Basics of Genetics in Syrian Hamsters

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Prologue:

My purpose in writing this article is to explain as simply as possible the basics of genes in the Syrian hamster. I am certainly not an expert and my knowledge is limited to what I have read and my experiences breeding my own hamsters. Genetics are extremely complex and I have tried to simplify it as much as possible but have sacrificed a thousand details to do this.


I would like to make clear that the purpose of this article is NOT to encourage anyone to try to breed his or her own hamsters. No one UNDER ANY CIRCUMSTANCES should ever put two hamsters together to breed just to see what happens. That is irresponsible, reckless and dangerous for the hamsters. There are many, many factors that must be seriously taken into consideration BEFORE anyone attempts to breed hamsters of any species.


If you would like to contact me, I can be reached through this forum or you can email me at HamstersInc@rogers.com. Christine Yule, Hamsters Inc.



Basics of Genetics in Syrian Hamsters

Inside the nucleus of each cell of a hamster is something called Deoxyribonucleic Acid or for short DNA. DNA is a molecule that contains a blueprint of instructions. Genes are made of DNA. Every detail about the hamster is recorded in the genes including its appearance and temperament.

Where do these genes come from?

Biological children resemble their parents. Why is that? It is because they inherited genes from their parents. For example, you might have the same color of eyes as your mother but have the same color of hair as your father. The genes of your mother and father determine all of this. The same applies to hamsters. The genes they inherit from their parents determine their appearance, too.


Genes are made up of DNA. This DNA is wrapped up and is packaged into chromosomes. Chromosomes exist in sister like pairs. Syrian hamsters have 22 pairs of chromosomes and some of the genes within those chromosomes determine what the hamster will look like. In the wild, Syrian hamsters were basically all the same color. This color is called Golden. The genes that determine that color were passed from generation to generation, producing hamsters that were basically the same color, Golden.


How are genes passed from parents to hamster pups?

When a hamster is conceived, it needs to have 22 pairs of chromosomes. The pup's mother has 22 pairs and its father also has 22 pairs. The pup inherits a copy of one half of each chromosome pair from its mother and a copy of one half of each chromosome pair from its father. The pup ends up with 22 pairs of chromosomes that are a combination of both mother and father. One half of a gene is called an allele and is represented by letters of the alphabet that have been chosen to represent a certain gene. In the example #1, the chromosome pair is (EE). One half, or "E" by itself is called an allele.


One allele from a chromosome pair is randomly chosen in nature from the mother and is copied and given to the pup. One allele from the matching chromosome pair is randomly chosen from the father and is copied and put together as a new chromosome pair for the pup.

Image:Genetics02.jpg

In this example the only combination possible is (EE). All pups inherit the same color gene from the parents. Therefore, all pups are the same color as their parents. That color is Golden.

Golden Hamster

Image:Genetics03.jpg


What can make a hamster look different from its parents?/Mutations

Sometimes mutations occur within the nucleus of a cell. Gene mutations occur when the fundamental intermolecular structure of a gene is altered. In other words, the gene is changed somehow. When these mutations occur within the germ cells, they can be passed on to offspring. Some of these mutations may affect the appearance of the hamster.

The genetic makeup of a normal hamster contains thousands of genes that are arranged in pairs. The normal gene (E) is paired with another normal gene (E), producing a gene pair of (EE). When a normal gene mutates, the mutation becomes the other half of the normal gene's pair. When the normal allele (E) mutated, it produced the mutation (e). Therefore the chromosome pair of that hamster becomes not (EE) like its parents but becomes (Ee). The pup now has a different genetic code from either of its parents. When the chromosome has matching alleles, either (EE) or (ee) for example, it is said to be homozygous. When the chromosome has two different alleles, such as (Ee), it is said to be heterozygous. Genes are put into different categories depending on how they "act" when being inherited. Most of these genes can be classified as either dominant or recessive genes.


What is a phenotype? A phenotype is a written record that represents a portion of the hamster's genetic makeup. It is a record of any genes that the hamster possesses that can be seen in its appearance.

What is a genotype? A genotype is also a written record of a portion of the hamster's genetic makeup. It is a record of any dominant and recessive genes the hamster may possess that are not obvious by just looking at its appearance.

What's the difference? The phenotype of a hamster is determined by appearance alone. If a hamster carries one allele of a recessive gene, it most likely will not be visible in its appearance. The genotype of the hamster is a record of both dominant and recessive genes that the hamster possesses. Therefore, when breeding for specific colors, it is helpful to know the genotype of the hamsters being bred together. Breeders should keep accurate records of the genotypes of the hamsters they breed to keep track of any recessive genes that may be present.


What is a Dominant gene?

A gene is dominant when one allele is present in the chromosome pair and that gene is visible in the animal's appearance. Genes are given an alphabetic code. The code of a gene that is dominant is always capitalized. For example, the Silver Grey gene is dominant and the alphabetic code is capitalized (Sg).

