Genetic explanation why there are more red tomcats than cats?
Hello dear knowledgeable people,
I've read several times that there are genetic reasons why there are more ginger tomcats than kittens. It has something to do with the chromosomes.
Allow me to quote:
The reason why more male cats have red fur is simply genetic, specifically the X chromosome. This is the dominant chromosome responsible for inheriting red fur. Female cats carry two of these chromosomes, while male cats only carry one. If only the mother cat has the red base color and the father has any other coat color, the result is a red tomcat. Red female cats, on the other hand, are only born if both the mother and father are red, which is, of course, much rarer.
I don't understand why only female red cats can be produced when both parents are red. Can someone perhaps explain this to me in more detail? Do the X and Y genes determine whether the offspring will be male or female? Thank you so much!
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Hello,
The information for the red coat color is actually located on the X chromosome. However, it is not inherited dominantly, but recessively. See:
https://www.miamor.de/magazin/rote-katzen#:~:text=Rote%20Katzen%20sind%20meist%20Kater&text=The%20fur color%20red%20will%20auf,both%20parent animals%20red%20gef%C3%A4rbt%20are.
To explain:
Female cats have two X chromosomes. Male cats have a Y chromosome instead of a second X chromosome.
If a tomcat has the information for red fur on his only X chromosome, then he has that fur color.
If one of the cat's two Xs indicates red, then it matters: Red is recessive, meaning that if the other X indicates something different, the other one prevails. Only if this information is present on both Xs will the cat also have red fur.
During the formation of the gametes, the set of chromosomes is halved. This means that each egg cell contains only one of the mother's two X chromosomes, and each sperm cell only contains either the father's X or the father's Y. After the two have fused, the complete set of chromosomes is present again, either with two Xs, meaning female, or with X and Y, meaning male. The red tomcat passes on the information for red to all his daughters, because they are descended from sperm that received the X and not the Y. He has no influence on whether his sons also have red fur, as the Y they inherit from him does not say anything about it. In the daughters of the red tomcat, it is the second X that matters, which comes from the mother's egg cell. The red fur only develops if the second X also carries this information.
Because, as we said, the information for red fur color is recessive. So, the mother could very well have this information on one of her two Xs, but if the other has something different, then she herself doesn't have red fur. One or the other X will end up in her eggs. In this case, she will have just as many red kittens with the red tomcat as kittens of other colors, of both sexes.
However, if the cat doesn't have the red information on either of the two Xs, then even a red tomcat can't produce red offspring. Only the daughters will then carry this information, but it won't be expressed in them, possibly not until a subsequent generation.
A red cat, on the other hand, carries the information for this on both Xs, thus always passing it on. Her sons each have only one X, which comes from her, so they will all be red. Her daughters only if the information is also on the other X, which comes from the father. Therefore, only with a red tomcat can she have red daughters.
And very briefly: red tomcats are much more common; the color is expressed when it is inherited from the mother. In red cats, this information must be inherited randomly from both parents.
That's not entirely true. Red isn't really recessive.
If a cat has the allele for red fur on one X chromosome and the allele for black fur on the other, both phenotypes develop side by side due to X inactivation. Depending on whether one or the other X chromosome is randomly knocked out in a cell, an individually unique pattern of black and red spots (tortoiseshell or tortie) results.
OK thanks!
Hey thanks…. lots of information.. and definitely well explained, I just get confused at the bottom part, I think you need some prior knowledge. If the mother is red-haired and has XX and the father is brown and also has red in his genes… and father XY is red-brown, then a red female will definitely come out, right? Because XX is from the mother and my X is a girl? Y contains the male genetic information? Or am I misunderstanding something? But according to that there would be more females than males who would be red?
Somewhere I have a mental block…
Lg
Slowly again: the body's cells have a set of chromosomes that can be arranged in pairs, where normally the two in the pair are the same. One of these pairs, however, is out of line: here it is only the females who have two of the same. This chromosome, which females have twice, is called X. Males, on the other hand, have a different looking chromosome called Y instead of a second X. When the germ cells are formed, the pairs are separated, and one of the two chromosomes from the pair ends up in the germ cell, which is a coincidence, and therefore only has half as many chromosomes as body cells. Female germ cells, egg cells, always have an X chromosome, one of the two from the body cells. Male germ cells, sperm, also only have one of the two chromosomes from this unequal pair, either the X or the Y. The cell that results from the fusion then has the full set of chromosomes, i.e. twice the set of body cells. She will definitely have one of her mother's two Xs, and, depending on the case, either the X (in which case she will be a female) or the Y of her father, and then a male. In females, one X is one of her mother's two, and the other is the father's only X. Males also have one of their mother's two Xs, but also the father's only Y.
