An organism has a gene ' X '. Its dominant allele expresses character c - 1 while it's recessive allele expresses character c - 2 This dominant allele is completely dominant over the recessive allele . It has another gene ' y ' which in its dominant form doesn't allow any expression of gene ' x ' which of these genotypes of that organism Will produce character c - 1 ?

Options

A. xxyy or XxYy
B. XXYY or xxyy
C. xxYy or XXYy
D. Xxyy or Xxyy

Answer

To solve the problem, we need to analyze the information provided about the genes and their alleles.

### Step-by-Step Solution:

1. **Understanding Gene X**:
- Gene X has two alleles:
- Dominant allele (X) expresses character C1.
- Recessive allele (x) expresses character C2.
- The dominant allele (X) completely masks the expression of the recessive allele (x).

2. **Understanding Gene Y**:
- Gene Y also has two alleles:
- Dominant allele (Y) does not allow the expression of gene X.
- Recessive allele (y) allows gene X to express.
- Therefore, if the organism has at least one dominant Y allele (Y), gene X will not be expressed regardless of the alleles of gene X.

3. **Identifying Conditions for C1 Expression**:
- For character C1 to be expressed, the organism must have at least one dominant allele of gene X (X).
- Additionally, the organism must not have the dominant allele of gene Y (Y) present, as it would inhibit the expression of gene X.

4. **Analyzing Possible Genotypes**:
- We need to evaluate the given genotypes to see which one meets the conditions for expressing C1.

- **Option A**: xx yy
- This genotype has two recessive alleles for both genes.
- Result: C2 is expressed (not C1). **(Incorrect)**

- **Option B**: XY
- This genotype has one dominant allele of Y.
- Result: C1 is not expressed due to the presence of Y. **(Incorrect)**

- **Option C**: XX YY
- This genotype has two dominant alleles of Y.
- Result: C1 is not expressed due to the presence of Y. **(Incorrect)**

- **Option D**: Xy
- This genotype has one dominant allele of X and one recessive allele of Y.
- Result: C1 is expressed because Y is recessive and does not inhibit gene X. **(Correct)**

5. **Conclusion**:
- The only genotype that allows for the expression of character C1 is **Option D: Xy**.