Mark correct option w.r.t multiple alleles.

Options

A. Show crossing over between them
B. Are always codominants
C. Affect different characters
D. Are found in population

Answer

### Step-by-Step Solution:

1. **Understanding Multiple Alleles**:
- Multiple alleles refer to a situation where a single gene has more than two alternative forms (alleles). This is different from the typical scenario where a gene has only two alleles (dominant and recessive).

2. **Identifying Characteristics of Multiple Alleles**:
- Multiple alleles exist at the same locus on homologous chromosomes. This means that they are located at the same position on a pair of chromosomes.

3. **Evaluating the Given Options**:
- **Option 1**: "Show crossing over between them" - This is incorrect. Crossing over occurs between homologous chromosomes, but multiple alleles are different forms of the same gene at the same locus, so they do not cross over.
- **Option 2**: "Are always co-dominant" - This is also incorrect. While some multiple alleles can exhibit co-dominance, not all do; dominance relationships can vary among the alleles.
- **Option 3**: "Affect different characters" - This is incorrect. Multiple alleles refer to different forms of the same gene, which affects the same character (trait).
- **Option 4**: "Are found in population" - This is correct. Multiple alleles can only be observed in a population, as they represent variations of a single gene.

4. **Conclusion**:
- The correct option regarding multiple alleles is **Option 4**: "Are found in population".