ALT column of VCF file contains an alternative nucleotide AND <*>

Question

Why does the ALT column of my VCF file sometimes contains an alternative nucleotide as well as a "symbolic allele" <*>? What does it mean? Image of ALT Additionally, in the INFO field, the AD tag tells me that zero reads have the symbolic allele (ie. AD=37,1,0)

Answer 1

it's a spanning deletion: https://gatk.broadinstitute.org/hc/en-us/articles/360035531912-Spanning-or-overlapping-deletions-allele-

We use the term spanning deletion or overlapping deletion to refer to a deletion that spans a position of interest.