Cat Hair: White Is the Absence Of Pigment

For a cat and perhaps for other creatures white is the absence of pigmentation in the hair strands. The hair is not white because there is white pigmentation in the hair.  There is no pigmentation in the hair strands.  In short, white is the absence of colour in this instance whereas in an absolute sense white is the merging of all the colours of the visible spectrum. I think that's quite a nice contrast.

Natalie - a non-pedigree show cat. Photo copyright Helmi Flick.

You would have thought that if there is no pigmentation in each hair strand, each strand of hair would be transparent but clearly not.  Therefore, the un-pigmented hair strand must be white or opaque to a certain extent and very light in colour.

The reason why there is no pigment in the hair of white cats is because cells which are created very early on during the develop of the foetus inside the womb called melanoblasts - which turn into melanocytes (which are pigment producing cells) - do not migrate from their point of origin to the hair shaft.  The point of origin of melanoblasts is the trunk neural crest cells.

The reason why this migration does not take place is because of the white cat carries the white spotting gene or the dominant white gene.  In these cats the migration is partly or completely halted.

Because the cell in the skin in which the hair strand is embedded is unable to produce pigment (eumelanin and phaeomelanin) there is no pigment inside the hair strand; it looks white.

The white spotting gene is also called the piebald gene and it creates the bicolour cat (white and another color). These genes can cause deafness and odd-eye color.