Define the terms triploidy and autosomal trisomy and describe characteristics and consequences of ...

The most common form of polyploidy in humans is triploidy. Triploidy occurs when the chromosomal number is three times the haploid number. Triploid newborns have multiple abnormalities, including an enlarged head fused fingers and toes, and malformations of the mouth, eyes, and genitals. The high rate of embryonic death and failure to survive after birth indicates that triploidy is a lethal condition. Most autosomal trisomies, a type of aneuploidy usually caused by nondisjunction, are lethal during prenatal development and account for up to 50 of the chromosomal abnormalities seen in miscarriages. Only a few autosomal trisomies result in live births. Down syndrome, trisomy 21, is the only autosomal trisomy that allows survival into adulthood.