Philosophies of Breeding

[knabe]

Each parent does indeed contribute 50% of the genetic material to each offspring. This does not differentiate the dominance of individual alleles transferred, or ultimately the phenotypic performance of offspring for certain traits, if that's what you were referring to.

not true, there are indel's, rearrangements, which allele is expressed not due to simple dominance and probably a few others i've missed and don't know about.

 

[SeannyT]

Each parent does indeed contribute 50% of the genetic material to each offspring. This does not differentiate the dominance of individual alleles transferred, or ultimately the phenotypic performance of offspring for certain traits, if that's what you were referring to.

not true, there are indel's, rearrangements, which allele is expressed not due to simple dominance and probably a few others i've missed and don't know about.

It is true but maybe missing the point of the discussion. The indels and rearrangements refer to a mutation on an animal that already has its genome established (consisting of 50% genetic material from each parent). I mentioned that this 50/50 contribution of genetic material does not relate to the expression of that genetic material, which is where dominance of alleles comes into play.

 

[RyanChandler]

The problem with 'linebreeding on paper' and calculating inbreeding coefficients is that they only lead us to an estimate based on averages.  These averages are, IMO, absolutely worthless as they falsely assume each parent contributed exactly 50% of an individuals genetic makeup, that each grandparent contributing exactly 25% of the genetic makeup, that each great grand parent contributing exactly 12.5%, etc. This is erroneous and not how genetic inheritance works.

It may just be the way you worded it but I'm not sure what you mean by that quote. Each parent does indeed contribute 50% of the genetic material to each offspring. This does not differentiate the dominance of individual alleles transferred, or ultimately the phenotypic performance of offspring for certain traits, if that's what you were referring to.

Each parent contributes 50% of the chromosomes or 50% of the genetic material?

My understanding, as I stated in Librarian's attachment, is that some chromosomes have more DNA base pairs than others and therefore offspring can receive a different 'quantity' of DNA from each parent. 

 

[knabe]

I guess what I was trying to say is that the strand/s expressing on the parent may not be transferred.

This to me is not percent base pairs transferred as is being discussed but may affect what is expressed and may result in different abounds of each parent being expressed.

Sorry for the mixup.

 

[SeannyT]

The problem with 'linebreeding on paper' and calculating inbreeding coefficients is that they only lead us to an estimate based on averages.  These averages are, IMO, absolutely worthless as they falsely assume each parent contributed exactly 50% of an individuals genetic makeup, that each grandparent contributing exactly 25% of the genetic makeup, that each great grand parent contributing exactly 12.5%, etc. This is erroneous and not how genetic inheritance works.

It may just be the way you worded it but I'm not sure what you mean by that quote. Each parent does indeed contribute 50% of the genetic material to each offspring. This does not differentiate the dominance of individual alleles transferred, or ultimately the phenotypic performance of offspring for certain traits, if that's what you were referring to.

Each parent contributes 50% of the chromosomes or 50% of the genetic material?

My understanding, as I stated in Librarian's attachment, is that some chromosomes have more DNA base pairs than others and therefore offspring can receive a different 'quantity' of DNA from each parent.

Apologies for taking this so far off topic. Technically females would have more total base pairs than males since the X chromosome is bigger than the Y, but in terms of genetic material (and number of chromosomes) it is still considered 50/50 as both parents provide DNA related to each gene. However, unless the traits are sex-linked this small difference in "total" base pairs is not going to affect the expression of genes (i.e. performance or phenotype).

 

[RyanChandler]

Apologies for taking this so far off topic. Technically females would have more total base pairs than males since the X chromosome is bigger than the Y, but in terms of genetic material (and number of chromosomes) it is still considered 50/50 as both parents provide DNA related to each gene. However, unless the traits are sex-linked this small difference in "total" base pairs is not going to affect the expression of genes (i.e. performance or phenotype).

Are you saying that despite the Y chromosome being 2.5 times smaller than the X, that the Y chromosome still contains the same amount of DNA? I have always been under the impression that males inherit more DNA from their mother as a result of their asymmetrical chromosomes.

 

[aj]

What about mutations? I have read where almost every individual has a mutation. It may be a difference maker and maybe it isn't. Like lactose intolerance in humans. I have read that this is actually the initial condition.......it happens in humans as they get older to enhance the weaning process. And then there was a mutation that allowed milk to be tolerated a couple thousand years ago. The polled condition the same deal. Humans have the breast cancer gene that can now be tested for. The obese gene that Pharo's cattle have?

 

[SeannyT]

Apologies for taking this so far off topic. Technically females would have more total base pairs than males since the X chromosome is bigger than the Y, but in terms of genetic material (and number of chromosomes) it is still considered 50/50 as both parents provide DNA related to each gene. However, unless the traits are sex-linked this small difference in "total" base pairs is not going to affect the expression of genes (i.e. performance or phenotype).

Are you saying that despite the Y chromosome being 2.5 times smaller than the X, that the Y chromosome still contains the same amount of DNA? I have always been under the impression that males inherit more DNA from their mother as a result of their asymmetrical chromosomes.

