I am not a biologist. But need some genetic data. So I searched internet and reached NCBI's website. I came to know from the FAQ page that I can the complete genome data of organisms from ftp://ftp.ncbi.nih.gov/genomes/. So I went to the FTP site and opened the homosapien section ftp://ftp.ncbi.nih.gov/genomes/H_sapiens/. I found folders CHR_1 to CHR_22, CHR_MT,CHR_Un, CHR_X and CHR_Y.

My doubt is this : Normally there are only 23 pair chromosomes right? 1 to 22 pairs OK. XY make another pair. Then what are MT and Un ?

And the folder which I am looking is a genome of male right?


1 Answer 1


chr_MT: List of variations that map to the mitochondria

chr_Multi.txt.gz: List of variations that map to multiple chromosomes

chr_UN: List of mapped variations that are on unplaced chromosomes

see here for more information.

This is the reference genome for human, as far as I know there is no discrimination for it into male/female.

  • $\begingroup$ If it was female genome , do we have to consider X twice. $\endgroup$
    – dexterdev
    May 7, 2014 at 12:23
  • $\begingroup$ @terdon : Do you mean the AGTC sequences as 'List of variations'? $\endgroup$
    – dexterdev
    May 8, 2014 at 2:02
  • $\begingroup$ @dexterdev I did not answer this, Chris did. I just edited which is why you see my name there. I don't know what Chris meant by that since I can't find that file on the FTP site nor see it mentioned in the FTP's README (which, by the way, you should read). $\endgroup$
    – terdon
    May 8, 2014 at 2:06
  • $\begingroup$ OK @terdon I will read it. $\endgroup$
    – dexterdev
    May 8, 2014 at 2:10
  • 1
    $\begingroup$ @dexterdev "List of variations" simply means variations from the reference sequence. $\endgroup$
    – Chris
    May 8, 2014 at 7:10

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .