Selective breeding

[Katchit]

Hello; i am new to the forum.

I would like to ask you about selective breeding and the chances of producing a Taurus (bull) that displayed favourable traits and phenotypes of 2 selectively-picked cattle; thus to produce a better offspring as a result.

Taurus have 30 chromosome pairs; so what are the potential outcomes of the breeding?

How do favourable phenotypes become dominant? is that just a result of the phenotype being heterozygous dominant?

Am i correct in thinking that it is important to keep as many different phenotype combinations in genes as possible; as this allows for diversity within a species?!? if the potential phenotypic combinations were reduced; would this mean that the species would begin to look more and more alike with continued breeding?

Thank you for your time and help; much appreciated.

 

[James R]

Hello; i am new to the forum.

Welcome.

I would like to ask you about selective breeding and the chances of producing a Taurus (bull) that displayed favourable traits and phenotypes of 2 selectively-picked cattle; thus to produce a better offspring as a result.

It depends on the particular traits you're looking for. Most traits are not controlled by a single gene, but by a combination of many genes interacting with each other and their environment.

In one generation, you might achieve a small move in the desired direction, but chances are you'll need many generations to make a big difference.

Taurus have 30 chromosome pairs; so what are the potential outcomes of the breeding?

Chromosomes from the parent animals will mix randomly in such a way that for each gene the offspring will have a copy of the mother's gene or the father's gene. The resulting genome is unique.

How do favourable phenotypes become dominant? is that just a result of the phenotype being heterozygous dominant?

In nature, favourable phenotypes become dominant via various selection mechanisms that operate, including natural selection, sexual selection and other types of selection.

In the case of selective breeding, certain phenotypes become dominant as a direct result of the selective breeding. This is "artificial selection" as opposed to natural selection.

Am i correct in thinking that it is important to keep as many different phenotype combinations in genes as possible; as this allows for diversity within a species?!? if the potential phenotypic combinations were reduced; would this mean that the species would begin to look more and more alike with continued breeding?

Yes. And any flaws will also become more common in the population as a whole, making it more susceptible to certain environmental changes.

Any breeder will tell you that inbreeding over several generations tends to produce low-quality offspring, because genetic flaws have more chance of being expressed.

 

[Katchit]

Hi James.

Thank you for the welcome.

Thank you also for your very informative reply.

So; for example; if the bull had excellent muscle; which had been produced as a result of 'double muscling' on his breeding site; but the cow that they were inseminating was just a 'normal' looking cow; the offspring would not necassarily display the amount of muscle that is the phenotype of the bull?!?

If this was the first time the bull and the cow had been 'selected'; does that mean that the chance of getting the exact offspring desired from selecting these 2 animals; is very minimal; i.e. it would take many years to get the offspring desired; and would not have a high probability of achieving that within the first breeding of offspring?!?

Thank you again for your help.

 

[cosmictraveler]

Double muscling in cattle due to mutations in the myostatin gene

 

[Spud Emperor]

So I crossed a Limousin with a lincoln Red a got a Hays converter bull.

Sorry, wrong thread, I was searching for the missing pun thread.

Carry on.

 

[James R]

Katchit:

So; for example; if the bull had excellent muscle; which had been produced as a result of 'double muscling' on his breeding site; but the cow that they were inseminating was just a 'normal' looking cow; the offspring would not necassarily display the amount of muscle that is the phenotype of the bull?!?

That's right. It would be more likely than if you bred two "normal" cattle, of course, but not guaranteed.

If this was the first time the bull and the cow had been 'selected'; does that mean that the chance of getting the exact offspring desired from selecting these 2 animals; is very minimal; i.e. it would take many years to get the offspring desired; and would not have a high probability of achieving that within the first breeding of offspring?!?

Yes. That's why farmers tend to have breeding programmes that carry on over many generations.

 

[Hercules Rockefeller]

Chromosomes from the parent animals will mix randomly in such a way that for each gene the offspring will have a copy of the mother's gene or the father's gene. The resulting genome is unique.

Just a quick clarification/correction:

Mammals are diploid organisms, ie. two copies of each chromosome and, hence, two copies (‘alleles’) of each gene – one from the male and one from the female. So the above sentence should read....

Chromosomes from the parent animals will mix randomly in such a way that for each gene the offspring will have a copy of the mother's gene or and the father's gene.

 

[James R]

Hercules:

I'm a little confused. The female parent has two copies of each chromosome in her genome, and so does the male parent. The offspring ends up with only two sets of its own chromosomes, and as I understand it the makeup of those is a mixture of the ones from the female and male parents. Moreover, whole chromosomes or even genes are not copied verbatim due to crossing over.

Admittedly, I don't understand the process in detail. Am I going wrong somewhere?

 

[Hercules Rockefeller]

The female parent has two copies of each chromosome in her genome,

Correct.

and so does the male parent.

Correct.

The offspring ends up with only two sets of its own chromosomes,

Correct.

and as I understand it the makeup of those is a mixture of the ones from the female and male parents.

Ummm, sort of, but I think we can rephrase that a bit better.

For any given chromosome, an individual will have two copies. As an example, humans have 23 pairs of chromosomes, 46 chromosomes in total[sup]*[/sup]. For any given pair of chromosomes, one chromosome will be of paternal origin and the other maternal. Each sperm and ovum carries a random assortment of one chromosome of each of the chromosome pairs of the genome in question.

Moreover, whole chromosomes or even genes are not copied verbatim due to crossing over.

Crossing over between chromosomes of a given pair during sperm/ovum production will redistribute the combination of alleles that are represented on the chromosome that is finally packaged into the mature sperm/ovum, but every sperm/ovum contains a full haploid complement of chromosomes (ie. one version of each chromosome, and all the genes, that comprises that genome).

-----------------------------
[sup]*[/sup] I’m ignoring the sex chromosomes where males have an unmatched pair, X and Y.

 

[Fraggle Rocker]

I’m ignoring the sex chromosomes where males have an unmatched pair, X and Y.

Also, doesn't mitochondrial DNA come only from the female parent? This is why we can identify "Mitocondrial Eve" and "Y-Chromosome Adam." All men are descended from one single male ancestor 60KYA and all humans are descended from one single female ancestor about twice as far back. "Genetic bottlenecks," right?