Learning objectives
By the end of this lesson you should be able to identify the parts of a FASTQ record and distinguish a nucleotide sequence from its associated quality scores.
FASTQ record structure
@read_001 ACGTACGT + IIIIIIII
Line 1 is the read identifier, line 2 contains the nucleotide sequence, line 3 is the separator, and line 4 contains quality characters. In the commonly used Phred+33 format, the character I represents a Phred quality score of 40.
Short exercise
Count the bases in this read. Check whether the number of quality characters is equal to the number of nucleotides.
Next step: Explore the example video about quality control, then complete the practice project.