Usage of symbols
 

Dear all,

Anyone here who can tell me what this means (part of a genotype of a yeast): his3Δ1/his3Δ1 leu2Δ0/leu2Δ0

I have always been told that Δ before a gene, means that the gene is gone (knock out mutant).

But what does it mean if it stands at the end (his3Δ) or as in my other example: his3Δ1/his3Δ1 , What does that 1 mean?

I also do not get it why they put his3Δ1/his3Δ1 rather then just his3Δ1 ?

Any advice is welcome.