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Color genetics

post #1 of 18
Thread Starter 
I just want to check if I am thinking right here:

I have a girl - black smoke tortoiseshell with white (Norwegian Forest Cat). Her mother is black silver tabby and the father is red with white.

She has one brother who is black and one who is black silver tabby like his mother. BUT she also has a sister who is black silver tabby! As to my knowledge - if you mate a black queen to a red male, all the female kittens must be tortoiseshell to some degree. So I think this black silver tabby girl is really a tortoiseshell genotype, but with so little red that it does not show (fenotype).

Is this correct or have I got my genetics totally wrong here?
post #2 of 18
I am not a geneticist by any means but from my 2yr college major ..lol..

red and white are ressesive ... so it is likely your girl has a gene or two( ultra simplified) that could make a red or black tortie... since yours has white she may not have a red gene... so kinda correct
post #3 of 18
here is my easy way of showing..

X will be black
Y will be white
x will be red
y will be silver

so dad is Xy and mom is Yx and they can produce in a litter of 4 XY Xx Yy Xy xy

XY is black with some white possible
Xx is black
Yy is likely silver or gray
xy is likely silver with red highlights///
post #4 of 18
Thread Starter 
I may have expressed myself very unclear. I was not asking about my cat - she is a black smoke tortie with white. It was about her sister (fenotype: black silver tabby) who in my opinion must be a tortie genotype.

By the way, red is not recessive - the red color is on the X chromosome (the female one) and will always give red boys and tortie girls if a red queen is mated with a black male, because the X in the baby boys XY will always be red. A black female mated with a red male will never give red boys, but she will have tortie girls. This particular female kitten shows no red - that is my question.

(Hope I got this the right way, it is so easy to get mixed up here)
post #5 of 18
Thread Starter 
#3 Today, 07:50 PM
Super Cat Join Date: Jan 2005
Posts: 1,159

here is my easy way of showing..

X will be black
Y will be white
x will be red
y will be silver

so dad is Xy and mom is Yx and they can produce in a litter of 4 XY Xx Yy Xy xy

XY is black with some white possible
Xx is black
Yy is likely silver or gray
xy is likely silver with red highlights///
Sorry, I do not quite understand that. Let's forget about the white and silver here. The question is about black and red, really:

Black female mates red male
My genetics book says that the kitten must be:
Black boys
Tortie girls

Nothing else! But this girl I am talking about is black (fenotype - meaning that is what you can see), so I figure she must be a tortie underneath (genotype - in the genes, but you cannot see it)
post #6 of 18
lol.. i am sorry sometimes i write clear as mud...

red is ressesive in humans and cats ( ie why there arent as many red girls as red boys)

the tortie is where i have a problem not knowing how it would affect ...

so for simplfication...

X is black

Y is red

if cat in ?? is a true black it would be XX , if it appears to be black but has a red gene underlying ...XY

so say there is a true black XX mates with a tortie XY

baby a will be XX
baby b will be XY
baby c will be XX
baby d will be XY

all will be black but two may show some tortie...

I truely only know human genetics but imagine this is at least on track for a cat
post #7 of 18
the trouble with the above is that likely neither cat is pure ... pure dominace

here is human eye color

B is brown
b is blue

dad is BB
mom is Bb
child a is BB brown eyes
child b is Bb
child c is BB
child d is bB

all will have brown or hazel eyes , but there kids will have a chance of blue
Bb*Bb= BB bb Bb bB
post #8 of 18
post #9 of 18
Thread Starter 
I think we better stop this discussion, we do not seem to talk about the same thing.

I know the brown/blue eye inheritance, it is the most common example to explain dominance. But it has nothing to do with the gene for red in cats. The gene for red is sex-linked and is not recessive to black. The red gene acts by eliminating eumelanistic pigment (black etc) from the hair fibers, so if anything, red is in a way dominant to black.

Two black cats can never have a red kitten.

The symbol for red is O. A red female is OO, a tortie is Oo (o = not red). A red male is OY. A non-red male from a tortie mother inherits o, whick mean no red gene.

The daughter of a red male (OY) must inherit O because that gene is located on the female chromosome.

Which brings me back to my original question - the baby girl with a red father does not show red (she is not a tortie fenotype). My question is: Must she not be a tortie genotype?
post #10 of 18
this I think shows us were both a bit off..http://www.thecatsite.com/forums/showthread.php?t=27183

It would appear no, unless her white gene has turned off the red... I have a cat that red gene is now on and she is turning from white with orange patches to red with tawny(blondish brown) marble..
post #11 of 18
my problem is that color is not one gene but likely 20 or more ...
post #12 of 18
Thread Starter 
You said further up here in one of your posts that you know human genetics only, not cat color genetics, so there is no point in discussing this more. But thank you for you interest and effort.
post #13 of 18
I am trying to keep it on top so some "expert will come...
post #14 of 18
Here is a great site on feline genetics: http://www.netpets.com/cats/referenc...tgenetics.html
post #15 of 18
Anne is correct, barring a genetic anomaly (either in the child or the parents), or a mutation causing the failure of the red gene, the daughter of a red cat and a black cat MUST be a tortiseshell. Is the female an all over black silver tabby, or is she a black silver tabby w/ white? Because if she has white, the white may have 'written over' most of the red.
post #16 of 18
Thread Starter 
There may be some white, but very little, I am not quite sure (have not seen her for a while). Here she is together with my black smoke tortie (she has red on her back)

two kittens
post #17 of 18
First off, Anne G. The answer to your question would be YES. Every female kitten out of a red male will be red *factored* (expressing red). If the dam isn't red factored too, all the females will be torties.

If the dam is red factored as well (tortie, red tabby or red point), there can be female kittens that are red tabbies and red points, as well as torties. Red is carried on the X chromosome. Being that males are XY, they can only pass their X gene to their female offspring, and since red is carried on X, red males pass red to their female kittens.

As an aside, white (non albino) in cats is a Dominant gene as well. One must have a white parent in order to get white kittens. Bi color in cats is a dominant gene. So is silver (which smoke is the solid form of).

Solid red (tabby) female cats aren't the product of a recessive gene, they simply inherited the dominant red gene from both parents, making them homozygous red, which is a little unusual, but not rare by a long shot, especially if one is working with red. EVERY kitten out of a homozygous red female will be red factored.

Red in cats is different from red in dogs, humans, and everything else, in that it is sex linked. Red Abyssinians aren't actually red, they are cinnamon, which is why you never see tortie abbys.

Hope this helps, Cathy
post #18 of 18
Thread Starter 
Yes, thank you - crystal clear and exactly what I wanted to have confirmed!
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