Answer: a) Cch x Ccch
b) Ccch x Cc
c) Cch x cchch
d) cchc x chc
Explanation:
<u>Data</u>:
- Coat color in rabbits is under the control of a single gene with
four alleles: C (full gray color); cch (chinchilla, light gray); ch
(Himalayan, white with black extremities); and c (albino, absence
of pigmentation).
- The dominance hierarchy is represented as: C >cch > ch > c.
<u>Possible genotypes</u>:
- <em>For full gray color</em>: CC (Gray), Ccch (Gray-2), Cch (Gray-1), Cc (Gray-3). The allele <em>"C" dominates over the other three alleles</em>, so in every combination where "C" is present, the animal will be fully grayed.
- <em>For light gray color/Chinchilla</em>: cchcch (Chinchilla), cchch (Chinchilla-1), cchc (Chinchilla-2). The allele <em>"cch" dominates over "ch" and "c"</em>, <em>but not over "C"</em>. So if the allele "C" is combined with "cch", the animal will be fully grayed, but in any other combination with "cch", the animal will be light grayed.
- <em>For white with black extremities/Himalayan</em>: chch (Hymalayan), chc (Hymalayan-1). The allele <em>"ch" that determines the Himalayan color is only dominant over the allele "c"</em>. But in combination with any other allele, "ch" behaves as a recessive one.
- <em>For albino</em>: cc. In the presence of any of the other alleles, the allele <em>"c" always behaves as a recessive one.</em> The only possibility of getting an albino animal is if "c" combines with another "c".
<u>Crosses</u>:
a) Gray-1 x gray-2
3/4 gray : 1/4 chinchilla
Parental) C ch x C cch
Gamates) C ch C cch
Punnet Square) C cch
C <em>CC</em> <em>Ccch</em>
ch <em>Cch</em> <em>cchch</em>
F1 Genotype) 1/4 <em>CC</em>
1/4 <em>Cch</em>
1/4 <em>Ccch</em>
1/4 <em>cchch</em>
F1 Phenotype) 3/4 Fully Gray animals (CC, Cch, Ccch)
1/4 Chinchilla animals (cchch)
b) Gray-2 x gray-3
3/4 gray : 1/4 chinchilla
Parental) C cch x C c
Gamates) C cch C c
Punnet Square) C cch
C <em>CC Ccch</em>
c <em>Cc cchc</em>
F1 Genotype) 1/4 <em>CC</em>
1/4 <em>Cc</em>
1/4 <em>Ccch</em>
1/4 <em>cchc</em>
F1 Phenotype) 3/4 Fully Gray animals (CC, Cc, Ccch)
1/4 Chinchilla animals (cchc)
c) Gray-1 x chinchilla-1
1/2 gray : 1/4 chinchilla : 1/4 himalayan
Parental) C ch x cchch
Gamates) C ch cch ch
Punnet Square) C ch
cch <em> Ccch cchch</em>
ch <em> Cch cchch</em>
F1 Genotype) 1/4 <em>Ccch </em>
1/4 <em>Cch</em>
1/4 <em>cchch</em>
1/4 <em>chch</em>
F1 Phenotype) 2/4=1/2 Fully Gray animals (Ccch, Cch)
1/4 Chinchilla animals (cchch)
1/4 Himalayan animals (chch)
d) Chinchilla-2 x himalayan
1/2 chinchilla : 1/4 himalayan : 1/4 albino
Parental) cchc x chc
Gamates) cch c ch c
Punnet Square) cch c
ch <em> cchch chc</em>
c <em>cchc cc</em>
F1 Genotype) 1/4 cchch
1/4 cchc
1/4 chc
1/4 cc
F1 Phenotype) 2/4=1/2 Chinchilla animals (cchch, cchc)
1/4 Himalayan animals (chc)
1/4 Albino animals (cc)
