Answer: The parent organism whose genotype is unknown is heterozygous for purple colour with genotype Ff.
Explanation: The parent organism whose genotype is unknown has a genotype Ff. If (F) represents the allele for purple colour and it is dominant over the allele for white colour (f), a cross between (Ff) and (ff) will produce Ff, Ff, ff and ff. Two of the offsprings are heterozygous for purple colour the other two are white.
Ff x ff = Ff, Ff, ff and ff. Ff will manifest as purple colour because F is dominant over f while ff will manifest as white because f is recessive.
See the attached punnet square for further information
