What is a common chromosomal configuration that leads to triploidy?

Triploidy is a chromosomal condition where an individual has three sets of chromosomes, totaling 69 chromosomes instead of the usual 46. A common configuration that leads to triploidy occurs when an egg is fertilized by two sperm, a situation known as dispermic fertilization. This results in the zygote receiving two sets of paternal chromosomes and one set of maternal chromosomes.

In this scenario, the typical diploid set of chromosomes that results from a single egg and single sperm fertilization is altered. When only one egg is fertilized by two sperm, the additional genetic material from the second sperm contributes to the total number of chromosomes, leading to the triploid state. Understanding this mechanism is crucial for genetic counselors, as triploidy can have distinct clinical implications and outcomes in prenatal settings.

The other configurations, while they may involve unusual fertilization scenarios, either do not lead to triploidy or describe less common situations resulting in different chromosomal abnormalities.