Molecular Genetics

Facts

Many non-mammalian vertebrates undergo parthenogenesis. In parthenogenesis, a complete new organism develops from a diploid female cell. Parthenogenesis is not known to occur in mammals. Microinjection of a mouse egg nucleus into a mouse egg leads to a non-viable embryo. Introduction of a mouse sperm nucleus into a mouse egg leads to an embryo that develops normally.

Interpretations

• The male-derived chromosome set must differ from the female. It must contain some markers needed for normal development.
• Some traits are known to be inerited non-Mendelianly from the male parent. This phenomenon is known as paternal imprinting.

Further information

• Paternal imprinting appears to occur only in mammals, raising the possibility that it evolved because of the parasitic-like relationship between mother and fetus.
• Maternal effects are also known. They result from deposition of molecules in the cytoplasm before fertilization.
• The mechanisms of imprinting are the subject of current research.

This is page 1381 of Molecular Genetics by Ulrich Melcher, © 1997, 1998, 1999, 2003