Final answer:
Edward's syndrome, known as Trisomy 18, involves having a surplus chromosome 18, leading to developmental delays and health complications. It is detected by karyotyping and is less common than Trisomy 21 (Down syndrome), which can also be linked to an increase in maternal age. Such chromosomal disorders highlight the importance of balanced gene dosage for human development.
Step-by-step explanation:
Understanding Edward's Syndrome (Trisomy 18)
Edward's syndrome, also known as Trisomy 18, is a chromosomal condition characterized by an extra copy of chromosome 18, resulting in a total of 47 chromosomes in each cell, instead of the usual 46. This condition is caused by a chromosomal nondisjunction during meiosis. To diagnose Edward's syndrome, a karyotype can be used to reveal the number and structure of chromosomes in an individual. While Trisomy 18 is a severe genetic disorder, it is not as common as Down syndrome, also known as Trisomy 21, which is the most prevalent trisomy condition that can lead to adulthood for some affected individuals. Edward's syndrome leads to serious developmental delays along with a range of health complications, and survival beyond infancy is rare.
Trisomies are generally rare, but the likelihood of bearing a child with Down syndrome, the most common form of trisomy, increases with the maternal age, especially in women over the age of 36. This is attributed to the increase in the frequency of chromosomal nondisjunction as the oocytes age.
Aneuploidy and Gene Dosage
Aneuploidy refers to the condition of having a non-standard number of chromosomes, which includes both monosomy and trisomy. The presence of an extra chromosome in conditions like Edward's syndrome results in an imbalance, leading to an excessive quantity of certain gene products. This imbalance severely impacts development and overall health. Most autosomal trisomies are incompatible with life, leading to miscarriage, but some, including chromosomes 13, 15, 18, 21, and 22, can lead to live births, albeit with associated severe medical and developmental challenges.