There are four pairs of linked genes in Syrians known at this time. The X-Linked Yellow; Banded & Hair Length; C-locus & Cinnamon; Umbrous & Satin. For information on Yellow inheritance go to X-Linked below. The other 3 linked sets can recombine but with varying degrees of success.
Let's begin with Banded and Long Hair, since those genes are usually available and easier to understand. Banding is a dominant gene that only requires one gene to express it's phenotype. So BaBa and Baba will both produce a banded hamster. BaBa is called homozygous and Baba is heterozygous. Long Hair is a recessive gene. This means it has to be homozygous ll to express it's phenotype (physical appearance).
We'll start with a Homozygous Banded & Short Haired BaBa LL hamster mated to a Solid Long Haired baba ll hamster. All offspring will be Banded carrying a gene for Long Hair Baba Ll. Now we'll mate one of the offspring to the Long Haired baba ll hamster. You would expect the Punnet square to look like this:
You would get one of each genotype and phenotype. However these genes are so close to each other they usually get inherited as a pair instead of individually. The ratio is roughly 9:1 for Parental type to Recombined type. So the actual outcome of this mating would be more like this:
As you can see it is possible to get a cross-over but more difficult then the normal genetic pairings. You would get 9 Banded Short HairedBaL/bal, 9 Solid Long Hairedbal/bal, 1 Banded Long HairedBal/bal, and 1 Solid Short HairedbaL/bal. You'll notice that the parental genes are listed as BaL/bal instead of Baba Ll. This is used with linked genes to signify the link between the two genes from the parents. I've used different colors for the original parental linked genes (BaL and bal) and the recombined parental linked genes (Bal and baL) to show where the new linked pairs are. The above chart is a short one for Banded and Long Hair. Below is a sibling pairing.
As you can see it is possible to get some recombining but more difficult then the normal genetic pairings. You would get the following phenotypes and genotypes:
The next linkage is with two recessive genes - C-locus and Cinnamon. There are currently 3 alleles for the Syrian C-locus: C is full color; cd is Dark Eared White; ce is Extreme Dilute. The linkage works the same for any allele on the C-locus since it is the location not the gene that causes the linkage. For this example I'll use the Dark Eared White (DEW).
Phenotypes and genotypes will be:
The last known linkage for Syrians is Satin and Umbrous. Both are dominant genes so there only needs to be one gene to express that phenotype. The ratio is also higher then the other two. This means it's less likely the parental genes will recombine.
Phenotypes and genotypes will be:
As you can see it is much more difficult to get recombining with this pair especially since 1156 animals would have to be produced to reach these ratios.
If you think this last square had high numbers there is a gene pair in rabbits that has a ratio of 600:1.
Yellow, Tortoiseshell & Non-Yellow
Normal females are XX and normal males are XY. The X chromosome is thought to be the primary chromosome from when we were one-celled creatures and didn't have two sexes. The Y chromosome is a truncated X chromosome and carries little genetic information other then maleness. For this reason the recombination that occurs with other linked genes does not happen with X-linked genes. A female that is X0 (only one X chromosome) will have all of the required traits of a female the same as a normal female. So only one X is required in females. Because of this a phenomenon called X-inactivation occurs. One of the two Xsbasically shrivels up and becomes inactive. This happens early in embryonic development. The embryo grows and more cells are produced from the cells that now have only one active X. These are daughter cells. When there is an X-linked gene it's possible to inherit two different alleles, one from each parent. This is the basis for the Tortoiseshell pattern. The female hamster inherits a Yellow gene from one parent and a non-Yellow from the other parent on her two X chromosomes. The size of the patterns depends on how early the X-inactivation occurs. Rarely more then one ova and one sperm join together or the splitting for the ova and/or sperm doesn't happen like it should. Since a male normally has only one X they can only be Yellow ToY or non-Yellow toY. Females can be Yellow ToTo, non-Yellow toto, or Tortoiseshell Toto. Below are four Punnet squares showing only yellow. Of course if you breed two Goldens together you'll get all Goldens. And two Yellows will give you all Yellows. This is assuming there are no recessives lurking in the gene pool. For a more in depth series of Punnet squares on Tortoiseshells go here. Most people put the Y in for the males to designate there are two genes but only the X can be Yellow.
This page was last edited on October 12, 2011