Vectis Hamstery and Exotics

Exhibitor and Breeder of Chinese Hamsters, Syrian Hamsters and Duprasi

Chinese Hamster Genetics

Like all animals, a Chinese hamster is made up of cells containing genetic material which it has inherited from its parents. This genetic material affects its appearance, health and behaviour. The inheritance of health and temperament is complicated as it involves many genes working together (polygenic) as well as environmetal influences. The inheritance of colour and pattern is better understood.

Genetics Introduction

Genetics is a subject full of strange terms and can seem daunting at first. This is, hopefully, a brief introduction to some of the main concepts as it applies to Chinese hamsters: chromosomes, genes, dominant and recessive. 


Genetic material is stored in cells as chromosomes which are coiled lengths of DNA. Chinese hamster cells contain 22 pairs of chromosomes. Chromosomes are made up of individual blocks of genetic information, or genes. These genes  provide information to the cell about building a specific feature, such as coat pattern. Genes traditionally are written in a shorthand of one or two letters in either upper or lower case letters, for example 'Ds' and 'ds'. 


The gene for the dominant spot pattern sits at on a specific area of the chromosome (also called a locus).  Each locus can contain only one gene for that feature, i.e. 'spotty' (Ds) or 'non-spotty' (ds). But remember that chromosomes come in pairs, so each cell has two genes for coat pattern, one on each chromosome. They can be different (spotty/Ds and non-spotty/ds) or the same (two spotties/DsDs or two non-spotties/dsds):

Some genes alter the hamster's appearance only when they are present on both chromosomes. This is referred to as a recessive gene and the gene code for a recessive gene is traditionally written in lowercase letters. In Chinese hamsters, the normal colour (or 'non-spotty' as I have been referring to it above) is a recessive gene, meaning that a hamster has to have two copies for it to be normal coloured. When genetic codes are written out, the non-spotty gene is usually referred to as 'ds' and a normal coloured hamster (which has two genes for the normal/non-spotty coat) is referred to as 'dads'.


Other genes alter the hamster's appearance when they are present on only one chromosome. This is referred to as a dominant gene and the gene code for a dominant gene is traditionally written in uppercase letters. In Chinese hamsters, the dominant spot coat (or 'spotty' as I have been referring to it above) is a dominant gene, meaning that a hamster only needs one copy for it to have a dominant spot pattern. When genetic codes are written out, the spotty gene is usually referred to as 'Ds' and a dominant spot hamster (which has one gene for the spotty coat and one for the non-spotty coat) is referred to as 'Dsds'.

A Chinese hamster receives one of each chromosome pair from each parent in the egg and sperm (also called gametes). The egg and sperm have half the number of chromosomes as the other body cells so that when they join to create the offspring, the offspring has the correct total of 22 .

Chinese Hamster Inheritance

In the UK there are three varieties of Chinese hamster with show standards: normal, dominant spot and black-eyed white. 


Dominant spot is, as discussed above, a dominant gene. Therefore mating a normal and a dominant spot Chinese hamster would result in a predicted 50% dominant spot and 50% normal offspring. Mating two dominant spot Chinese hamsters would result in 50% dominant spot, 25% normal and 25% 'double dominant spot' offspring. Usually these 'double dominant spot' offspring are reabsorbed in the womb and not born, resulting in smaller litters. In one linefrom the Netherlands, however, it appears that these 'double dominant spot' offsprings are not reabsorbed and are born as black-eyed white Chinese hamsters.

 

In a mating between two black-eyed white Chinese hamsters, the female appears to be pregnant and then resorbs the litter at about 14 days.














Two young black-eyed white girls

Please note that it is generally not recommended to breed two patterned Syrian hamsters (e.g. dominant spot or banded) in case they are carriers of the white bellied gene which produces deformed pups.

Punnett Squares

One way of working out the likely outcome of matings is to use a punnett square. This is effectivey another way of expressing the diagrams drawn out above using circles and arrows. In a punnett square, the possible genes in each egg/sperm for one parent are written on the x axis (horizontal) of the square and the possible genes for the other parent are written on the y axis (vertical) of the square. By combining the options in the boxes within the square, you get the possible outcomes of the mating. This is how I work out the potential percentages of dom spots, normals and BEWs in a litter.

.
 Ds
 ds
 ds
 Dsds
 dsds
 ds
 Dsds
 dsds

For example, the diagrammatic mating above showed a mating between a dominant spot (Dsds) and a normal (dsds) Chinese hamster. The punnett square has the dominant spot parent across the top and the normal parent down the left side.  


The potential offspring are two Dsds and two dsds, i.e. half of the offspring are expected to be dominant spot and half normal.

The following example is for the mating between two dominant spot Chinese hamsters:

.
 Ds
 ds
Ds
 DsDs
 Dsds
ds
 Dsds
 dsds

The potential offspring are two Dsds, one dsds and one DsDs, i.e. 50% of the offspring are expected to be dominant spot, 25% normal and 25% black-eyed white if the parents are from black-eyed white lines. If not, then the litter would be expected to be 66% dom spot, 33% normal (as the DsDs are resorbed in the womb).

Although it's good to breed with an aim in mind and work out what you are expecting from a litter, the ultimate deciders are the hamsters! These are photos of two litters from two different pairs of dominant spot Chinese hamsters (both from black-eyed white lines):