cross breeding aythya species (1 Viewer)

[Adam M]

this subject crept up on the staffs thread and im still not totally convinced the answer given is right.

the question is, when aythya species cross breed why do the young show more characteristics from the fathers species?

i thought it would be a usual case of dominant/recessive genes and the young would come out looking like both parents 50/50ish, but apparently not.

its even made more confusing that if, for example, a male pochard breeds with a female tufted duck the young look more like a pochard than a tufty, but if a male tufty breed with a female pochard, the young look more like a tufty than a pochard. to me that showed that there isnt a dominant species and therefore the key factor here really is the species of the father.

sex linked genes were the answer given on the staffs thread, but i though sex linked genes would only express themselves depending on the gender of the young rather than the species of the father.

on a slightly unrelated issue, as sex linked genes manifest themselves depending on the gender of the young (the usual example is red eye/ white eye fruit flies) are different plumages between males and females therefore caused by sex linked genes?

adam

 

[njlarsen]

The following contain my speculations, which may or may not match what others have speculated:

There is the word imprinting which has two meanings: the behavioral meaning which most of us know, and the genetic meaning which is less commonly known. In human (and mammal) genetics there are many examples of genes which has been selectively shot down when inherited from parent of one sex but is active from the other parent; examples of diseases related to such genes would include Angelman, Prader-Willi, and Beckwith-Wiedemann. In this case, it would make sense to hypothesize a gene that influences development that is under this type of control. (my speculation is based on the assumption that you have your data correct, which I have not checked).

For your second question, the answer is "not necessarily". Again with a human example: male pattern baldness which results in males being mostly bald at age 30 is caused by a gene on a regular (autosomal) chromosome, but only expressed in males. If you pump a female who has that gene full of testosterone she would probably loose her hair; if you take the testosterone away from a male with the gene he would not loose his hair, so the control is through the presence of sex hormones. Of course, in humans, the presence of testosterone is ultimately dependent on the presence of the Y chromosome.

Niels

 

[Farnboro John]

it occurs to me (wild speculation only here) that the problem may simply be our definition of a suite of Tufty/Pochard characteristics. My understanding of meiosis and sexual reproduction is that the characters assort randomly so what you may be seeing is simply the superficial characters you think of as Tuftiness or Pochardness, with less obvious things, such as exact shape or wing formula that we don't bother with for ID, being the other way. If you see what I mean.

John

 

[Adam M]

it occurs to me (wild speculation only here) that the problem may simply be our definition of a suite of Tufty/Pochard characteristics. My understanding of meiosis and sexual reproduction is that the characters assort randomly so what you may be seeing is simply the superficial characters you think of as Tuftiness or Pochardness, with less obvious things, such as exact shape or wing formula that we don't bother with for ID, being the other way. If you see what I mean.

John

i get what you mean, the feature we use for ID might be that of the father species, but other things we dont use for ID might be that of the mother species.

it still wouldn't really answer why a pochard x tufty and a tufty x pochard would be different from each other though. the only other example i can think of is lions and tigers cross breeding to produce ligers and tigons. the same happens there with the young taking mainly the features of the male parental species.

if anything the ligers and tigons confuses matter more though, as mammal and bird chromosomes are the other way round when it comes to male and female. XX Xy in female and male mammals and Zw ZZ in female and male birds. note the change of the 'recessive' (lower case) chromosome from males to females.

i have now asked a biology lecturer at my university about the aythya ducks, he is going to look into it and see what he comes up with. i will have to mention the ligers and tigons to him as well and see if he can make sense of that too.

adam

 

[mrpjdavis]

If you look up genomic imprinting in Wikipedia you will find an explanation which probably fits the observations. Unfortunately it is pretty technical. In a nutshell it seems that, in humans at least, there are about 1% of genes where the origin of the allele i.e from mother or father determines whether that allele is expressed or not. This is totally contradictory to the normal (Mendelian) expression of alleles and has nothing to do with sex linked genes such as haemophilia or sex limited genes such as male pattern baldness. A good reference is Matt Ridley's book "Genome". Genetics has been been found to be way more complicated than what I was taught at Uni (albeit 40 years ago).

Pete

 

[njlarsen]

If you look up genomic imprinting in Wikipedia you will find an explanation which probably fits the observations. Unfortunately it is pretty technical. In a nutshell it seems that, in humans at least, there are about 1% of genes where the origin of the allele i.e from mother or father determines whether that allele is expressed or not. This is totally contradictory to the normal (Mendelian) expression of alleles and has nothing to do with sex linked genes such as haemophilia or sex limited genes such as male pattern baldness. A good reference is Matt Ridley's book "Genome". Genetics has been been found to be way more complicated than what I was taught at Uni (albeit 40 years ago).

Pete

And that was the same thing I was trying to get to in the first part of my previous post in this thread

Niels

 

[mrpjdavis]

And that was the same thing I was trying to get to in the first part of my previous post in this thread

Niels

I appreciate that - I was just trying to give some references and a bit more information, since nobody seemed to be saying "Ah, I see what you mean"
Pete