Question 3:
In a type of cattle, white face and long horns are dominant traits as opposed to those with black face and short horns as shown in Photograph 1. A breeder plans to breed all white face and long horns cattle in his farm. Prior to that, he has to ensure that his bull and cow are purebreed. As a geneticist, explain how you can assist the breeder in determining whether his cattle is purebreed or hybrid?
Answer:
• If W represents dominant allele for white face, w represents recessive allele for black face and L represents dominant allele for long horns and l represents recessive allele for short horns.
• White face and long horns phenotype will have W_L_ genotype.
• Purebreed parent genotype for white face and long horns is WWLL.
• To obtain purebreed progeny, the progeny has to receive similar genes from both parents.
• To know the parental genotype, it has to be mated with a cattle with purebreed homozygous recessive genotype which has a black face and short horns (wwll).
• Mating : W_L_ x wwll
F1 generation
F1 generation that is produced enable us to determine the parental genotypes.
• Mating 1
If parent is purebreed (WWLL), mating with purebreed homozygous recessive will produce all progenies in F1 generation which have white face and long horns.
• Mating 2
WWLl x wwll produces progenies with WwLl genotype (white face and long horns) and Wwll (white face and short horns)
• Mating 3
WwLL x wwll produces progenies with WwLl genotype (white face and long horns) and wwLl (black face and long horns)
• Mating 4
WwLl x wwll produces progenies with WwLl genotype (white face and long horns), Wwll (white face and short horns), wwLl (black face and long horns) and wwll (black face and short horns)
• Therefore, based on the mating outcomes, the breeder cannot use mating approaches 2, 3 and 4 because those mating approaches produce many types of progeny phenotypes.
• The most suitable approach to obtain all progenies with white face and long horns is to follow mating approach 1 because mating outcomes show that the parent is purebreed.
In a type of cattle, white face and long horns are dominant traits as opposed to those with black face and short horns as shown in Photograph 1. A breeder plans to breed all white face and long horns cattle in his farm. Prior to that, he has to ensure that his bull and cow are purebreed. As a geneticist, explain how you can assist the breeder in determining whether his cattle is purebreed or hybrid?
Answer:
• If W represents dominant allele for white face, w represents recessive allele for black face and L represents dominant allele for long horns and l represents recessive allele for short horns.
• White face and long horns phenotype will have W_L_ genotype.
• Purebreed parent genotype for white face and long horns is WWLL.
• To obtain purebreed progeny, the progeny has to receive similar genes from both parents.
• To know the parental genotype, it has to be mated with a cattle with purebreed homozygous recessive genotype which has a black face and short horns (wwll).
• Mating : W_L_ x wwll
F1 generation
F1 generation that is produced enable us to determine the parental genotypes.
• Mating 1
If parent is purebreed (WWLL), mating with purebreed homozygous recessive will produce all progenies in F1 generation which have white face and long horns.
• Mating 2
WWLl x wwll produces progenies with WwLl genotype (white face and long horns) and Wwll (white face and short horns)
• Mating 3
WwLL x wwll produces progenies with WwLl genotype (white face and long horns) and wwLl (black face and long horns)
• Mating 4
WwLl x wwll produces progenies with WwLl genotype (white face and long horns), Wwll (white face and short horns), wwLl (black face and long horns) and wwll (black face and short horns)
• Therefore, based on the mating outcomes, the breeder cannot use mating approaches 2, 3 and 4 because those mating approaches produce many types of progeny phenotypes.
• The most suitable approach to obtain all progenies with white face and long horns is to follow mating approach 1 because mating outcomes show that the parent is purebreed.