In Down 's syndrome of a male child , the sex complement is

Options

A. XO
B. XY
C. XXY
D. XXY

Answer

To determine the sex complement of a male child with Down syndrome, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Down Syndrome**: Down syndrome, also known as Trisomy 21, is a genetic disorder caused by the presence of an extra copy of chromosome 21. This results in a total of 47 chromosomes instead of the typical 46.

2. **Identify the Sex Chromosomes**: In humans, males typically have one X and one Y chromosome (XY). This combination determines male sex characteristics.

3. **Determine the Chromosomal Composition**: In the case of a male child with Down syndrome, the individual will have the typical male sex chromosomes (XY) along with the extra chromosome 21. Therefore, the chromosomal composition would be 47 chromosomes: 46 (XX or XY) plus the additional chromosome 21.

4. **Conclude the Sex Complement**: Since the individual is male, the sex complement remains XY despite the presence of the extra chromosome 21. Thus, the sex complement for a male child with Down syndrome is XY.

5. **Final Answer**: The sex complement of a male child with Down syndrome is XY.