There have been a couple of Threads lately alluding to a theory that male genes are dominate. It has been my understanding that sex has very little to do with dominance in genes. My understanding from biology is that some genes are dominate, no matter the sex, but both male & female could have recessive genes that when mated result in a visible dominate feature. It isn’t predictable and it is very complicated, therefore breeding fish for certain features/color could take many generations to arrive with even a positive percent of consistency and there would be a lot of fish to be culled out and not allowed to breed.
Dominate/Recessive Genes
- Thread starter Thyra
- Start date
Hello; From memory, I think there are characteristics that are known as sex linked. In humans for example a male carries an XY gene combination and a female carries an XX. Mathematically the ratio during the formation of eggs and sperm is 50/50. The female can only provide an X gene in her egg, while the male may provide either an X (Which makes the fertilized egg an XX female.) or a Y (Which makes the fertilized egg an XY male.)
Characteristics associated with the Y gene when it is present are expressed in the offspring that make them male. I think ( but do not recall clearly this minute.) that when the Y gene is not present and only X genes are present, that these male characteristics are not expressed and the characteristics we consider female are expressed. I believe these are referred to as sex linked. I do not recall, this minute, if this is actually in any way considered to be a form of dominance. It may be in the sense that only when present are the traits associated with Y gene expressed.
I hope that I have not botched this attempt at an explanation, it has been a while since I thought about this stuff. In science, understanding and knowledge are moving targets. New facts are discovered from time to time that change the face of our knowledge and understanding. I have had to discard and replace many bits of understanding in the face of new knowledge, so my understanding and explanation may be as dated as I am. Our understanding may change, but the truth was and will always remain the same.
Characteristics associated with the Y gene when it is present are expressed in the offspring that make them male. I think ( but do not recall clearly this minute.) that when the Y gene is not present and only X genes are present, that these male characteristics are not expressed and the characteristics we consider female are expressed. I believe these are referred to as sex linked. I do not recall, this minute, if this is actually in any way considered to be a form of dominance. It may be in the sense that only when present are the traits associated with Y gene expressed.
I hope that I have not botched this attempt at an explanation, it has been a while since I thought about this stuff. In science, understanding and knowledge are moving targets. New facts are discovered from time to time that change the face of our knowledge and understanding. I have had to discard and replace many bits of understanding in the face of new knowledge, so my understanding and explanation may be as dated as I am. Our understanding may change, but the truth was and will always remain the same.
This was from 8th grade science for me, thnx so much for triggering my memory, Y is the dominent gene in the male and X1 is the dominent in the female i belive. Very complicated process but you can actually make a map out of which fry would be getting what (theoretically) but you'd have to know which is dominent in the male and female (dark colors i guess?) So in theory, you have a Dark Blue tailed female and a Dark yellow bodied Male you get a Dark blue tailed dark yellow bodied fish? I am going to ask my biology teacher monday about all this and see if i can get some notes for a Sticky here 
The main problem is, you can't look at a creature and tell what chromosomes they carry. Case in point: We bred horses and I happen to know that the bay color is considered "dominate" , but I had a true bay mare that was bred three different times - once by a bay, (who had a bay mother) again by an Appaloosa bay with white blanket (who had a sorrel mother), and the last time by a leopard Appaloosa (also a sorrel mother). I owned the stud books and found no history of black, -- but all four foals (she had twins the last time) were black. (And remember; black is not dominate in horses)
It takes years to breed for any particular characteristic and in the process you would have to cultivate out a lot of fish and they can breed before you can even tell their characteristics.
It takes years to breed for any particular characteristic and in the process you would have to cultivate out a lot of fish and they can breed before you can even tell their characteristics.
He "discards" a lot of fish in his breeding program to be "pretty sure" to get what he is after and he also says "there are more questions than answers" and he has been at it for years. Interesting article, but I am not interested in breeding fish. IMO it would be far easier to breed for a certain characteristic in Bettas because at least you would know who the sire and dam were. Breeding stock is expensive and inbreeding is a problem and how would you ever know what you were really buying?
Breeding a specific type of guppy seems near impossible because you don't really know what you're starting with, and it would be hard to control who mated with who unless you kept them separate from birth, so I don't have much to contribute other than that it'll be hard. You'd have to breed a few generations on your own just to make sure, and even then you'd be guessing at the genotype by just looking at the phenotype of the parents and the offspring and doing your best with punet squares. You'd also need a list of guppy genes, and if there were only two, and if they were just dominant and recessive or if they were codominant. Human eyes are codominant and thats why we get so many colors, so I'd be willing to bet guppys are as well.
Also, there are such things as sex linked genes that determine things other than gender. Off the top of my head the only one I know is colorblindness which is typically linked to the human Y chromosome, meaning that a woman (XX) with colorblindness is EXTREMELY rare.
Also, there are such things as sex linked genes that determine things other than gender. Off the top of my head the only one I know is colorblindness which is typically linked to the human Y chromosome, meaning that a woman (XX) with colorblindness is EXTREMELY rare.
