Final answer:
Down Syndrome is caused by a trisomy of chromosome 21, which is an abnormality in chromosome number. Klinefelter syndrome, resulting from an extra X chromosome in males (XXY genotype), is another example of a chromosomal number disorder identified through karyotype analysis. These disorders can have profound effects on health and development.
Step-by-step explanation:
A chromosomal abnormality where there is an extra chromosome 21, noted as 47,XX,+21 for females or 47,XY,+21 for males, is associated with Down Syndrome. This is an example of a genetic disorder caused by an abnormality in chromosome number, specifically a trisomy. In contrast, Klinefelter syndrome, which is characterized by a male having an additional X chromosome and an XXY genotype, results in underdeveloped sex organs and cognitive challenges.
Chromosome number disorders such as these arise from nondisjunction during meiosis. A karyotype analysis, which assesses the number, size, shape, and banding pattern of chromosomes, can reveal these and other chromosomal abnormalities, such as deletions, insertions, or translocations. Such disorders can have significant impacts on an individual's phenotype and health.