Thanks Karen! Melanistic is caused by the non agouti gene...let me explain...
Many savannahs and cats in general have alternating bands of black and yellow along the hair shaft - this is known as Agouti (ticking)...the gene responsible for the banding is called Agouti Signaling Protein or ASIP...
A DNA change, or mutation in the ASIP gene can significantly affect the fur pattern in cats. In its homozygous form, which means the cat carries two copies of this DNA change (aa), the result is black pigment along the entire shaft of hair and the coat of the cat is then “solid” in color or int he case of some breeds, ghost spotting occurs, meaning you can see spotting in the light, unless, like Siri as a kitten, the spotting is more visible!
The normal banding by the Agouti gene is dominant in terms of inheritance, meaning the banding pattern will result if a cat carries either one (Aa) or two copies (AA) of the normal Agouti gene. Therefore, AA or Aa cats cannot be distinguished by look. Only a DNA test can prove which cat is a carrier of non-Agouti. So Zuri, Siri's mother is Aa...she carries one copy of the non Agouti gene...when bred to another Aa cat, she will likely have one or more melanistic kittens...when bred to an AA cat, she will have no Melanistic kittens...
Siri is aa...bred to an Aa cat, she will likely have 50% Melanistic kittens...bred to an AA cat, no Melanistic kittens and an aa cat, all melanistic kittens...
In many cats the banded, agouti fur alternates with solid color fur in some sort of pattern, which is called tabbying - savannahs are tabbies...An “aa” form of the gene will hide the “tabby” pattern.
Hope this helps and did not confuse you...I am fascinated by genetics...my females are both DNA tested, which is why I can tell you exactly what they carry for
