the believe they move inside the membrane which is creating a gradient
The first one, is :
Embryology - The branch of biology and medicine concerned with the study of embryos and their development.
The second one is:
Vestial Traits - An anatomical feature or behavior that no longer seems to have a purpose in the current form of an organism of the given species.
Codominance.
Because in the codominance, both the traits of the brown hair and white hair is expressed. So it carries both the traits, regardless of whether it is recessive or dominant.
Hope this helps :)