This tool uses the maize Recombination Nodule map (Anderson et al. 2003 and 2004) to calculate approximate chromosomal positions for loci given a genetic map.

To run the calculator on your own machine, visit the download page).

Step 1: Select a chromosome:

Step 2: Select a map to use...
... or paste your map into the following space. What type of map is it?
You may want to put in a conversion factor for cytological map translations:
Also, see this important note about adding your own map.

How To Submit Your Own Map Data:
Your map data MUST include the following:

  1. Your map must consist of a number of lines. Each line should start with the name of the locus, followed by a tab, followed by the centiMorgan value for that locus.
  2. The program assumes that the tip of the short arm is at 0.0 cM UNLESS you submit a locus with a cM value of less than zero.
  3. The program also assumes that the tip of the long arm is at the cM value of your highest submitted cM value. So, if you believe that the tip is not exactly at this locus, you should add a tip1 locus at the end with the cM value of where you believe the tip to be.
  4. There must be ONE locus beginning with the characters "cent". The program will assume that this is the centromere.

Here is a sample set to use while experimenting. Assume that this set is for chromosome #1.

tub1	11.0
umc157(chn)	29.8
umc76	48.4
asg45(ptk)	74.0
csu3	88.5
umc67a	112.9
cent1	123.0
asg62	142.8
umc128	168.1
cdj2	180.7
umc107a(croc)	199.2
umc161a	219.3
bnl6.32	245.2

... and here is a cytogenetic sample for chromosome #9:

umc109 (CBM 9.01)	0.79
bz1 (CBM 9.02)	0.65
wx1 (CBM 9.03)	0.13
cent	0.0
rgpr3235a	0.04
csu54b (CBM 9.08)	0.95

Note About the Genetic Map Dataset: Centromeres have artificially been added to this map based on recombination data from Ed Coe.

Note About Conversion Factor: Entering a number in this box causes the resulting genetic map to be amplified by that factor in order to aid in matching the output to other genetic maps you may have.

Comments or questions? Send an email to Carolyn Lawrence at