Cause Unlocalised/Unanchored sequences in assemblies

Question

[g.yerou]

What are the primary reasons for the failure to localise/anchor sequences in genome assemblies?

[h.mon]

Please add more detail and context to your question. For example, I don't know if you are asking about:

1. why some reads can't be mapped to a reference genome, or
2. why some reads are not incorporated into a genome assembly, or
3. why some contigs / scaffolds can't be assigned to a chromosome.