Answer:
The cross is as follows:
P: D/d × d/d
Step-by-step explanation:
Half of the F1 progeny are mutant. The mutation results in 3 cotyledons is dominant and the original mutant is heterozygous.
If D denotes the mutant allele and d denotes the wild type allele.
The cross is as follows:
P: D/d × d/d
F1 denotes D/d three cotyledons
d/d denote two cotyledons