Download Genetic Coat Colour Determinism in Rabbits

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ORIGINAL SCIENTIFIC PAPER
Genetic Coat Colour Determinism in Rabbits
Dana Pusta1, Zsigmond Rakossy2, Rodica Sobolu3, Ioan Paşca1
1
Faculty of Veterinary Medicine, University of Agricultural Sciences and Veterinary Medicine
Cluj-Napoca, Romania ([email protected])
22
SC Bubo-Vet SRL, Păuleni-Ciuc, no.67, Romania
3
Horticulture Faculty, University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca,
Romania
Abstract
The purpose of the study was the presentation of the main colors (phenotypes) found in
rabbits, establishing their genetic determinism and obtaining the most various and rare
phenotypes. The basic genes for the coat color in rabbits are the following: A –
normal/chinchilla,/albino, B – red/fawn, C – normal brown (lilac), D – dilution of color
(blue/lilac) and G – agouti, tan/otter/marten-self and the coat color is also influenced by K
gene, also called English broken. The results obtained after different cross-mating allowed
us to determine the recessive genes of the genitors and also to obtain new and rare colors.
We recommend rabbit breeders to solicit the advice of specialists so that by cross-mating
to obtain the desired results.
Key words: color determinism, rabbits, phenotype, genetic determinism, test-cross
Introduction
The coat color in rabbits is determined by the concentration of different coloured pigments
into the hair. Diversity of their concentration determines the color intensity, respectively
lighter or darker. The black and brown pigments are called eumelanines and the beige,
yellow and red are called pheomelanines. Both types of pigments are the result of splitting
and oxidation of the tyrosine amino acid. (Griffiths et al., 2000.).
In rabbits in the process of eumelanin formation participates, not only one gene but a group
of genes which interact epistatically or complementary. The activity of these genes is also
influenced by other genes named modifying genes. (Robinson, 1958.). The synthesis of
melanin in rabbits is influenced by, at least, five pairs of genes, placed in the same number
of loci, symbolised as follows: A, B, C, D, G (European symbols, used in this paper,
because in USA the symbols are different). (www.rabbitcolors.info). There are five basic
sets of genes which determine the coat color and several genes which change the coat
color. The basic genes are A –normal/chinchilla,/albino, B – red/fawn, C – normal brown
(lilac), D – dilution of color (blue/lilac) and G – agouti, tan/otter/marten-self. The coat
color is also influenced by K gene, also called, English broken, which determines the spots
on the coat (Holdas, 2002.). Genes in the organism are in double quantity in each of the
five loci, because the embryo is the result of the equal participation with hereditary
material of the both parents.
Material and methods
The experiments were made on two groups of rabbits, private property, in which initially
existed seven coat color varieties, such as: agouti, albino, black, Himalayan, chinchilla,
Thuringer and English broken pattern.
The agouti color is the typical wild rabbit color pattern. The individual hairs have two
colors, at its base and top is black and the middle is yellow. Beside this, the rabbits would
have white bellies, white eye circles and white on the underside of the tail. The genetic
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Stočarstvo
determinism of the agouti color is the following: A_B_C_D_G_. (Sandu, 1986.)
The albino color will eliminate the display of color in the rabbit. Because of its properties
when the gene is in pair (aa) have an epistatic interaction and will effect every other gene
set as well, as it will wash out the effect of the other genes. So, the color of the coat and
nails is white and the color of the eyes is Ruby – Red . The genetic determinism of the
Ruby-Eyed White gene is: aa _ _ _ _. (Vintilă, 1981.).
The black color appears in the case in of the agouti color in which the G dominant is
replaced by gg, as consequence the yellow color in the hair disappears and it becomes
uniform all black. The genetic determinism of the black color may be A_B_C_D_gg,, but
it also can be achi_B_C_D_gg. (Bud, 2005.).
The Himalayan color is white, uniform on all the body except the extremities, respectively
ears, legs, tail and nose which are black. The genetic determinism is ananB_C_D_gg..
The chinchilla color is a lighter variety of the agouti color, in which the yellow color in the
middle of the hair turns into white and the rest of the body is white, as agouti is. The
genetic determinism is achi achiB_C_D_G_. (Vintilă, 1981.).
