Basic Genetic Principles
Although interested in genetics, I am certainly no expert and only just about understand the basics! For those of you who want to know more, there are many very informative websites but I am only going to discuss the basics.
There are 10 colour gene groups in rabbits. I have listed some of them below and described them here, with the dominant one (shown with the Capital letter), mentioned first and the recessive one, (shown with the lower case letter) second. The 10 groups are as follows: A, (Agouti or Non-Agouti) B, (Black or Brown) C, (Coloured or Albino) D, (Dense or Dilute) E, (Extension or Non Extension) En, (English Spotting or Self Coloured) Du, (Absence or presence of the dutch pattern) Si, (Non Silvering and Silver) V, (Absence of Vienna or Vienna) W, (Normal width or Wide band) and P, (No P Mutation or P Mutation). On top of these, there are modifiers which modify certain gene(s).
I will briefly just outline just the A, B, C, D and E genes. There are several variations on these basic dominant and recessive genes but I will just stick to talking about the 5 (A-E) series and their recessive forms (a-e).
The A Series: determines Agouti (A) or non-agouti (a)
A stands for Agouti. Since A is dominant, all agouti patterned rabbit carries at least one A gene.
a stands for non-agouti. a is recessive to A, that means an Agouti patterned rabbit may carry a gene but a non-agouti rabbit will not carry A gene.
The B Series: determines Black (B) or brown (b)
B stands for black. There are only two variations of black: black and blue. If a rabbit is a black or blue, the rabbit must carry at least a B. Whether it is a black or blue will be determined by the D series gene.
b stands for brown. In mini lop rabbits, it is called chocolate. There are two variations of chocolate: chocolate and lilac. If the rabbit is chocolate or lilac it must carry two b genes. b is recessive to B, so a chocolate or lilac rabbit can not carry B. Whether the rabbit is chocolate of lilac will be determined by the D series gene.
The C Series: determines Coloured (C) or Albino (c)
C stands for coloured: Most of the regularly coloured rabbits carry C. If you see a black, chocolate, chestnut agouti, tort,.... rabbit, you can be sure it carries at least one C gene.
c stands for albino. The appearance of the rabbit is ruby eye white. The rabbit may carry any of the genes in A, B, D, E series, but the cc genes act like a white sheet covering all other characteristics of the colour genes. c is the most recessive in the C series. Breeding two ruby eye white rabbits will result in nothing but ruby eye white.
The D Series: determines Dense colour (D) or dilute colour (d)
D stands for dense colour. Black, chocolate, chestnut agouti are dense colours, the rabbit must carry at least one D gene.
d stands for dilute colour. Blue, lilac, opal are dilute colours, the rabbit must carry two dd genes.
The E Series: determines Extension (E) or non extension (e)
E stands for extension. When a rabbit carries at least one E gene, the colour of the rabbit extends from base to tip. Black, blue, chocolate, lilac, chestnut agouti, opal, chinchilla,.... all of these rabbits has extended colours.
e stands for non-extension. Tort (sooty fawn), blue tort (beige or isabella), choc tort, lilac tort, fawn, cream, pearl etc. These are coloured rabbits but the body colour is different or lighter than the point colour. They all carry two copies of non-extension gene ee. As a result the true colour of these rabbits is not extended to the body, only the points carry the true colour. Example, a Chocolate Tortoiseshell is a chocolate rabbit whose chocolate colour is not extended over its body.
The Chocolate Tortoiseshell (aa bb C_ D_ ee)
The colour of a chocolate tortoiseshell mini lop should be a clean bright orange blending to darker 'chocolaty' colour over the lower rump and haunches. The top colour is to carry down the coat and blend to a dark cream under colour next to the skin. The underside of the tail is to match shadings as close as possible. Shading on the head should be darkest along the jaw line, darkening again around the ear base blending the ears to match body colour. Chocolate tortoiseshells have brown eyes. They start out life being quite pale in colour but the chocolate shadings darken with maturity. (as you will see below)
Some examples of torts (mostly bred here) ...
The developing Chocolate Tortoiseshell...
Please note these photos demonstrating the choc tort colour ONLY (not type!) - a lot of these photos were years ago when I first started to develop this gorgeous colour on this wonderful breed. I will continually add to these photos to give a fuller gallery of a growing chocolate tortoiseshell!
* Please note that these photos have been taken to help other breeders identify chocolate torts. I would not ever recommend taking babies out of the nest and certainly not on day 1.
a) it can really upset the doe who may react badly from the stress which could result in disaster. The babies in the photos below at 2 and 3 days were from Minstrel who is an old hand at motherhood and I often liken her to a soppy old dog. She has no objection what so ever.
b) because the babies have no real quantity of fur and like human babies, need help in keeping warm (in the form of their siblings and the nest their mother has made).
c) As well as the above two reasons, the flash can damage the underdeveloped eyes- so if you are taking a photo of the babies in the nest, turn the flash off!!
Day 2. Two torts, bottom and the little bottom poking out, in this litter of 7 (the others are selfs)
A Chocolate Tortoiseshell Mini Lop on day 3.
The next few photos are taken on day 4. As with the above photo, I don't know why it looks so dark- this was in the middle of a warm day!!
3 Weeks. (note how the chocolate shading darken at around this age. These 3 brothers/sisters are at different stages in the development of their colour) And as with sooties, they do vary in darkness!!
8 weeks. The left photo is a tort bred here and the photo on the right is bred by another breeder. Note the difference in shading the lighter one will I am sure develop but obviously it is slower to mature.
12 Weeks. Note how the chocolaty points have becoming darker.
An adult in moult. Note how chocolaty the mask on the face now is. This is also present up the flanks and on the ears, blending to match body colour but this tort is in moult and looks quite different. You can see the chocolate around the face but only glimpses of it elsewhere.