Cat genetics

Every time a new pregnant mama or litter of kittens comes in to TinyKittens, speculation begins about baby daddy colours and patterns, which leads to discussions about feline genetics. I thought I’d share a list of some of my favourite feline genetic sites and resources. If you have any resources you think should be added or if you have any information that should be added or corrected, just leave a comment at the bottom of this (or any) page.

Cat Genetics in a Nutshell:

Calico vs tortie

Tortoiseshell cats (which as a group includes torties and calicos and their variants) have coats that contain a mix of black and orange, plus possibly white. They are almost always female, as black and orange are carried on the X chromosome — as the kitten is forming in utero, one or other of her two X chromosomes turns on; if dad is ginger and mom is black, then her fur becomes black where mom’s X chromosome turns on and ginger where dad’s does, resulting in a tortie/calico pattern. The more white the cat has, the bigger and more differentiated the patches of colour are, with full tortie at one end (with no white at all) and mostly white calico at the other end. The line between them blurs towards the middle of the spectrum.

First, there are the straight up torties and calicos:

• Tortie:  Mix of  small, generally not discrete patches of black and orange, with possibly small amounts of white. (Shiloh is a good example of a tortie with very little or no white; most of her colour patches are very small, mixed, and not very differentiated. Sable is also a very good example of a dark-heavy tortie.)
• Calico: Calicos have larger, more discrete patches of colour than torties. The more white they have, the more distinct their colour patches are. (Scout is one of the few non-tabby calicos at the colony.)

Then there are the torties and calicos that also have a tabby pattern:

• Torbie: Tortie + Tabby. Essentially a tortie, where either the black or the orange (or both) displays the tabby pattern as well.
• Caliby: Calico + Tabby. Essentially a calico, where either the black or the orange (or both) displays the tabby pattern as well. (Skye and Sloane are both examples of a caliby, as their ginger bits are tabby.)

Then the patterns in that blurring area in the middle of the tortie/calico spectrum:

• Tortico: Tortie + Calico. This is where that line between tortie and calico really blurs, where the pattern is a mix of fairly discrete patches of colour (without tabby markings) and the indistinct colour mixing of tortoiseshell.
• Torbico: Tortie + Calico + Tabby. This is where that line between torbie and caliby blurs, where the pattern is a mix of fairly discrete patches of colour (with tabby markings) and the indistinct colour mixing of tortoiseshell. (Serenity is what I would consider to be an example of this — she has some fairly large patches of a single tabby colour but also large patches of tortie/torbie. Sierra is also an example, as she had some larger discrete patches of black and ginger tabby plus white. Most of the “torbies” at the colony are what I would actually call “torbicos”.)

Red (or orange) and black

Red (or orange) and black are both dominant colors. Dominant traits don’t skip a generation so one of the parents must exhibit a dominant colour for the kitten to get it. Because colour is carried on the X chromosome, male kittens can only get their colouring from their mother while girls can get their colouring from both mom or dad (pattern depends on which parent’s X chromosome is activated in the cells in any given patch of fur). So if you have a ginger mom and a black dad, boy kittens will be ginger (with or without tabby markings) and girl kittens will be some form of tortie or calico (with or without tabby markings).

Tabby patterns

• Classic or blotched: This pattern is swirly, sometimes with a bullseye pattern on the side. (Stanley, from the Bradner colony, has a classic tabby pattern.)
• Mackerel or striped: This pattern consists of long stripes that often look like a fish skeleton. (Hannity aka Hanna Tea is a mackerel tabby.)
• Spotted: This is a pattern where mackerel stripes are broken up into spots. (Maravel is an example of a spotted tabby.)
• Ticked:  The ticked hairs in this pattern contain bands of colour, resulting in a sort of salt and pepper or speckly appearance (sometimes with faint striping), rather than the distinct striping or swirling of the other patterns. (Zetta is an example of a ticked tabby.)

Dilution

Dilute is a term that can be applied to any colour. Dilute black is grey, dilute orange is a buff colour. (Starling is an example of a dilute calico, where both her dark and orange patches are lighter, grey and buff instead of black and orange; she does not have any tabby. Tiger Buffy is an example of a dilute ginger tabby.)

Examples from TinyKittens fostering history

• The Roundup Kittens: TeeKay (ginger) and Chef (tortie) were daughters of Athena (tortie). TeeKay’s father would have been a ginger; Chef’s could have been the same ginger or could have been pretty much any other colour. Ginger TeeKay’s three babies (two boys, Shepherd and Coulter, and a girl, Moose) were all ginger as well — the boys’ father could have been anything, but Moose’s father must have been ginger as well.
• Sisko was tortie. Her final litter consisted of one tortie girl (Bluebelle), one ginger girl (Daisy), four black boys (Toothless, Walt, Bambi, and Thumper), and two black girls (Owl and Flower). Bluebelle’s father could have been any colour, and Daisy’s father must have been ginger for her to be ginger — we know from DNA testing that they (and Walt) have the same father, who then must have been ginger. The colour of the black boys father is irrelevant as they would have gotten their colour from Sisko. Owl’s father and Flower’s father (we know from DNA testing that they don’t have the same father) would have been black in order for them to be black.
• Lorelai: Lorelai is black with little bits of white. Her daughter Rory is a mini-me. Depending on the colour of the father(s), Lorelai’s kittens could have been black (with or without white), tortie or calico (with or without white, with or without tabby), or straight-up tabby (with or without white). In reality, she had three tabby girls, one black girl, and one black boy.

