An abnormal diploid egg is fertilised by a normal haploid sperm. What is the zygote?

1. A normal egg is haploid and carries one set of chromosomes. 2. The abnormal egg described here is diploid, so it carries two sets. 3. The sperm is normal and haploid, contributing one set. 4. Fertilisation adds the sets together: two from the egg plus one from the sperm. 5. Three complete sets makes the zygote triploid. 6. Carrying more than the correct number of sets makes it polyploid rather than aneuploid. 7. Tetraploid would need four sets, which would require both gametes to be abnormal. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 13 "Modern Understandings of Inheritance", section 13.2 Chromosomal Basis of Inherited Disorders_