Repeat CT in overrepresented sequences

Question

[Analeigh]

I'm working on an scRNA-seq project and fastqc keeps identifying overrepresented sequences consisting of C and T.

CTCTCTCTCTCTCTCTCTCTCTCTCTCTCTCTCTCTCTCT

I can’t make sense on where this could come from. Any ideas? Thanks!

[GenoMax]

fastqc keeps identifying overrepresented sequences consisting of C and T.

Which read is it located in? fastqc is of limited utility with single cell data (especially 10x).

[allingt]

CT-rich regions in introns have been reported before. At what positions in your reads does it appear? How does it affect their mapping to reference?