Final answer:
Two common syndromes caused by chromosomal abnormalities are Down syndrome and Klinefelter syndrome. Down syndrome is associated with an extra chromosome 21, while Klinefelter syndrome is characterized by a male having an additional X chromosome. Advanced parental age is a known risk factor for such abnormalities.
Step-by-step explanation:
There are two common syndromes caused by chromosome abnormalities, which are differences in the usual number or structure of chromosomes. These syndromes are Down syndrome and Klinefelter syndrome.
Down syndrome, also known as trisomy 21, occurs when there is an extra copy of chromosome 21. This results in a total of three copies of this chromosome, hence the term 'trisomy.' Down syndrome leads to characteristic physical features, developmental delays, and may include intellectual disability. It is often associated with nondisjunction during meiosis, a process where homologous chromosomes fail to separate properly. Parents' advanced age, especially maternal age, increases the risk of this disorder.
Klinefelter syndrome, on the other hand, affects males who inherit an extra X chromosome, resulting in an XXY genotype. Individuals with this syndrome may have underdeveloped sex organs, taller stature, reduced facial and body hair, and may experience learning difficulties.
Both Down syndrome and Klinefelter syndrome can be diagnosed through a karyogram, a visual profile of all the chromosomes in the nucleus of a cell. These syndromes illustrate how aberrations in chromosome number can have significant impacts on an individual's development and overall health.