Which are the causes of Triploidy?

Triploidy is a genetic disorder characterized by the presence of an extra set of chromosomes in an individual's cells. Instead of the usual two sets of chromosomes (one from each parent), triploid individuals have three sets, resulting in a total of 69 chromosomes instead of the normal 46. This condition can occur in both humans and animals, and it is typically associated with severe developmental abnormalities and health issues.

The causes of triploidy can be classified into two main categories: diandry and digyny. Diandry refers to the fertilization of an egg by two sperm cells, resulting in a triploid zygote. Digyny, on the other hand, occurs when a diploid egg is fertilized by a haploid sperm, leading to triploidy.

Diandry: Diandric triploidy is less common than digynic triploidy and accounts for approximately 20% of triploid cases. It usually arises from one of the following mechanisms:

• Dispermy: This occurs when two sperm cells fertilize a single egg simultaneously. It can happen due to abnormal events during fertilization, such as delayed release of the second polar body or failure of the egg to complete meiosis.


• Endoreduplication: In some cases, a single sperm cell may fuse with an egg that has undergone abnormal replication, resulting in a triploid zygote.

Digyny: Digynic triploidy is the most common form of triploidy, accounting for approximately 80% of cases. It can occur due to various mechanisms, including:

• Non-disjunction: Non-disjunction refers to the failure of chromosomes to separate properly during meiosis. In digynic triploidy, this can occur in the egg, leading to the presence of an extra set of chromosomes.


• Polyspermy: Polyspermy happens when multiple sperm cells fertilize a single egg. This can result in the formation of a triploid zygote.

Other causes: In addition to diandry and digyny, triploidy can also arise from other rare causes, such as errors during cell division after fertilization or errors in the replication of chromosomes during early embryonic development.

Consequences of triploidy: Triploidy is associated with severe developmental abnormalities and health issues. Most triploid pregnancies end in miscarriage, and those that survive to term often have multiple congenital anomalies, such as heart defects, brain abnormalities, and growth retardation. The prognosis for individuals with triploidy is generally poor, and they often have a significantly shortened lifespan.