Sequenziertiefe

Sequenziertiefe, often referred to as sequencing depth or coverage, is a fundamental metric in next-generation sequencing (NGS) that quantifies how many times each base in a reference genome or target region has been sequenced. It is typically expressed as an average number, indicating the mean number of reads that map to each position. For example, a sequencing depth of 30x means that, on average, each base in the sequenced region was covered by 30 individual sequence reads.

Higher sequencing depth generally leads to increased confidence in the accuracy of the sequenced data. This is particularly important for detecting low-frequency variants, such as somatic mutations in cancer samples or heterozygous variants in diploid organisms. With greater depth, even rare variants present in a small fraction of the DNA molecules can be reliably identified against the background noise of sequencing errors. Conversely, low sequencing depth may result in a higher chance of false negatives, where true variants are missed, or false positives, where sequencing errors are mistaken for actual biological variations.

The required sequencing depth varies depending on the specific application. Whole-genome sequencing for basic variant discovery might aim for 30-50x coverage, while targeted sequencing of specific genes or exomes might require 100x or more. Detecting rare variants or analyzing complex genomic regions often necessitates even higher depths. Factors influencing sequencing depth include the cost of reagents, the capacity of the sequencing platform, and the desired resolution for downstream analysis.