
receive a partial duplication of the chromosome
segment marked with red and a partial deficiency
of the segment marked with blue (left
pair of chromosomes) or a partial duplication of
the blue segment and a partial deficiency of the
red (duplication/deficiency). Different types of
disorders result depending on the chromosome
segments involved.