In the plant genus Triticum there are many different polyploid species, as well as
diploid species. Crosses were made between three different species, and hybrids
were obtained. The meiotic pairing was observed in each hybrid, and this is recorded
in the following table. (A bivalent is two homologous chromosomes paired at
meiosis, and a univalent is an unpaired chromosome at meiosis.)
Species crossed to make hybrid
Pairing in hybrid
1. T. turdigum × T. monococcum 7 bivalents + 7 univalents
2. T. aestivum × T. monococcum 7 bivalents + 14 univalents
3. T. aestivum × T. turdigum 14 bivalents + 7 univalents
Explain these results and, in doing so,
a) deduce the somatic chromosome number of each species used.
b) state which species are polyploid and whether they are autopolyploids or allopolyploids.
c) account for the chromosome pairing pattern in the three hybrids.
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