The Thuringer color is yellow-ochre with guard hairs that are bluish-black. The very dense
coat of this breed is luxurious and has a silky texture. The color shade of the stomach is
charcoal which extends to the nose, ears, chest, lower portion of the shoulders, flanks,
bottom, tail, and legs. This shading is more predominate on the face area and fades towards
the rear of the body.( http://www.helium.com/items/1357186-rabbit-breed-profilesthuringer). The genetic determinism is; A_bbC_D_gg. (Vintilă, 1981.).
The black English broken pattern is a spotted pattern, the base color is white (30-70%), and
the spots are black. It is a color which appears in animals which are heterozygous on the K
locus. The hereditary formula is: A_B_C_D_ggKk. (Vintilă, 1981.).
In order to be able to establish the involved genes there were made the following crosses:
a) in order to establish the albino genotype, the albino female was crossed with three
different colors of males, such as Thuringer (A_bbCCDDgg), Himalayan (ananB_C_D_gg)
and Black himalayan (A_B_CCDDggKk) resulting 8 offsprings of albino color
(aa_bCCDD_g), 2 thuringer (AabbCCDDgg), 1 yellow (AabbCCDDGg), 3 agouti
himalayan (an_B_C_D_G_), 2 black (AaB_CCDDgg), 2 black himalayan
(AaB_CCDDggKk) and 1 agouti (AaB_CCDDG_).
b) in order to establish the recessive genes in Thuringer color (A_bbCCDDgg), a Thuringer
female was crossed with Thuringer, Himalayan and Black English broken males, the
resulting offspring confirming the presence of AA pairs of alleles.
c) the alleles genes were also determined in Chinchilla I (achi_B_CCDDG_) female using
crosses with Thuringer and Himalayan males.
Results and discussion
The purpose and the research objectives were to establish the genotype of the parents and
the obtaining of a large variety of new phenotypes.
After examining the phenotypes of the genitors, belonging of the two effectives determined
that we disposed by the following allelic genes: locus A: A, achi, an, a; locus B: B, b; locus
C: C; locus D: D; locus G: G, g and locus K: K, k.
In order to achieve the objectives, there were made multiple test-cross: test-cross with
homozygous and test-cross with heterozygous, which allowed the establishment of the
complete genotype of the breeders.
The albino color is a very interesting variant, because beside the allelic pair aa, the other
pairs of genes can not be deduced. This is the reason why one albino female was crossed
with three different males and analyzing the offspring genotype enables us to establish her
genotype.
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a)
♀ Albino (aa_ _ _ _)
X
♂ Thuringer (A_bbCCDDgg)
Results: 5 offsprings of albino color (aa_bCCDD_g), 2 thuringer (AabbCCDDgg) and 1
yellow (AabbCCDDGg)
Discussions: Considering the 5 albino (aa) we surely specify that the male also has a
recessive allele a. Because of the Thuringer color, which is A_bbCCDDgg, the female
must posses the recessive g gene. So the genotype of the parents is determined as:
♀
white: aabbCCDDGg and ♂ Turinger: AabbCCDDgg
b)
♀ Albino (aa_ _ _ _)
X
♂ Himalayan (ananB_C_D_gg)
n n
Results: 4 himalayan offsprings (a a B_C_D_gg), 3 agouti himalayan (an_B_C_D_G_)
Discussion: This result confirms that the allele an, responsible for the determination of the
Himalayan color is dominant upon the a recessive allele, and the light Himalayan color can
be explained by the presence of the G gene. So, the genotype of the male is
ananBBCCDDgg.
c)
♀ Albino (aa_ _ _ _)
X
♂ Black himalayan (A_B_CCDDggKk)
Results: 3 albino (aa__CCDD_g), 2 black (AaB_CCDDgg), 2 black himalayan
(AaB_CCDDggKk), 1 agouti (AaB_CCDDG_)
Discussion: The albino offspring proves the presence of the a gene in male. The agouti and
black colors confirm the presence og G and g gnes in the fmale genotype, which was
already shown after the first cross. So we ca conclude that the male genotype formula is
AaB_CCDDggKk
Considering the Thuringer color phenotype we surely say that the animal has A, bb, C, D şi
gg alleles, but is not sure if it posses other recessive alleles such as a, c, sau d. So, the main
purpose of the next crosses was to notice the presence of the albino color (aa) to the
offspring.