Not the same amount of DNA in both chromosomes but with reference to DNA that codes to specific genes they would be considered equal. Not all DNA relates to genes, and in fact most of our DNA is considered "junk" DNA. I'm by no means a geneticist so any more complicated questions would be outside my wheelhouse.

 

[SeannyT]

What about mutations? I have read where almost every individual has a mutation. It may be a difference maker and maybe it isn't. Like lactose intolerance in humans. I have read that this is actually the initial condition.......it happens in humans as they get older to enhance the weaning process. And then there was a mutation that allowed milk to be tolerated a couple thousand years ago. The polled condition the same deal. Humans have the breast cancer gene that can now be tested for. The obese gene that Pharo's cattle have?

Absolutely. Most people (I'm assuming true for cows as well) have several mutations from their inherited parental DNA. If we didn't then we would see very little differences between siblings or offspring from the same parents. Mutations on specific genes can be identified as you mentioned, and can indicate a predisposition to certain disorders or diseases. In some cases these mutations could presumably relate to genes that we would be interested in (e.g. to phenotypic or performance traits).
It's scary to think that on average humans carry 1-2 lethal mutations that, if inherited by both their parents, can cause disorders or death!

 

[knabe]

Absolutely. Most people (I'm assuming true for cows as well) have several mutations from their inherited parental DNA. If we didn't then we would see very little differences between siblings or offspring from the same parents.

not true.  most of the difference between siblings is due to meiosis and crossovers.

 

[aj]

If earths creatures are always mutating a little bit........wouldn't that help keep gens pools out there that might be able to survive changing environments? Did the Bison Antiqious morph into Bison bison?

 

[Dale]

Some of you noted the difference in the size between the X and Y chromosomes.  I don't mean to hijack the thread, but the mother of 3 sons who all graduated at the top of their class referred us to this article.

Heredity Theory Says in Males, Intelligence Comes From Mom

http://www.wsj.com/articles/SB835919711841023500

 

[knabe]

not using the self-defense gene is pretty stupid.

not sure where that gene is located.

europe seems to lack it as well as a good % of america.


cultural suicide is almost mandated in america now.

 

[librarian]

....there is always the possibility that the Y chromosome carries information that can switch "smart" gene on or off-
I looked around trying to get clarity on XBAR's assertions.
I was about to give up, but ran across this.
http://biology.stackexchange.com/questions/36710/are-the-number-of-base-pairs-in-a-given-chromosome-same-between-different-indivi
Are there mutations that would make one (chromosome) longer than the other? If they're not exactly the same, what's the range in length variation?

As pointed out in the other answers, there can be mutations that change the length of the DNA between individuals and even single cells of the same tissue.

There are different processes that can change the genome length. The most common ones are:

micro-indels (insertion and deletions) or sometimes just simply indels: Small changes (1-50nt) [1]. Usually happen during imperfect DNA repair via Non-Homologous End Joining post a double-strand break.
Copy number variation (CNV): bigger variations that generally happen due to deletions and duplications of DNA segments >50bp.
Transposon expansion
Chromosomal translocations
We can ignore microindels and chromosomal translocations for the moment because the former impart only a small change to the genome size and the latter are usually rare and in most cases, are extremely deleterious.

I also read about homology- the same base pair sequence in unrelated individuals (like to like). At this point, I am giving a lot of prepotent inheritance credit to homology and less and less to linebreeding.

 

[Dale]

In the original post there was discussion about composites.  I wonder if we can learn from the dog breeders.  A researcher in Berkeley crossed a border collie with a Newfoundland.  The resulting pups all crouched and glared like the collie and loved water like the Newfoundland; the barking was somewhere in between the quiet border collie and the noisy Newfoundland. 

When these crossbred dogs were mated to each other, unusual behaviors were generated and other traits were also highly variable.  There were dogs that crouched and carried their tails low like the collie, while loving water and barking a lot like the Newfoundland.  Others might be the opposite and never crouch, hold their tail high, and hate water while rarely barking.  Are these the mongrels spoken of by Librarian?

 

[knabe]

i thought you were talking about millenials,couches, safe spaces and perpetual outrage for a second.

 

[aj]

The dog comparison is interesting. I think that that might happen in breeds that way unrelated. I think that the red Angus and Shorthorns are closer related and pretty much bred for the same traits.

 

[knabe]

closer to what.

 

[trevorgreycattleco]

I see the variation play out in my pigs. I've been trying to maintain that nice deep red meat of the heritagebreeds and get the growth of the modern pig. The first crosses always have huge swings in variation in each litter. Once I identified the sow that seemed to be my best overall pig, I began keeping her offspring for the nucleus. I bred that sow to her son and her daughters to their brother. It's amazing how much more consistent the piglets were. They are just behind the crossbreds in grow but all look very similar. I bred my Aussie Shepard to my female dog , Anatolian Shepard, GP, Merema. She had 10 pups and they all looked different. They act different too. I'm a believer in line breeding to fix your type. Too many crosses in a mating produces genetic chaos and it's a crap shoot what you'll get. Unfortunately that other thread got way off track but that was my point on there. You can't claim a 5 way cross calf will do this or that. It's just false.