Unkown NCBI genome chromosomes

Question

[robbenstijn]

Hi everyone,

I am trying to work with the GRCh38 (https://www-ncbi-nlm-nih-gov.tudelft.idm.oclc.org/genome/guide/human/#learn) from ncbi but i am encountering all sorts of chromosomes with which I am not familiar. Some examples to illustrate:

chr11_KI270721v1_random chr19_KV575247v1_alt chr22_KQ759762v1_fix

It is probably a rookie question but does anyone know what they mean? I can't find anything on the ncbi website.

Any help is much appreciated!

Stijn

[GenoMax]

They are valid parts of human genome. Take a look at Heng Li's blog post.

Answer 1

[vkkodali_ncbi]

For definitions of these terms, see: https://www.ncbi.nlm.nih.gov/grc/help/definitions/

• chr11_KI270721v1_random -- unlocalized scaffold
• chrUn_GL000195v1 -- unplaced scaffold
• chr19_KV575247v1_alt -- alternate locus or a novel-patch sequence
• chr22_KQ759762v1_fix -- fix-patch sequence