What is the criteria of an essential ORF?
ORF disruptions that are considered essential were those that were only able to be made in the heterozygous diploid background. Additionally, dissection of tetrads from a heterozygous diploid give segregants as 2 viable : 2 dead. So, essential ORF deletions are only available as heterozygous diploids, while non essential ORF deletions are available as haploids, homozygous diploids and heterozygous diploids.
