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Everybody who had to do with it voluntarily or unvoluntarily knows: the genetics around the guinea pigs is hard to learn and to understand, and you need a certain "bite" to really learn it, you have to really want to learn it! I find it very important to know genetics if you want to be a good and thorough breeder. If you have any questions regarding genetics, I will be pleased to help you, just send me an e-mail. Note that the abbreviations and letters used for the genetic factors are sometimes different in foreign literature, however, that doesn't change the basics of the inheritence at all, the literature is just not unique in the way it names the factors. Where known, I will mention other possible ways of how it is written in other countries.
Now first some basic knowledge about inheritence in order to be able to better understand the following genetic formulas for the colors of the guinea pig:
The DNA (Desoxiribonucleinacid) is the carrier of the genetic information for all creatures. She is made up of threads (or chains) which are winding through the cell nucleus. Single partitions of these chains - the ones forming a functional unit (per example for length of hair, color of eyes, etc.) are called genes. Genes are laid on the DNA in a recurring order thus every gene has its location on the chromosome. This location is called locus.
HOMOCYGOTE/HETEROCYGOTE
Every locus has several possibilities for how the genes look. If two genes on one locus are the same, then the animal is homocygote (breeds true) for this trait. However, are the gens different, then the animal is heterocygote for this trait (not breeding true).
DOMINANT/RECESSIVE TRAITS
It is possible that one gene suppresses another gene on the same locus. This suppressing gene (for the heritage formulas for the colors which follows always expressed with capital letters) is called dominant, the suppressed gene (expressed with small letters) is called recessive. It is also said that the animal "carries" a trait for example carries the color chocolate. When an animal has the color fomula Bb, its appearance will be black because the letter B stands for the dominance of the color black over the recessive b standing for chocolate. But the animal carries the color chocolate as a suppressed gene. The animal with BB is homocygote, i. e. breeds true for black, the animal with Bb is heterocygote (see above).
PHENOTYPE/GENOTYPE
The genotype is the genetical buildup (the genetic appearance) of an animal with all genes, recessive and dominant (see above). The phenotype is the obvious appearance of the animal, how it actually looks, the recessive genes are not visible, i. e. you cannot necessarily conclude the genotype of an animal from its phenotype.
MELANINES
are dark pigments which are produced in the body. The basic matter for them is tyrosine (an amino acid). Through different enyzmes it is enriched to a chain which is becoming gradually darker which is called polymerisation.
In the case of the guinea pigs, we always proceed from the original or wild color which is the agouti color of the wild guinea pig. All colors known today evolved through mutations from this original color - the formula for the color golden agouti
ABCEP
ABCEP
The color formulas are always written down like this. The two rows of letters in the formula stand for the two genes on one locus which can be the same - as in this case - or can in other cases be different (see also dominant and recessive traits). The abbreviations in this formula, which I will closely describe later, stand for the following:
A = Agouti Factor
B = Brown Factor
C = Color Intensitiy Factor or so called "Albino Factor
E = Extension Factor which is responsible for the relation of black and red colored hair (as well as their dilutions) in the coat.
P = Pink Eye Factor
THE A FACTOR
The following mutations are known, named in the sequence of their dominance to the next factor:
A = Normal Agouti without ticked belly
a(r) = Solid Agouti with ticked belly
Note: the small letters in parentheses are normally letters written as exponents and belong to the factor. For technical reasons, I had to write it in parentheses.
a = Self (Non-Agouti)
THE B FACTOR
There is only one mutation known here (this is not a dilution as is often erroneously assumed or mentioned):
B = Black
b = Brown (Chocolate) , normally has a ruby cast to the eye
THE C FACTOR
The known mutations of the C Factor reduce the pigments of coat, skin, and eyes. The red (yellow) pigment is affected stronger than the black (brown) pigment (see melanines). The factors are listed in the sequence of their dominance to each other (however, the factors are in many situations incompletely dominant).
C = Full intensity (intense colors and color combinations, black and red not diluted
c(d) = Light dilution (black dilutes to dark or medium sepia , red dilutes to buff)
c(k) = Also a light dilution (allows for more black than c(d) - produces dark sepio and also buff)
c(r) = Ruby eyed dilution, suppresses the red (yellow) factor - red is diluted to white. Also known as the chinchilla factor. Animal has ruby eyes.
c(a) = In other literature also written c(h). Also known as the Himalaya factor or dilution and responsible for the Himalayan markings
c = This mutation, which would stand for albinos in other animals, is not known for guinea pigs. Animals, who appear to be completely without pigment, are normally produced through a combination of c(a) and e (pink eyed white).
THE E FACTOR
Also called the extension gene. Here there are also three mutations known. The E factor influences the relation of black/brown towards red/yellow pigment and the distribution of these colors over the body.
