unsigned int offset
offset of this record from the previous one, in bases
unsigned char mapQuality
root mean squared maximum mapping quality for overlapping reads
unsigned depth
log10 minimum likelihood * 10 and the number of mapped reads
unsigned char lk[10]
log10 likelihood ratio * 10 for genotypes AA, AC, AG, AT, CC, CG, CT, GG, GT, TT
unsigned char refBase
"XACMGRSVTWYHKDBN"[ref_base] gives the reference base