Dutch Rabbit Genetics

by John W. Jones, Verlannahill Rabbitry

It’s A Question of Genetics

Question from Ashley:  I own a gray dutch buck. i just showed him in the florida state fair and he recieved 1st place and best gray dutch awards. i am looking into breeding him and i am also looking into purchasing a tortoise shell doe. my friend and i are going to start up our own rabbitry this summer and she owns 2 black dutches, one buck and a doe. i was wondering what color the babies would be if i bred my gray with her black doe and what color they would be if i bred him to a tortoise doe?? thank you so much. 

 

Color genetics in the Dutch Rabbit has been fairly well established for several years.  What I will draw on in trying to answer the question you presented is the way in which these genes, working in combination with each other, affect the appearance of the rabbit.  Without a basic understanding of how this takes place it is very difficult to explain or to understand what can be expected in the offspring when two rabbits of differing varieties are bred together.  

First of all I need to discuss a little about genetics in general.  Chromosomes are strands of DNA that act as the blue print that maps out the program that will be followed as the rabbit grows and develops into the unique individual it will eventually become.  In each cell, not including the sex cells and red blood cells, a rabbit has a total of 22 chromosomes.  Each one of these pairs controls a different characteristic about the rabbit.   For example, one might control the rabbit’s gender, while another set will control the density of the rabbit’s fur color, and another will determine the eye color.  Each chromosome pair is made up of two genes or gene pairs.  These genes may be the same, or they might be different, but there will always be two (with some exceptions due to genetic mutation that is beyond the limits of what we need to discuss here.)  A rabbit may for example inherit two genes for black fur, or it may inherit one gene for black and one gene for chocolate.  What is important to remember for our discussion here is that the rabbit will inherit two genes, one from each parent.  It is through this sharing of DNA that inherited characteristics are past down from one generation to the next.

When both genes are the same type of genes, in a certain chromosome pair, it is said to be homozygous for that particular gene. When there are two different genes, in a certain chromosome pair, we say it is heterozygous.   AA = homozygous   Aa = heterozygous. 

If a rabbit is heterozygous then one gene is usually said to be dominant over the other, meaning that it will be the one to cause an affect in the rabbit while the other gene, the weaker one, will be recessive and thus will just hide out and have no affect in how the rabbit will look though it can still be passed down to the rabbit’s offspring.  For example, if a rabbit had one gene for red eyes and one gene for brown eyes, the rabbit would have brown eyes because the gene for brown eyes is dominant over the gene for red eyes.  The gene for red eyes is then said to be recessive. 

Now without getting any more involved than necessary in the broader discussion of genetics let us concentrate on the five gene pairs that we know are responsible for controlling the coloration of the rabbit’s fur.  Generally speaking the five gene pairs that we usually are most concerned with are the A B C D and E series.

At the time of conception each baby rabbit will inherit one chromosome strand from each of its parents.  A single strand from the mother will combine with a single strand from the father with both coming together in the baby to once again form into the double strand of DNA that will form the blue print we talked about that has all the information needed to build a new rabbit.  What we are gong to concentrate on are just the five color gene pairs contained within the chromosome strands of DNA each rabbit has inherited.  How these genes combine into pairs will determine the coloration that will show up in your rabbit.  It will be very important that we pay careful attention to the dominant and recessive traits of each of the gene pairs.  The dominant or recessive nature of a certain gene pair can have a great affect in determining the base color of the rabbit and the density and appearance that color will have.

You may have come across in your studies in school the special way the genetic code is written by using groups of letters to represent the different gene pairs.  These letter groups make up the alphabet for writing the genetic code.  When the letters of the code are all put together it is referred to as the rabbit’s genotype.  The genotype for a black rabbit will be different than the genotype for a gray rabbit.  Some rabbit breeds will have more or less letters in their genotype depending on the particular breed and the number of genes known to play a role in determining specific characteristic.

The genotype for the coloring of the European wild rabbit might look something like this: AA  BB  CC  DD  EE   Keep in mind that there will always be a pair of like genes.  Two (A) genes, two (B) genes, etc.  Generally upper case letters are used to denote when the gene is considered dominant and lower case for when the gene is recessive.  You may have noticed that the genotype for a wild rabbit is all dominant.  Recessive genes are often the product of years of breeding for the purpose of developing certain genetic characteristics.    

