To determine the most likely genotypes of the parents based on the given data, let's analyze the inheritance pattern of fur color in mice.
The data provided is:
- 22 mice with black fur
- 23 mice with white fur
- Total of 45 mice
### Step 1: Understanding the Genotype and Phenotype Relationship
- Assume the fur color trait is controlled by a single gene with two alleles: F (dominant allele for black fur) and f (recessive allele for white fur).
- Black fur can result from either FF (homozygous dominant) or Ff (heterozygous).
- White fur results from ff (homozygous recessive) only.
### Step 2: Analyze the Ratio
The numbers of black and white fur mice are nearly equal, about a 1:1 ratio (22 black to 23 white).
### Step 3: Evaluate Possible Parental Genotype Combinations
#### Option A: FF (black) × ff (white)
- All offspring would be Ff (black). This option would produce 100% black fur offspring and 0% white fur offspring, inconsistent with the data.
#### Option B: FF (black) × Ff (black)
- This combination would yield:
- 50% FF (black)
- 50% Ff (black)
- Resulting in 100% black fur and 0% white fur, inconsistent with the data.
#### Option C: Ff (black) × Ff (black)
- This combination would yield a classic Mendelian 3:1 ratio:
- 25% FF (black)
- 50% Ff (black)
- 25% ff (white)
- However, since Ff and FF both display black fur, the phenotypic ratio observed would be 75% black to 25% white in large samples.
- Important: In smaller samples or specific cases such as 45 offspring, approximate ratios can vary due to statistical fluctuation. An approximate 1:1 ratio here suggests that random distribution has slightly deviated from theoretical expectation but still supports Ff x Ff.
#### Option D: Ff (black) × ff (white)
- This combination would yield:
- 50% Ff (black)
- 50% ff (white)
- This results in a 1:1 ratio of black to white fur, closely matching the observed data.
### Step 4: Conclusion
Given the nearly 1:1 ratio of black to white fur mice, the most likely genotype of the parents is indeed that which typically produces this ratio. This supports the combination:
- Option C: Ff and Ff
Thus, the most likely genotypes of the parents are:
Ff and Ff (Option C).
