Wild-type Arabidopsis has 5 chromosomes (2n = 10). Trisomic plants are designated as "Tr" followed by the trisomic chromosome number-that is, Tr1 is trisomic for chromosome 1. Assuming that trisomy is fully viable and that all possible pairing configurations (including nonpairing) are possible at meiosis, what proportion of the progeny from the cross wt × Tr1 will have a wild-type chromosomal complement?

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Quizplus · Accepted Answer

In the cross wt (2n = 10) × Tr1 (2n + 1 = 11), the Tr1 parent can produce gametes with either 5 or 6 chromosomes. Only the gametes with 5 chromosomes will result in wild-type progeny when combined with the normal gametes from the wt parent. The probability of the Tr1 parent producing a gamete with 5 chromosomes is 1/3, as there are three possible segregation patterns (5:6, 6:5, and 5:5) during meiosis, but only one results in a 5-chromosome gamete.

Wild-Type Arabidopsis Has 5 Chromosomes (2n = 10)