In wheat, there is 21 chromosome pairs. Do the two chromosome of each pair carry the same genes?
Dear Gregor
The answer to your question is NO.
On the other hand, the 21 chromosome pairs of wheat (homologues chromosomes) are composed of 3 sets of homoeologous (i.e., 2 A1, 2 B1 and 2D1; 2 A2, 2 B2, 2 D2, etc.). In principle, homoeologuos chromosomes should also carry the same information, except that translocations and other chromosomal mutations can cause some differences, You can see an example in our 1987 oaper, which you can download from my ResearchGate page.
Hope this helps
Pablo
Thank you indeed for your answer. This may be answer a question of finding many SNP marker located in the same linkage group in wheat for instance (genetic map cM) and these markers assigned to different chromosomes. for instance, the linkage group 1 has 100 SNP markers. The positions of these markers were assigned to 2A1 3B1 7A2.... So, these markers might be in the same chromosome (because they are mapped together in the same linkage group) but by transactions, they assigned to different chromosome. do you agree with me
Sorry Gregor... I surely did not explain myself enough.
I am a little confused, but combining your two question ("Can markers in the same linkage group be assigned to different chromosomes?") it seems that you have a genetic map from wheat and you wish to know physical positions by looking at the Medicago map. This is absolutely wrong!!
homology/homologous. refers to the two sister copies in the diploid genome.
homoeology/homoeologous. refers to the same gene in different genomes. Due to evolutionary chromosomal mutation these genes can be in different chromosomes in the two genomes (1A-1A, 2H-2H), or one of them might have sufferend a duplication (2H-2H -> 3H-3H), etc. These two copies in the same genome are named "paralogs", and usually one of them looses its function (or it might even acquire a new one). So, you have "ortholog genes" (1A-1A 2H-2H) and "paralog genes" (1A-1A 3H-3H and 2H-2H 3H-3H).
Hexaploid wheat is an allo-hexaploid species formed by hybridization and chromosome doubling of 3 ancestors (T. urartu, the A-genome; A. squarrosa , the B-genome and one un-identified species from the Sitopsis section, the B-genome) . Broadly speaking, you should have 3 copies of the same gene that might be located into the same or different chromosomes (A, B, D); although due to function duplication some copy could be lost. Good SNPs should be specific for one of the three genomes, as it seems in your case because you get a large linkage group.
If you have 100 linked wheat snps (and the mapping was done correctly) , they surely are located into the same chromosome (lets say 1A). Looking into the Medicago genome, you can find different locations (1M to 9M); which is a very interesting evolutionary comparison, but tells you nothing about the physical location of your SNPS into chromosome 1A. Linkage groups should only differ in the relative marker distances (but not in the relative order) from chromosomes physical maps.
Hope this helps
Pablo
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