Who says you need an egg to create an embryo?

PARIS: We all grow up to accept certain unassailable facts: water is wet, the Earth is round, and to produce a baby you need an egg and sperm.
As it turns out, the last of these may turn out not to be true.
On Tuesday, scientists announced they had produced baby mice by fusing sperm and a type of cell that is not an egg. The pups that survived this alchemy were healthy, with normal life spans, and able to procreate the traditional way, researchers from Britain and Germany reported in the journal Nature Communications.
“It had been thought that only an egg cell was capable of reprogramming sperm to allow embryonic development to take place,” said the report’s senior author Tony Perry of the University of Bath.
“Our work challenges the dogma, held since early embryologists first observed mammalian eggs around 1827 and observed fertilization 50 years later, that only an egg cell fertilized with a sperm cell can result in a live mammalian birth.”
There are two types of cell: “meiotic” reproductive cells (eggs and sperm), and “mitotic” cells which include most of the tissues and organs in our bodies. Mammal reproduction requires a sperm and egg to fuse, creating an embryo.
But instead of using a meiotic egg cell to produce their mouse pups, the researchers used a type of mitotic cell called a parthenogenote.
These are very early-stage, single-celled embryos that form without fertilization — in this case by chemically activating a mouse egg.