The Bull or the Cow

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aussie_cowgirl":3me2c84r said:
Jeanne - Simme Valley":3me2c84r said:
jedstivers - it was always said that the bull has the greatest influence on your herd, because he represents 1/2 of your calfcrop for several years.
aussie-cg - this is interesting, but I'm not quite sure I understand - well, I'm sure I DON'T understand.
I thought I was following what you were saying, until you said "this means the calf is more likely to reflect the mother in traits found on the sex chromasomes if it is a male". I was expecting you to say FEMALE. So, can you explain it in even MORE laymen's terms????? :lol:

Haha. Ok. Heres a picture. (Pictures are easy right? :))
homologous_and_hemizygous.gif

A female's sex genes are XX and a males are XY so if the child is a male it has recieved the Y chromosome from Dad and the X from Mum (seeing as males pass on the Y chromosome.) And as you can see from the picture, the Y chromosome is a sorry looking guy who is missing a huge chunk of the genes contained on the X chromosome. So a bull calf gets its X chromosome from Mum and Y from Dad, but because the Y chromosome is missing so much info, the genes on the X chromosome he got from Mum are most likely to be expressed. Does that make more sense? I get carried away sometimes, sorry :oops:

Aussie Cow Girl - Thank you! It's pretty amazing when an old fart like me can still learn something new. This does seem to jive with much of what we see and other posts. Sort of like finding Newton's laws for the first time! Like a lot of things my kids are covering in school, this just wasn't common knowledge when I took biology many years ago. We did cover the X & Y bit but I don't ever remember hearing that the Y was so much more limited in genes than the X. I guess my wife could have told me that! Jim
 
From that explanation it would mean that not all genes are paired. If each parent passes one half of the pair, what happens to the ones that only the female pass?
 
dun":19gkru8p said:
From that explanation it would mean that not all genes are paired. If each parent passes one half of the pair, what happens to the ones that only the female pass?

All chromosomes are paired and everything matches except for the X and Y in a male. I don't understand what you mean by your question though. In a male where he has recieved the X from his mum and the Y from his dad, he only has one set of genes on that pair of chromosomes. So if a gene on the X chromosome is dodgey he's out of luck. Normally if you have a dodgey gene, the corresponding pair on the other chromosome comes into play. If that doesn't cover it try and reword your question and I'll have another crack.

Jeannie- Absolutely correct. :banana:

Short bus riders- My pleasure. :p
 
The X donated from the sire can only come from his dam is what I have been told.
 
If each parent passes one half of the pair, what happens to the ones that only the female pass?

Dun, traits like colour blindness in humans are hosted on the XY chromosomes. It's a recessive trait, so if the mother passes on an X carrying the recessive and the father has the non-colourblind dominant trait his daughters won't be colourblind (but will be carriers). The boys will be colourblind because they have no matching gene to mask the recessive trait.
Scurs in Angus crosses seem to work in a similar way - the female passes on the trait but only the males express it (unless the father also has the recessive on the X he passes on, in which case the daughters).

eb: I don't think it's that simple. Harking back to high school biology now... but during division traits can cross over between the pairs, so some carried on the Y could in theory end up on the split-off X.
 
EAT BEEF":3ex2sk5j said:
The X donated from the sire can only come from his dam is what I have been told.

Yes. But there will be trait variation. His Dam has 2 sets of X chromosomes so dominant overides recessive genes. BUT if the progeny bull receives 1 X chromosome then some of the genes on that chromosome will be his dam's recessive unexpressed alleles. This is how conditions such as haemophilia skips generations. If the grandfather has the condition, the daughter WILL get the gene (Males have one X chromosome and a daughter has an X chromosome from both parents). If it is recessive she will be what's known as a carrier, so she has the gene but doesn't suffer from the condition and her sons have a 1:2 chance of having the condition.
 

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