Resources

Sites and Articles

• ♥♥ Wikipedia: Cat Genetics is a good starting point for information about feline genetics, including a really good series of pages about the genetics of various coat colours.
• ♥♥ Sarah Hartwell’s MessyBeast site offers a huge amount of cat-related information, including a number of pages and charts devoted to the genetics of coat colours, patterns, eyes, ears, tails, etc.
• ♥♥ Joumana Medlej has created some great infographics about cat coat colors, patterns, and breeds characteristics. You can view her “Guide to Housecat Colors and Patterns” graphic online on her site. (You can also buy all of her cat-related guides in book or e-book format; this book includes her guides to large and small wild cats in addition to her housecat guides.) The infographics are primarily for artists, but offer excellent information about coat patterns, including pattern and colour terminology. You can buy poster versions of this graphic and her others through Redbubble for a pretty reasonable price, especially if you catch one of the many Redbubble sales that occur throughout the year. (I personally have two copies of these posters myself, a set of the small ones that I keep folded up with my decidedly amateur/aficionado veterinary notes and a set of the medium ones that used to be on my bedroom wall.)
  • Guide to Housecat Coat Colors and Patterns 
    
  • Housecat Breeds part 1 and part 2
     
• Basic Genetics as Revealed by Cats — Lecture handout from the UC Berkley Department of Integrative Biology course “IB162: Ecological Genetics” about the basic genetics of cat coat colour and pattern.
• Cat Coats and Genes: Closer to the origin of Tabby cats’ stripes — Article from the Tech Museum of Innovation (a project of the Department of Genetics, Stanford School of Medicine) that explores the genetics behind tabby coat patterns (classic or blotched versus mackerel or striped versus spotted).
• Calico Cats Are A Walking Genetics Lesson — Article from the American Council on Science and Health that briefly explores the genetics behind the expression of ginger and black in the coat of a calico.
• Basic Feline Genetics — This article from the Cat Fanciers Associations offered a list of notes regarding how dominant and non-dominant traits (coat colour, eye colour, etc.) will be passed down through breeding.
• The Genetics of Calico Cats — This article provides a brief explanation for how the calico or tortoiseshell coat patterns come into play genetically.
• Tenset: Cat Coat Color Genetics — Offers background information about the genetics behind cat coat colours.
• 7 Genes That Control Your Cat’s Fur Color — Catster article giving a nice, quick overview of the basics of the seven main genes responsible for the colour of a cat’s fur: black (B/b/b’), agouti (A/a), tabby (T/Ta/tb), dense/dilute (D/d), orange (O/o), spotting (S/s), and white (W/w). The article includes a link to an “interview” between the author’s ginger female cat and a biologist about cat fur genetics.

Books

• Robinson’s Genetics for Cat Breeders and Veterinarians by Carolyn Vella, John McGonagle, Lorraine M. Shelton, and Terry W. Stanglein — You can generally buy this book from any online retailer like Amazon or Better World Books; it’s pretty pricey but within the typical textbook range of things. The latest edition is the 4th edition, published in 1999 by Elsevier. (Elsevier, unfortunately, doesn’t have a valid page for purchasing this book from them directly.)
• Genetics for Cat Breeders by Roy Robinson — You can generally buy this book from online retailers like Amazon or Better World Books. You can also purchase a DRM-free PDF version from Elsevier. (You can often find a cheap used copy on Better World Books for a lot less than Amazon or Elsevier. My copy cost about $12 US in 2017.)
• Cats Are Not Peas: A Calico History of Genetics by Laura Gould — Second edition published in 2008; first edition published in 1992. The book is generally available from online retailers like Amazon and Better World Books. The second edition tends to be fairly expensive, but used copies of the first edition can usually be found for less than $10 US. (You get what you pay for, though — the second edition includes a 50-page addendum that is not in the earlier edition.)
• Cat Sense: How the New Feline Science Can Make You a Better Friend to Your Pet by John Bradshaw —  While I don’t necessarily agree with everything in this book, John Bradshaw does offer some interesting background on the science behind what makes cats cats. It’s available to borrow in physical and digital format from the Fraser Valley Regional Library. It’s also available to purchase in physical and digital format from bookstores, including Amazon.

Videos

• Blue Collar Den‘s cat genetics video series on YouTube — This series of videos seems to be aimed mostly at kids, but the videos are still quite informative and worth a watch. (Note: The Warrors Special video really just picks apart the lack of accurate genetics in the Warriors book series, so you may want to just skip that one.)
  
  #1 – Solids and Tortoiseshells  — #1.5 – Red Gene Corrections — #2 – White — #3 – Tabbies
  #4 – Colourpoints — #5 – The Silver Gene — #6 – Warriors Special  — #7 – Other Colours