a)
♀ Thuringer (A_bbCCDDgg)
X
♂ Thuringer
Results: 5 thuringer baby rabbits (A_bbCCDDgg)
Discussions: Knowing from the first experiment that the thuringer male posses an a allele
we have expected to obtain the albino color after this mating. The result proves that the
female does not posses the a allele. The hereditary formula becomes: AAbbCCDDgg.
b)
♀ Thuringer
X
♂ Himalayan
Result: 7 black rabbit babies (Aan BbCCDDgg)
Discussions: Due to the fact that no himalayan baby rabbit was born (an_BCCDDgg), it is
confirmed that the female has on the A locus only AA alleles, which are dominant on an.
No thuringer (A_bbCCDDgg), was born, which confirms the absence of b gene into the
male genotype.
c)
♀ Thuringer
X
♂ Black English broken
Results: 3 black (A_BbCCDDgg), and 3 Black English broken (A_BbCCDDggKk)
Discussions: After the experiment 1 c didn’t result any thuringer (A_bbCCDDgg), which
confirms the fact that the male does not posses b allele. The result of 50% Black English
broken confirms Mendel laws. The resulted male genotype is ♂ Black English broken:
AaBBCCDDggKk
In the case of chinchilla color is well known that the rabbit posses the achi, B, C, D, G
alleles, but the recessive alleles are unknown (a, b, c, d, g).
a) ♀ Chinchilla I (achi_B_CCDDG_)
X
♂ Thuringer
Results: 2 black (A_BbCCDDgg), 2 agouti (A_BbCCDDGg), 2 Sallander
(achiabbCCDDgg), thuringer (A_bbCCDDgg)
Discussions: The formation of the black color (A_BbCCDDgg, or achi_B_CCDDgg)
demonstrates the presence of g allele and the agouti color (A_BbCCDDGg) confirm the
presence of G gene into the female genom. The Sallander (achi_bbCCDDgg) and thuringer
(A_bbCCDDgg) colors may be formed due to the fact that the female also posses, beside
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B and G alleles, the recessive alleles b and g. For Sallander color is also needed the
presence of a gene from the male which is recessive compared to achi. There wasn’t any
albino offspring which confirm that the chincilla female does not posses the a gene.So, the
resulted hereditary formula is: ♀ Chinchilla I: achi achi BbCCDDGg
b)
♀ Chinchilla I
X
♂ Himalayan
Results: 5 chinchilla (achi an B_CCDDGg), 2 black (achi an B_CCDDgg)
Discussions: This result proves that ach allele which is responsible for chinchilla color is
dominant over an. The resulted black color confirmes, that beside A_B_C_D_gg genotype
also achi_ B_C_D_gg may induce the black phenotype.
Similar to the third experiment in the fourth one we tried to obtain the recessive
phenotypes in the offspring.
a)
♀ Chinchilla II (achi_B_CCDDG_)
X
♂ Thuringer
Results: 3 black (A_BbCCDDgg), 2 chinchilla (achi_BbCCDDGg)
Discussions: Considering the resulted black color we may say that the female posses a g
allele, and the absence of albino denote that the female does not have the a gene. The
chinchilla color results because in the male genotype exists an a allele which is recessive
compared to achi. The absence of Sallander color (achi_bbCCDDgg) indicates that in the
female genotype does not exists b allele. The determined hereditary formula is: ♀
Chinchilla II: achiachiBBCCDDGg.