Generally speaking most mutations that occur in an animal’s genetic code produce results that are undesirable.  Occasionally, however, mutations can occur that will have the affect of altering the appearance of the animal in ways that may result in pleasing colorations or distinctive markings that are considered particularly attractive.  When this happens a breeder will work to reproduce this characteristic over and over again within a breeding group until the trait becomes a consistent characteristic that can be repeated in each new generation of animals as the animals become capable of reproducing themselves as a distinct classification or breed.  Once that has been accomplished it is said that a new breed  has been created.  In the case of rabbits, the American Rabbit Breeders Association, ARBA, now currently recognizes a total of 45 domestic breeds of rabbits that are descendants of the original European wild rabbit. 

Within each breed there will normally be several different varieties that represent different color combinations and certain characteristics that are associated with a particular breed.  Each breed will have their own distinctive genotype along with certain dominant and recessive genes responsible for producing the distinctive varieties within the genotype.  For our purposes we will limit our discussion of genotypes to that of the  Dutch breed. 

The first letter in the rabbit’s genetics alphabet is the letter "A." This gene affects the basic pattern seen in the rabbit fur coat.

A

The A series of the alphabet is called the Agouti gene and it is this gene that causes a rabbit to exhibit the gray coloration that you see in your gray buck.  If you blow into your rabbits fur coat you will notice that each hair shaft is made up of a series of colored rings with each ring being a slightly different color beginning with slate blue at the base, followed by medium tan, then a tin charcoal brown and finishing with a lighter tan band.  Generally speaking, any rabbit having at least one dominant Agouti gene will be gray in color and exhibiting the Agouti banding.  There are exceptions to this rule depending on certain genetic modifiers that can occur within the E gene series.

Rabbits having the dominant (A) series Agouti Pattern have tan, white, or fawn markings on the belly, underside of the tail, inside of the feet and legs, inside the ears and nostrils, around the eyes, and in the shape of a triangle at the nape of the neck.  On the body, the fur has the typical Agouti rings that together produce the distinctive coloring of the agouti rabbit.

There are 2 recessive forms of the A series Agouti gene: 

at  Agouti Pattern causes the rabbit to have tan, white, or fawn markings on the belly, underside of the tail, inside of the feet and legs, inside the ears and nostrils, around the eyes, and in the shape of a triangle at the nape of the neck.  

What distinguishes this recessive gene from the (A) gene is the absence of the colored agouti rings around each hair shaft that are visible when blowing into the fur. This is not a desirable characteristic in the Gray Dutch.    

a: is called the Self Pattern.  In the presence of this recessive gene each hair is a solid color, and there are no tan, white, or fawn markings.  The color of the hair shaft is one solid color with no banding.  Black Dutch, Blue Dutch, Chocolate Dutch and all other solid colored rabbits will carry this recessive gene in their genotype. 

 

B 

B is the next letter in the genotype and tells us about the intensity of the color of the rabbit’s fur.

B  When this gene is dominate the rabbit will be BLACK in color meaning that the base color of the Dutch rabbit will be either black or blue.  

b  When this gene is recessive the base color of the rabbit will be Chocolate or lilac.



C

C  is the next letter in the genotype but it does not directly affect the Dutch breed. Though it may affect how deep and dark the base coloring is and also controls how much red coloring will be present in the coat.

C indicates full coloring with the red color fully expressed. 

c  indicates Albino – all color is restricted leaving the rabbit a pure white with red eyes.

 Other representations of this gene do not directly affect the Dutch breed and so will not be discussed here.

 

D

D is the next letter in the genotype.  This letter determines the amount of pigment there will be in each hair shaft.  The less pigment there is the lighter the hair color will be.  This gene is often called the Dilute Gene because it will dilute or lighten the base color

D indicates full pigment and no dilute of the base color.  The base color will be dense and fully expressed.

d  indicates less pigment in the hair shaft and a dilute base color.  A Black rabbit will appear Blue in color and a Chocolate rabbit will appear lilac in color.

 

E

The E gene is a very interesting part of the genotype of the rabbit and can produce some surprising affects.  It controls the banding of color rings that was mentioned when discussing the Agouti gene.  The (E) gene has control over how the rings of color are expressed.

Es  is often called the Steel gene and is responsible for producing the steel variety of Dutch rabbits.  This gene strips off the agouti pattern and extends the under color up the shaft leaving a mostly solid colored rabbit having some gold or silver tipped hairs.  Silver tipped is the preferred tip color.  This silver tip is what gives the steel its distinctive coloration.

E  gives the rabbit full extension of normal color on the hair shaft with no disruption of the agouti banding.  The rabbit has normal color, and the bands are not disturbed.

