In summer squash, spherical-shaped fruit has been

shown to be dominant to elongated fruit. On one
occasion two different spherical varieties were
crossed and produced all disk-shaped fruits. When
these hybrid disk-shaped fruits were crossed, they
produced 75 disk-shaped fruits, 48 spherical fruits,
and 9 elongated fruits. Explain these results. What will be an ideal response?


Answer: 9 D__ S__ disk, 3 D__ ss spherical, 3 dd S__ spherical,
1 dd ss elongated; the presence of both dominant genes produces
disk, whereas the presence of either one of the genes as
homozygous recessive produces spherical, and both recessive
produces elongated fruit.

Biology & Microbiology

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