Chromosomes and DNA

  DNA (Deoxyribonucleic acid) is the blueprint for all different characteristics. Chromosomes contain DNA, and come in pairs of two. Rabbits have 22 pairs of chromosomes, or 44 total. Each one contains genes with DNA that determines every single characteristics that a rabbit has.

Dominant and Recessive Genes

Most genes come in both a dominant and recessive form. Dominant genes are written with a capital letter, such a 'A'. The 'A" stands for a certain gene. Recessive genes are written with a lower case letter, such as 'a'. It normally only takes one dominant gene to show that particular characteristic, but it takes two recessives to show a recessive characteristic. If there is one dominant and one recessive (called heterozygous), then the rabbit will show the dominant trait or a variation of it. If a variation of a dominant trait is shown, it is called incomplete dominance. Or, if both the dominant trait and recessive show up, it is called co-dominance. An example of this would be a roan cow or horse.

Rabbit Genes

  There are 10 color gene groups in rabbits. They are A, B, C, D, E, En, Du, Si, V, and W.  There are also recessive forms of these genes. On top of these, there are also modifiers, which modify a certain gene. These include the rufus modifiers, color intensifiers, and plus/minus (blanket/spot) modifiers. A rabbit's coat only has two pigments, yellow and dark brown. There can also be no pigment, causing a albino or white rabbit.

Color Genes

Within each group, the genes are listed in order of dominance (i.e. for the agouti group the agouti is most dominant, tan pattern is second most dominant, and self is least dominant).

*remember that lower case are recessive and capital letters are dominant*

"A" is the agouti color group (wild rabbit color). The genes in this category are:
A= agouti (chestnut, lynx, agouti)
at= tan pattern (tan, silver martin)
a= self or non-agouti (black, chocolate)

"B" is the black color group. The genes are:
B= black (chestnut, agouti, black)
b= brown (chocolate)

"C" is the color group. A chestnut will still be a chestnut, a black still a black, and so on.
C= full color (black)
cchd= dark chinchilla (chinchilla)
cchl= light chinchilla (seal point, smoke pearl)
ch= Himalayan (black pointed white)
c= albino (ruby-eyed white or REW)

"D" is the dilute group. For example, a black rabbit with this gene is a blue.
D= dense color (normal coloring, like a dominant C)
d= diluted color (blue)

"E" is the extension group. It works with the 'C' gene and rufus modifiers. When it is recessive, it removes all dark pigment.
Es= steel

E= normal dark pigment (black)
ej= Japanese brindling (harlequin)
e= no dark pigment (frosted pearl)

"En" is the plus/ minus (blanket/spot) color group. It creates the broken color pattern.
En= English spotting (broken, which is white and another color)
en= self (no white areas, solid color)

"Du" causes the Dutch color pattern, which is white on the head, white band behind the head, and white back feet.
Du= absence of dutch pattern
du= dutch pattern

"V" stands for vienna white, which is the blue-eyed white (BEW).
V= normal color
v= vienna white (BEW)

"Si" causes a silver color.
Si= normal color
si= silver color (silver, silver fox)

"W" works with the agouti gene and can widen the middle yellow-white band.
W= normal width of yellow band (chinchilla)
w= doubles yellow band width (New Zealand Red)



Punnett Squares
    Punnett squares are used to determine the probable outcome of a cross. In English, they help to figure out what could happen when you breed two rabbits (or anything else). For example, if I have a chocolate doe that I want to breed with a black buck, what colors could I get? That's when punnett squares come in handy. The difference in black and chocolate colored rabbits is the 'b' gene. In this cross, they will both be homozygous, meaning that they have the same two genes (example: bb) Here's how it's set up:

(chocolate) bb x BB (black) -each rabbit can pass on 1 allele.
                  b or b x B or B

     |  B  |  B | 
 b  | Bb |  Bb|
 b  | Bb |  Bb|
  All the babies are heterozygous black. Heterozygous means that they have two different genes. Black is totally dominant, so they will all be black. They will all carry the chocolate gene. If I cross two heterozygous chocolates, one out of four will be chocolate. I'll set it up:

    Bb x Bb
B or b X B or b
     |  B  |   b  | 
  B | BB |  Bb |
  b | Bb |  bb |

     There is one homozygous black, two heterozygous black, and one homozygous chocolate. Keep in mind that there might be more chocolates, or no chocolates all together! Punnett squares only determine probability, not frequency. They can be done with as many genes as you want! Just 'cancel' out all the homozygous pairs that are the same, and do the cross with the rest!

chocolate: aa bb CC Dd EE    

black: aa BB CC Dd EE

All the a's, c's, and e's are the same, so cancel them.

The cross is: bbDd x BBDd   Figure out all the possible combinations, then do it!

     | BD    | BD     | Bd     |   Bd   | 
bD| BbDD |  BbDD | BbDd | BbDd|
bD| BbDD |  BbDD | BbDd | BbDd|
bd|  BbDd |  BbDd | Bbdd  | Bbdd |
bd|  BbDd |  BbDd | Bbdd  | Bbdd |

   75% are black, 25% are blue.

    A tip for doing punnett squares is to always write the dominant gene first in the square, and the recessive after it. Keep the genes in order though (ABCDE...). In this last cross, I didn't cancel the 'Dd'. That is because they aren't homozygous. If I would have canceled them out, then I wouldn't have realized that I could get blue rabbits.
    Punnett squares can get a whole lot more complicated. I tried a cross once for fun that I was only able to cancel one gene pair out! It took a very long time to do. Most of the time, the more diversity in the genes, the more possible colors. The problem with this is that the colors might not be recognized in the particular breed. That can be good or bad, depending on the goals of the breeder.

NICE WORK! You just learned the basics of color genetics!

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