Single-cell analysis detects somatic mutations. Using bulk sequencing,
somatic SNVs (e.g., the A→G mutation) and deletions (e.g., the
white space) cannot be detected because they are unique to
a cell (the yellow and red cells on the left) and,
consequently, affect only one out of many thousands of reads. SNVs cannot even
be distinguished from sequencing errors, which occur at a much higher frequency
than somatic mutations, i.e., 1/100. These low-abundant SNVs and deletions can
only be detected using single-cell sequencing, through which a heterozygous
mutation will be observed in approximately half of the reads. Both the
A→G mutation and the deletion are now easily identified. A germline
variant (e.g., the T→A SNP; purple columns) is
detectable in all single cells and in the bulk DNA. Abbreviations: SNP,
single-nucleotide polymorphism; SNV, single nucleotide variation, WGA,
whole-genome amplification.