The number of times a particular base is represented within all the reads from sequencing. The higher the read depth, the more confidence scientists can have in identifying a base – known as ‘base calling’.
Use in clinical context
Sequencing is not a fault-proof process and sometimes the wrong base can be incorporated into the DNA fragment. By sequencing each fragment numerous times to produce multiple reads, scientists can be more confident that any variants identified are true variants and not artefacts from the sequencing process. The number of times each individual base has been sequenced i.e. the number of reads it appears in is referred to as the read depth, and the greater the depth, the more confident scientists can be that the variant is real.