Down's syndrome is an example of
(A) incomplete dominance
(B) genetic engineering
(C) a chromosome disorder
(D) a sex-linked disorder

Answer

**Step-by-Step Solution:**

1. **Understanding Down's Syndrome**:
- Down's syndrome is a genetic condition that is caused by the presence of an extra chromosome 21. This condition is also known as Trisomy 21.

2. **Identifying the Type of Disorder**:
- Down's syndrome is classified as a chromosomal disorder because it involves a change in the number of chromosomes in an individual. Normally, humans have 46 chromosomes, but individuals with Down's syndrome have 47 due to the extra chromosome.

3. **Eliminating Other Options**:
- (A) Incomplete dominance refers to a genetic scenario where neither allele is completely dominant, resulting in a blend of traits. This does not apply to Down's syndrome.
- (B) Genetic engineering involves modifying the genetic makeup of an organism, which is not relevant to Down's syndrome.
- (D) A sex-linked disorder is one that is associated with genes located on sex chromosomes (X or Y). Down's syndrome is not linked to sex chromosomes.

4. **Conclusion**:
- Since Down's syndrome is caused by an abnormal number of chromosomes (specifically, an extra chromosome 21), it is classified as a chromosome disorder.

**Final Answer**: (C) a chromosome disorder.

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