I have exome data for a few sets of parent-offspring trios, in which offspring have phenotypically related but probably genetically different diseases. Their parents are unaffected so I am particularly interested in identifying de novo mutations. My plan was to analyse each individual separately up to the variant calling phase and then to input three (mother, father, child) analysis-ready BAMs into the UnifiedGenotyper along with a ped file. My questions are:
1) Can you tell me whether the UnifiedGenotyper uses pedigree information in the ped file to call genotypes more accurately? In other words, is this better than calling variants jointly without supplying the ped file? If not, does GATK recommend any external tools for doing this step?
2) It is better to call variants jointly using all the trios (even though they are not related and probably don't share the same disease-causing mutations)?
Is it possible to use PhaseByTransmission with families that are larger than a single trio? I have a family with four siblings. If I include all of the siblings in the PED I get:
PhaseByTransmission - Caution: Family BMD has 6 members; At the moment Phase By Transmission only supports trios and parent/child pairs. Family skipped. ERROR MESSAGE: Bad input: No PED file passed or no trios found in PED file. Aborted.
And if I just include the one key trio with the proband, I get the following:
ERROR MESSAGE: Sample BMD006_R found in data sources but not in pedigree files with STRICT pedigree validation
There does not seem to be an accessible argument for relaxing the pedigree validation. Is there a way to use PhaseByTransmission with my larger family?