(a) (i) What is the difference between the genotype and phenotype of an individual? (ii)...
(a) (i) What is the difference between the genotype and phenotype of an individual?
(ii) State two factors each which determine each of the terms in (a)(i).
(b) In a breeding experiment, a homozygous dog (BB) was crossed with a homozygous white dog (bb) to produce black puppies in the first filial generation (F1) The second filial generation produced a total of two hundred and forty (240) black and white puppies. With the aid of a genetic diagram, determine:
(i) the number of white puppies
(ii) the number of black puppies in the second filial generation.
Explanation
(a)(i) Difference between genotype and phenotype: A person's genotype is the sum total of the person's genetic constitution; while the phenotype is the observed trait/physical characteristics.
(ii) Factors which determine genotype: -
- Genotype of parents
- Mutation.
Factors which determine phenotype: -
- Genotype
- Environment;
- Diet
- Health.
Phenotypic ratio 3 black 1 white puppies
(b)Calculation: The number of white puppies using the phenotypic ratio
3 black: 1 white = 24
Total No of puppies produced = 240 .
No of white puppies produced = ¼ x 240 = 60 white puppies
(b)(ii) Number of black puppies = ¾ x 240 = 180 black puppies
OR calculation b(ii)
No of black puppies ¾ x 240 = 180
b(i) No of white puppies ¼ x 240 = 60