Chromosomes must exist in pairs, so when writing a hamster's genotype, both gene locations must be represented. For example, if a hamster inherited one Silver Grey allele (Sg) then there must be a sister allele to this Silver Grey allele. If the hamster inherited another Silver Grey allele (Sg) from its other parent then the pups genotype would be written as (SgSg). The chromosome pair would be one dominant Silver Grey gene (Sg) plus the dominant Silver Grey gene (Sg) from the other parent. (Sg) plus (Sg) equals (SgSg). However, if the pup inherited only one Silver Gray allele from one parent then its genotype would be (Sgsg). The second half of the pair would be represented by (sg). Since Silver Grey (Sg) is a dominant gene the opposite sister gene must be recessive and is written in lower case as (sg).


Since Silver Grey is a dominant gene, a hamster that has only one Silver Grey gene (Sgsg) will be Silver Grey in color. A hamster that inherits two dominant Silver Grey genes (SgSg) will also be Silver Grey in color.


What is a Recessive gene?

A gene is recessive when two matching alleles must be present to be visible in the animal's appearance. If only one recessive allele is present, the dominant allele will be apparent. The recessive gene will be hidden from the hamster's appearance but can be passed on to the offspring. The alphabetic code for a recessive gene is represented in lower case. For example, the Black gene is recessive and is represented by the small letter (a).


A hamster that inherits one recessive Black gene from one parent and another recessive Black gene from the other parent will have the genotype (aa). It will be black in appearance. However, a pup that inherits one recessive Black gene (a) from one parent but does not inherit a recessive Black gene from the other parent would have the genotype (Aa) and would NOT be black in appearance. TWO recessive genes are necessary to affect the hamster's appearance. If only one recessive allele is inherited then the other allele is dominant and must be capitalized.


How did different colored hamsters appear?

When Syrian hamsters were in the wild most mutations did not survive and disappeared. Hamsters continued to be the same color, generation after generation. However, when hamsters are bred in captivity, mutations are watched for and when a mutation that produces a desirable affect occurs it can be isolated and reproduced through selective breeding. Over the past few decades many different gene mutations have appeared.


Let's show in an overly simplified way, how a new recessive gene mutation can appear.


Let's take a male Golden hamster with the genotype (EE) and a female Golden hamster with the genotype (EE). One day a mutation occurs and is passes on to one of their pups. This pup now has a different genotype that either of its parents (Ee). (See Example #2) In this case it is a recessive gene and therefore the pup will look like its parents but will possess a recessive gene that can be passed on to its offspring when it breeds. This hamster is said to "carry" the recessive gene.


Image:Genetics04.jpg

The pup with the genotype (Ee) matures and breeds with another Golden hamster with the genotype (EE). (See Example #3)

Image:Genetics05.jpg

Some pups will receive a copy of the (E) gene from the mother and a copy of the (E) gene from the father. Therefore, the genotypes of some pups will be (EE) and be Golden in color.


There is another possible genotype for some pups. (See Example #4) Some pups will inherit a copy of the (E) gene from the mother but may receive a copy of the (e) gene from the father. These pups will have the genotype (Ee) but will also be Golden in color. However, they are said to be "carrying" (e), although it does not show in their appearance.


Image:Genetics06.jpg

Now, let's take a female pup with the genotype (Ee) and a male pup with the genotype (Ee). Some pups may inherit a copy of the (E) gene from its mother and the (e) gene from its father and have the genotype (Ee). (See Example #5)


Image:Genetics07.jpg

There is also this possibility. Some pups may inherit one copy of the (E) gene from the mother and the (E) gene from the father and have the genotype (EE). These pups will be Golden in appearance and will have no trace of the recessive (e) gene. (See Example #6)


Image:Genetics08.jpg


There is also this possibility. Some pups may inherit a copy of the (e) gene from the mother and a copy of the (e) gene from the father. The genotype of these hamsters will be (ee). They now have a completely different genotype from their parents. (See Example #7)


Image:Genetics09.jpg


Since this is a recessive gene that is homozygous, it will change the appearance of the pups. Instead of Golden in color, the pups will be a gene mutation called Black Eyed Cream (ee). Therefore, a new color gene mutation is born!


Instead of all the pups appearing Golden, a pup is born like this!


Black Eyed Cream

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How does this color survive? Let's see what happens when a Black Eyed Cream pup with the genotype (ee) breeds with another Black Eyed Cream pup with the genotype (ee).


Image:Genetics11.jpg


The only genotype their pups can inherit is Black Eyed Cream (ee). Therefore, all pups will be Black Eyed Cream in color.


Genetic mutations can affect the coat color of a hamster but they can also change the hair from the normal short hair to long hair or even to wavy hair like the rex gene. They can also produce varying patterns of white in a hamster's coat.

A following article in this series will discuss some of the mutations that affect Syrian hamsters.



Written by by Christine Yule.



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