What is the percentage of each genotypic and phenotypic if a black individual is crossed with a bluish-gray individual ?
The correct answer and explanation is :
To determine the genotypic and phenotypic percentages when a black individual is crossed with a bluish-gray individual, we need to analyze the inheritance pattern.
Assumptions:
- Coat Color Inheritance: In many animals, including livestock and dogs, black (B) is often dominant over dilute colors such as bluish-gray (b), which is recessive.
- Genotypes:
- A black individual could be BB (homozygous dominant) or Bb (heterozygous).
- A bluish-gray individual must be bb (homozygous recessive) because the recessive trait only appears when two recessive alleles are present.
Possible Crosses and Outcomes:
Case 1: If the black parent is BB (homozygous dominant)
- Cross: BB × bb
- Punnett Square: B B b Bb Bb b Bb Bb
- Genotypic Ratio: 100% Bb (heterozygous)
- Phenotypic Ratio: 100% Black (since Bb shows the dominant black trait)
Case 2: If the black parent is Bb (heterozygous)
- Cross: Bb × bb
- Punnett Square: B b b Bb bb b Bb bb
- Genotypic Ratio:
- 50% Bb (heterozygous, black)
- 50% bb (homozygous recessive, bluish-gray)
- Phenotypic Ratio:
- 50% Black
- 50% Bluish-gray
Final Answer:
- If the black parent is BB, the offspring will be 100% Black.
- If the black parent is Bb, the offspring will be 50% Black and 50% Bluish-gray.
Explanation:
The inheritance of coat color follows Mendelian genetics, where a dominant allele (B) masks the effect of the recessive allele (b). If the black individual is homozygous (BB), all offspring inherit at least one dominant B allele, making them black. However, if the black individual is heterozygous (Bb), there is a 50% chance of passing the recessive b allele, resulting in some bluish-gray offspring. Understanding genetics helps in predicting offspring traits, which is useful in animal breeding and conservation genetics.