Concept explainers
In a population of rabbits, you find three different coat color
a. | What can you conclude about the inheritance of coat color in this population of rabbits? |
b. | Ascribe genotypes to the parents in each of the 10 crosses. |
c. | What kinds of progeny would you expect, and in what proportions, if you crossed the chinchilla parents in crosses 9 and 10. |
a.
To determine:
The inheritance of coat color in this population of rabbits.
Introduction:
The gene refers to the functional and structural unit of life. The gene consists of two alleles. The increase in the number of alleles allows the generation of different phenotypes. There are four different alleles which are determining the coat color in rabbits.
Explanation of Solution
The four alleles determine the phenotype of rabbits. These are albino, wild type, chinchilla, and Himalayan. The phenotype of chinchilla rabbits have white hairs with black tips on the body, black hairs on extremities are present on Himalayan rabbits, albino has colorless hairs, and wild type has colored hairs.
The chinchilla rabbits are 75%, and the Himalayan rabbit is 25% from cross 3 data. This indicates that the dominant phenotype is chinchilla. The cross 5 contains 75% chinchilla and 25% albino rabbits. The chinchilla is dominant over albino phenotype. The cross 1 indicates Himalayan rabbits are 75% and 25% are albino rabbits. Thus Himalayan phenotype is dominant. This means inherited order is from chinchilla (cch) to Himalayan (ch) to albino (ca ) phenotype.
b.
To determine:
The genotypes of the parents in each of the ten crosses.
Introduction:
The genotype and phenotype are the two terms which describe the genetic makeup of the organism and also the physical character provided by a particular allele. The known genotype of parents helps in determining the genotype of offsprings.
Explanation of Solution
The two Himalayan individuals were crossed (cross-1). The phenotypic ratio is 3:1 of Himalayan and albino. This indicates complete dominance. The genotype of both parents is cchca. Thus the gametes would be cch and ca
♂/ ♀ | cch | ca |
cch | cchcch Himalayan |
cchca Himalayan |
ca | ca cch Himalayan |
ca ca Albino |
The cross (cross 2) between Himalayan and albino results in 1:1 phenotype. This indicates dominance. Thus the genotype of Himalayan parents is cchca (female), and albino is caca (male).
♂/ ♀ | cch | ca |
ca | cchca Himalayan |
caca Albino |
ca | cchca Himalayan |
ca ca Albino |
The cross (cross 3) between two chinchilla rabbits that results in a 3:1 ratio (chinchilla:Himalayan). The cross ( I case) have parental genotype Ccch (female) and Cca (male) and for II case is Ccch(male) and Ccch(female).
Cross for Condition I:
♂/ ♀ | C | cch |
C | CC Chinchilla |
Ccch Chinchilla |
ca | caC Chinchilla |
cacch Himalayan |
Cross for Condition II:
♂/ ♀ | C | cch |
C | CC Chinchilla |
Ccch Chinchilla |
cch | cchC Chinchilla |
cchcch Himalayan |
The cross (cross 4) between chinchilla and Himalayan parents results in all chinchilla phenotype. This is also a case of complete dominance. The genotype is CC (female) and cchcch or cchca (male).
Cross for Condition I:
♂/ ♀ | C | C |
cch | Ccch Chinchilla |
cchC Chinchilla |
ca | Cca Chinchilla |
caCa Chinchilla |
Condition II
♂/ ♀ | C | C |
cch | Ccch Chinchilla |
Ccch Chinchilla |
cch | Ccch Chinchilla |
Ccch Chinchilla |
The cross (cross 5) between two chinchilla parents results in 3:1 phenotype, i.e., chinchilla and albino. This is also a case of complete dominance. The genotype is Cca for both parents
♂/ ♀ | C | ca |
C | CC Chinchilla |
Cca Chinchilla |
ca | Cca Chinchilla |
caca Albino |
The cross (cross 6) between albino and Himalayan parents results in all Himalayan phenotype. This is also a case of complete dominance. The genotype is cchcch(female) and caca (male).
♂/ ♀ | cch | cch |
ca | cchca Himalayan |
cchca Himalayan |
ca | cchca Himalayan |
cacch Himalayan |
The cross (cross 7) between albino and chinchilla parents results in chinchilla and albino in 1:1 ratio. This is also a case of complete dominance. The genotype is Cca(female) and caca (male).
For cross 7:
♂/ ♀ | C | ca |
ca | Cca Chinchilla |
caca Albino |
ca | Cca Chinchilla |
caca Albino |
The cross (cross 8) between two albino parents results in all albino. This is also a case of complete dominance. The genotype of both parents is caca
♂/ ♀ | ca | ca |
ca | ca ca Albino |
ca ca Albino |
ca | ca ca Albino |
ca ca Albino |
The cross (cross 9) between himalayan and chinchilla parents results in chinchilla and chinchilla in 1:1 ratio. This is also a condition of complete dominance. The genotype of chinchilla parent is Ccch, and albino parent is cchcch or cchca.
♂/ ♀ | C | cch |
cch | C cch Chinchilla |
cch cch Himalayan |
cch | C cc Chinchilla |
cch cch Himalayan |
♂/ ♀ | C | cch |
cch | Ccch Chinchilla |
cchcch Chinchilla |
ca | Cca Chinchilla |
cchCa Himalayan |
The cross (cross 10) between Himalayan and chinchilla parents results in 2 chinchillas, 1 albino, and 1 Himalayan phenotype. The genotype of chinchilla parent is Cca and cchca.
For cross 10 :
♂/ ♀ | C | ca |
cch | Ccch Chinchilla |
cchca Himalayan |
ca | Cca Chinchilla |
ca ca Albino |
c.
To determine:
The progeny of chinchilla parents 9 and 10.
Introduction:
The dominant allele always expresses itself either homozygous or in heterozygous condition. The recessive allele is only expressed in homozygous condition, not in heterozygous condition.
Explanation of Solution
The cross between chinchilla 9 and 10 have gametes C and ca also C and cch. This cross results in chinchilla ¾ and Himalayan offsprings in ¼ ratio.
♂/ ♀ | C | cch |
C | CC Chinchilla |
cchC Chinchilla |
ca | C ca Chinchilla |
cchca Himalayan |
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