E(j)  Japanese - This gene takes the band of colors common to the agouti pattern and separates those colors placing them on different hair shafts.  This is the gene responsible for producing the Tricolor and Harlequin colored rabbits.

e Produces non-extension of color effectively removing the agouti pattern and leaving only what would be the intermediate band in a normal colored rabbit.  It is this gene that is responsible for Tortoise and Orange colors in Dutch rabbits.

 en:  Solid - The rabbit has no spots.

 

Okay, now please believe me when I say that this has been a very short and very simple discussion of color genetics in Dutch rabbits.  Our discussion has just touched the surface of this fascinating subject, enough so that we can have some base of understanding from which to answer your original question.  I would like to assume that you have been exposed to some study of genetics in your science classes.  Enough so that you are acquainted with punnett squares and have used them to help predict probability studies of genetic heredity.

 

Question 1 - what would be the result of breeding a Dutch Agouti gray to a Dutch Black?

Let’s look at the probable genetics of both rabbits.  Without actually looking at their individual pedigree I have no idea what different varieties of Dutch may have been introduced into either one of these rabbit’s bloodlines so we will need to approach this question realizing that there will be some unknown genes in each rabbit’s genotype.  We will represent these unknown genes by placing a question mark (?) where they would show up if we did know their identity.

Agouti  AA  B?  C?  D?  E? enen     Typical genotype for an Agouti Gray Dutch

Black   aa   B?  C?   D?  E? enen      Typical genotype for a Black Dutch

Note that in the case where we have placed question marks they are always placed next to a dominant gene of the gene pair.  Based on what we do know about your rabbit’s color we can establish that these genes would need to express their dominance in order to produce the characteristics we can observe in your rabbit’s coloration.  The second gene represented by the question mark could be dominant or it could be recessive based on past bloodlines in its pedigree.  For our immediate purposes it really does not matter, however once the litter is born you will have information that will be valuable in helping you to identify the recessive or dominate nature of these genes.

Okay: are you prepared to guess at the most probable color of the bunnies from this litter?

 Let’s begin by running what we know about the Agouti gene series through our punnett square.   

 

A

A

a

Aa

Aa

a

Aa

Aa

Notice that in all cases a recessive (a) gene is paired with a dominant (A) gene.  Because the dominant gene will determine how the agouti gene is expressed we can see that all the rabbits will inherit the characteristics of the agouti gray rabbit. (Aa Aa Aa Aa)

The answer to your question then is that most likely all the babies in your litter will be gray and there will be no Black bunnies.  For there to have been a Black bunny in the litter both Agouti genes would need to have been recessive.  But notice that each of the gray bunnies will have received a recessive agouti gene from its Black mother.

 

 Okay – let’s look at a possibility that would allow you to have a Black bunny in the litter.

You learned that dominant genes are the ones that normally determine the affect while recessive genes tend to hide out and are only passed down to future offspring.  What would happen if your Gray buck happened to have one recessive Agouti gene in its genotype?

 

A

a

a

Aa

aa

a

Aa

aa

Notice how things have changed in your punnett square.  Now half of your bunnies will have inherited recessive Agouti genes and because they will have Dominant (B) genes 50% of your litter could be Black Dutch while the other 50% will be Gray Dutch.

 

 

Question 2  what would be the result of breeding the Black to a Tortoise?

 

Let’s look again at your Black’s possible genetics.  Black   aa   B?  C?   D?  E? enen

And then the genetics of a typical Dutch Tort         Tortoise   aa    B?  C?   D?  ee  enen

 Notice that the Tortoise color carries both recessive (e) genes.  Should the Black doe be carrying a recessive e gene in the location of the unknown space in the E series then there is always the possibility of having a Tortoise show up in the litter.  The only way of knowing that question for sure is to try breeding the two rabbits.  If you happen to get lucky and a tort shows up in that first litter then you have your answer.  However if you fail the first time it does not necessarily prove the nonexistence of the (e) gene, only that it failed to be passed down the first time.  Only after three or four successive matings can you be reasonably confident that the gene does not exist in your Black.

 

Yes, working with genetics can mean a lot of work and much time spent breeding your rabbits in an attempt to get a particular trait to surface.  But then you said you two wanted to start a rabbitry.  Breeding animals is a time consuming project that requires a good degree of knowledge about what it is you are trying to accomplish plus how best go about achieving that end result you are after.

Sometimes the best choice is not to go about trying to reinvent the wheel again but rather just to go buy the wheel instead.  You may find that works well with rabbits too.  Maybe your best route would be to purchase a good Tortoise buck and doe and begin working at improving your line using them.  Your chances of success would be much better and with a lot less chance of discouragement.

John W. Jones

Copyright January 2006 All rights reserved

Verlannahill Rabbitry