b)
♀ Chinchilla III (achi _B_CCDDG_) X
♂ Thuringer
Results: 3 agouti (A_BbCCDDGg), 2 black (A_BbCCDDgg, or achiaBbCCDDgg), 1 albino
(aa_bCCDD_g)
Discussions: The formation of the black color (A_BbCCDDgg, sau achiaBbCCDDgg)
demonstrates the presence of g gene on the G locus of the female. The albino offspring
proves the presence of a gene. The missing of yellow, thuringer or Sallander color proves
that b gene is missing into the female genome (all three cases request bb homozygous). So,
the genotype formula of the female is: ♀ Chinchilla III: achi aBBCCDDGg
c)
♀ Black (__B_CCDDgg)
X
♂ Thuringer
Results: 5 black (A_BbCCDDgg), 1 albino (aa_bCCDDgg)
Discussions: Considering the albino offspring (aa) we may conclude that the female also
posses an a gene. The absence of thuringer color (A_bbCCDDgg) among the offspring
demonstrates the b allele is missing from the female genotype. So, the resulted hereditary
formula for the female is: ♀ Neagră I (AaBBCCDDgg)
d)
♀ Agouti
X
♂Himalayan
Results: 5 agouti (Aan_bCCDDGg), 3 agouti Himalayan
Discussions: The absence of the black (A_BBCCDDgg) and Himalayan (ananBBCCDDgg)
confirmes the absence of g gene from the female genotype. The resulted agouti Himalayan
(anaBBCCDDGg) demonstrate the dominance of an allele upon a and also the dominance
of G over g. The hereditary formula of the female may be completed as follows: ♀ Agouti:
AaB_CCDDGG.
e)
♀ Agouti
X
♂ Himalayan
Results: 5 agouti (Aan_bCCDDGg), 3 agouti Himalayan
Discussions: The absence of black (A_BBCCDDgg) and himalayan colors
(ananBBCCDDgg) confirms the absence of g gene. The presence of agouti Himalayan color
(anaBBCCDDGg) confirms the dominance of the an allele over a and the dominance of the
G gene over g. The female hereditary formula becomes ♀ Agouti: AaB_CCDDGG
After the determination of the genotypes we made supplementary experiments for the
fixation of the resulted Sallander color in the effective and the obtaining of the new
phenotypes.
a) ♀ Black (AaBbCCDDgg)
X
♂ Sallander (achiabbCCDDgg) - resulted baby
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Results: 3 Sallander, 2 black
Discussions: This female was selected considering the a,b and g alleles which it posses and
which we need to repreduce the Sallander color (achi_bbCCDDgg).
b) ♀ Chinchilla I X
♂ Sallander
chi
Results: 4 pui black (a aBbCCDDgg), 3 Sallander (achiabbCCDDgg), 1 chinchilla (achi
aBbCCDDGg)
Discussions: This chincilla (achi aBbCCDDGg) female was selected because of the recesive
genes achi, b şi g.
c) ♀ Agouti (A_BbCCDDGg) – experiment 4, e
X ♂ Black English broken
(A_BbCCDDGgKk) – experiment 2, c)
Results: 4 black English broken (A_B_CCDDggKk), 2 agouti Himalayan
(A_B_CCDDGgKk), 1 Thuringer English Broken (A_bbCCDDggKk), 1 yellow himalayan
(A_bbCCDDGgKk), 1 albino (aa__CCDD_g).
Discussions: The male was selected because its mother was thuringer (AAbbCCDDgg) so
beside the K and k alleles it compulsory need to posses the b and g alleles, absolutely
necesary for the obtaining of the Thuringer English Broken (A_bbCCDDggKk) and yellow
Himalayan (A_bbCCDDGgKk) colors. The female was selected because its Thuringer
father mus posses the b and g alleles. The presence of the albino colors in the offspring
proves that both parents also posses the a allele.
Conclusions
Studying the genes which are involved in the genetic coat color determinism in rabbits we
succed to establish the genetic determinism of the new phenotyopes which have appears in
the effective, as follows: Thuringer English Broken: A_B_C_D_G_Kk, yellow:
A_bbC_D_G_; yellow Himalayan: A_bbC_D_G_Kk; Salander: achi _bbC_D_gg , agouti
Himalayan: an_B_C_D_G_; Thuringer English Broken: A_bbC_D_ggKk.
After the determination of the genitors genotype, by matching the pairs, we succed to
obtain five Sallander offsprings which will form the base of a new selection group.
We recommend rabbit breeders to solicit the advise of specialists so that by matching the
cross-mating to avoid the obtaining of unwanted colors, which are not accepted in
exhibitions and also to obtain some color varieties which are very rare in order to improve
the economical value of the individuals
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Dohy J. (1999). Genetika állattenyésztőknek, Mezőgazda Kiadó, Budapest.
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to Genetic Analysis, Seventh Edition, Ed. W.H. Freeman.
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http://www.rabbitcolors.info/
794 48th Croatian & 8th International Symposium on Agriculture | Dubrovnik | Croatia