A comparison of the karyotypes of a normal human male and a male sufferer of Down's syndrome shows the latter to possess

Options

A. one extra chromosome
B. two Y chromosomes
C. one extra pair of chromosomes
D. twice the normal number of chromosomes

Answer

### Step-by-Step Solution:

1. **Understanding Karyotypes**: A karyotype is a visual representation of an individual's chromosomes. In humans, a normal male has a total of 46 chromosomes, arranged in 23 pairs.

2. **Normal Male Karyotype**: In a normal human male, the karyotype will show 22 pairs of autosomes and one pair of sex chromosomes (XY).

3. **Down Syndrome Overview**: Down syndrome, also known as Trisomy 21, is a genetic disorder caused by the presence of an extra copy of chromosome 21.

4. **Karyotype of Down Syndrome**: In the case of a male with Down syndrome, the karyotype will show 47 chromosomes in total. This includes the usual 22 pairs of autosomes and one additional chromosome 21, resulting in three copies of chromosome 21 instead of the normal two.

5. **Comparison**: Therefore, when comparing the karyotypes of a normal male and a male with Down syndrome, the key difference is that the male with Down syndrome has one extra chromosome, specifically an extra chromosome 21.

6. **Conclusion**: The answer to the question is that the male sufferer of Down syndrome possesses one extra chromosome (chromosome 21).