The diagnosis of Down syndrome is made by examining the individual's -

Options

A. Spores
B. Kariotype
C. Chromatin
D. Nucleosome

Answer

To answer the question about how the diagnosis of Down syndrome is made, we can break down the solution into the following steps:

### Step 1: Understanding Down Syndrome
Down syndrome, also known as Trisomy 21, is a genetic disorder caused by the presence of an extra chromosome 21. This condition results in a total of three copies of chromosome 21 instead of the usual two.

### Step 2: Karyotyping
The diagnosis of Down syndrome is primarily made through a process called karyotyping. Karyotyping involves the examination of an individual's chromosomes. This is done by taking a sample of cells (often from blood) and staining the chromosomes to visualize them under a microscope.

### Step 3: Arranging Chromosomes
In karyotyping, chromosomes are arranged in pairs based on their length and the position of the centromere (the central part of the chromosome). This arrangement allows for a clear view of the number and structure of chromosomes.

### Step 4: Identifying Trisomy 21
During karyotyping, the chromosomes are counted and analyzed. In a normal human karyotype, there are 46 chromosomes (23 pairs). However, in individuals with Down syndrome, there will be 47 chromosomes due to the extra chromosome 21. This condition is referred to as "2N + 1," where "N" represents the normal diploid number of chromosomes.

### Step 5: Conclusion
Thus, the diagnosis of Down syndrome is made by examining the individual's karyotype, specifically looking for the presence of an extra chromosome 21.

### Final Answer
The diagnosis of Down syndrome is made by examining the individual's **karyotype**.

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