E = Full extension: black or chocolate and their dilutions (lilac, beige) extend all over the coat
e(p) = Partial extension: animals with black and red coat (tortoiseshell, brindle and japanese markings)
e = Non-Extension: allows for only red pigment and its dilutions (golden, saffron, buff, cream and white) in the coat
THE P FACTOR
The P Factor almost only influences the black/brown pigment - red and its dilutions are hardly changed
P = Dark eyes
p(r) = Ruby eye , might me responsible for the color we call Slate Blue in Germany and the formula of which has not been completely clarified) and the dark eyed golden animals. In other literature also expressed as p(g)
p = Red eyes
In addition to these factors, there are two more factors, the so called spotting factor S and the so called dalmatian or spotted roan factor Rs. Other literature refer to these genes as Wh. (In Germany we also call it the lethal factor)
The White Spotting Factor
Responsible for the white patching of an animal
S = No white patches
s(s) = less than 50% white patching
s = more than 50% white patching
THE SPOTTED ROAN FACTOR
This gene is responsible for the dalmatian and roan markings of the guinea pigs. It is also called the lethal factor. This is a gene which causes non-viability in the homocygote form (RsRs). This means that dalmatians and roans are the carriers of the lethal factor (Rsrs). However, if you breed dalmatians and/or roans, the gene is doubled and produces white animals with certain deformities which are usually non-viable. Therefore dalmatians and/or roans should not be bred with each other. They should always be bred to self animals. Since it cannot be excluded that a white animal might be a so called "covert" roan or dalmatian, they should also not be bred with dalmatians and/or roans.
RsRs = lethal animals
Rsrs = dalmatian and roan markings
ABCEP
ABCEP Golden agouti, all genes are dominant = original/wild color
a(r)BCEP
a(r)BCEP Golden solid
ABCe(p)P
ABCe(p)P Goldenagouti and Red, e(p) allows for red spotting
I will call the remaining agouti colors by the two colors they show to avoid misunderstandings because the names for the different agouti colors are not the same in other countries to what we call them in Germany. I put the name we use here in Germany in parentheses in case somebody is interested. AbCEP
AbCEP Chocolate-Red (or Golden)-Agouti (Orangeagouti), B turns to b, black turns to brown
ABc(r)EP
ABc(r)EP Black-Silver-Agouti (Silveragouti), C turns to c(r), c(r) replaces the red hair tips with silver
Abc(r)EP
Abc(r)EP Chocolate-Silver-Agouti (Cinnamonagouti)
ABc(r)EP
Abc(d)eP Black-Buff-Agouti (Greyagouti), Cross between silver agouti and buff/cream)
Abc(r)EP
Abc(d)EP Chocolate-Cream-Agouti (Cremeagouti)
ABCEp
ABCEp Lilac-Golden-Agouti (Salmonagouti), because of the P Factor, black dilutes to lilac and red dilutes to "salmon" (golden)
Abc(r)Ep
Abc(r)Ep Lilac-White-Argente or Lilac-White-Agouti
aBCEP
aBCEP Self Black, golden agouti without the agouti gene
abCEP
abCEP Self Chocolate, Non-agouti, b turns black to brown
aBCEp
aBCEp Self Lilac, Non-agouti, p dilutes black to lilac
abCEp
abCEp Self Beige, Non-agouti, p dilutes brown (chocolate) to beige
??CeP
??CeP Self Red, Question mark instead of A: because of the gene e, all black is suppressed in the animal, however, every animal from the red color line can be an agouti. Question mark instead of B: each animal from the red color line can be either B or b. If the animal has a ruby cast to the eyes, it carries chocolate.
??Cep
??Cep Self Golden, dark eyes
??c(d)ep
??c(d)ep Saffron - Buff with red eyes, in other literature often expressed as c(k)c(k)
??c(d)eP
??c(d)eP Buff , also expressed a c(k)c(k)
??c(d)eP
??c(a)eP Cream, not breeding true, mix of buff and white
??c(r)eP
??c(r)eP Dark eyed White, red color turns to silver (white) because of c(r)
??c(a)eP
??c(a)eP Pink eyed White, e with c(a) is a pure white animal with red eyes, the dilution leading to dark eyed white and pink eyed white animals is not produced by the P Factor but by c(r) and c(a) therefore they are both PP
aBc(a)EP
aBc(a)EP Black Himalayan, here also the dilution due to c(a), however, EE allows for black causing the black extremities on Himalayans. The same formula with bb = Chocolate Himalayan
aBCEPs
aBCEPs Black Dutch or any other self animal with white spotting
??c(d)ePs
??c(a)ePs Cream Dutch or any other cream and white marked animal, as an example
aBCe(p)Ps
aBCe(p)Ps Tortoiseshell and White, black and red animal with white spotting
aBCe(p)P
aBCe(p)P Brindle, Japanese or Brindle, black and red animal without white patching
aBCEPSRs
aBCEPSrs Black Dalmatian or Roan (see RsRs = Lethal Factor)
L = Short hair
L = Long hair (incompletely dominant, when breeding short and long haired animals, the first generation may already have animals with half long hair or single, longer hair strands - the so called "tails" or "skirts"
St = Crested (Star) (the crested gene is a dominant gene, i. e. breeding cresteds and non-crested will already yield at least 50 % crested in the first generation)
st = Non-Crested
Rh m = Abyssinian
rh m = Smooth hair (here also an incomplete dominance, breeding abyssinians to smooth haired animals usually yield youngsters with less than 8 rosettes which are also bad of form and order. M stands for a modifier gene which is responsible for the order, form and/or number of rosettes, there are probably several modifier genes working)
Rx = Smooth hair
rx = Rex/Texel
Fz = Smooth hair
fz = Teddy
Sn = Non-Satin
sn = Satin