It's not possible for a tomcat to inherit the predisposition for red but not be red himself. The information is on the X chromosome, and he only has one. If this information is there, then he has red fur. If it's not there, then the information for red isn't present anywhere in his genes, and he can't pass this information on. The Y chromosome doesn't generally contain much genetic information; its main function is as a switch: if it's present, development tends towards male, if it's missing, the body develops towards female. It shouldn't contain anything about hair color. A cat is only red if this genetic information is on both of its Xs. It must therefore also be on the one that comes from its father. He must therefore be red himself, see above, since he passed on the only X he has to his daughter. The fathers of red cats must therefore always be red themselves.
The sons of red queens must always be red, regardless of the tomcat: they only have one X, one of their mother's two, but no matter which one, it has to say red, otherwise the queen wouldn't be red. Their daughters, on the other hand, will only be red with a red tomcat. Otherwise, they themselves have a different color, but can pass on the red trait.
Things get complicated when the red color is genetically combined with black, but Darwinist will have to explain that to you…
The alleles for red and black fur are located on the X chromosome . Tomcats have only one X chromosome, which they inherit from their mother. Their coat color therefore depends solely on the mother's coat color. Female cats, on the other hand, have two X chromosomes, the second of which they inherit from their father (sons, however, inherit the Y chromosome from their father). Whether a female cat has red fur or not therefore depends on both the coat color of her mother and her father.
If a male cat inherits the red fur allele from his mother, he will always have red fur. If his mother has black fur, he will also have black fur. Female cats only have red fur if they inherit the red fur allele from both parents, i.e., they are homozygous . Therefore, the father of a red cat must also have red fur, and a black male cat cannot have a red daughter.
If a cat inherits the allele for black fur from its father and the allele for red fur from its mother (or the allele for red fur from its father and the allele for black fur from its mother), the resulting coat color will be tortoiseshell or tortie . This coat color is inherited heterozygous . Strictly speaking, it is not a coat color in itself, but rather a pattern of black, red, and white spots (the white parts are not inherited via the X link and are not of interest to us here). Both the red and the black allele are therefore expressed side by side. This type of inheritance is called codominance . Because two X chromosomes are required for the tortoiseshell pattern to develop, tomcats (with a few exceptions, which are infertile) cannot be tortoiseshell cats, but only either red or black.
Tortoiseshell is based on what is known as X-inactivation. Because females have one "extra" X chromosome compared to males (in mammals), there must be a mechanism that causes the genes on the X chromosome to be expressed at the same level in females as in males. This "excess" must be downregulated in the female sex, which is known as gene dosage compensation . In mammals, this is achieved through X-inactivation . This means that in each cell, one of the two X chromosomes is largely silenced. It is packed so tightly that the cell can no longer read most of the genes on the chromosome. Under a light microscope, the inactivated X chromosome can sometimes be seen as a Barr body under sufficient magnification. The cell can then only read the genes located on the non-silenced X chromosome. Which X chromosome is inactivated is randomly determined in each cell, independently of the others, at a specific stage of development in the womb. Wherever a tortoiseshell cat has red fur, the X chromosome with the allele for black fur has been inactivated. Where the cat has black fur, the X chromosome with the allele for red fur is inactive. Because the selection of the inactive X chromosome occurs randomly, no two tortoiseshell cats will ever look the same. Even two tortoiseshell cats that are identical and therefore genetically identical will look completely different. However, once a cell has decided which X chromosome to silence, it passes this decision on to its daughter cells. A cat therefore retains "its" tortoiseshell pattern for life.
What are the possibilities for inheritance in detail?
The color of a cat's coat is determined by the sex chromosome. The gene for red coat color is located on the X chromosome. Female cats have two X chromosomes (XX), while male cats have one X and one Y chromosome (XY). Because the gene for red coat color is located on the X chromosome, male cats have only one X chromosome, while female cats have two. Therefore, red coat colors are more likely to occur in male cats.
In other words, 1X is more likely than 2X.
Rot ist rezessiv, d.h. es wird von anderen Farben. die dominant sind, unterdrückt. Das rote Gen muss beim Weibchen (XX) somit doppelt vorhanden sein, damit es sichtbar wird, beim Männchen (XY) reicht das einzelne Gen. Darum sind Männchen häufiger rot.
Addition: The color gene is located on the X chromosome, which is why females (XX) have 2 color genes and males (XY) only one.
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