Obviously the ideal situation would be to mate two animals that are not related to each other at all. With a small herd, however, this might not be possible.
In terms of mating related animals, my basic knowledge of genetics would tell me that brother to sister would be less unacceptable that father to daughter (because the ratio of grandsire in the offspring would be the same in the former and more concentrated in the latter). But is even this too dodgy?
Give that the breed had, at one point, got to such a low gene pool, there must have been a lot of such interbreeding the past?
Inbreeding? - What are ther rules and risks?
I suspect my herd is probably the closest bred worldwide. The danger is in doubling up, with an animal that carries a lethal or undesirable gene, and the chances are, that only by inbreeding will you uncover it. I have a number of animals at this moment, apparently perfectly healthy, from both these types of mating. I have always used a young bull on his dam, in order to see whether it brings anything out. If you can breed this close without harm, you have an animal with few undesirable genes; all animals are likely to carry one or two lethals. My herd has been entirely closed for over 30 years. Scientists use families of rats in their experiments that have been inbred for generations. The recent hedgehog plague on a Scottish island was due to one pair, which had multiplied.
My advice would be, if you like an animal well enough, it is worth trying, if you have any doubts about him or her, then don’t.
My advice would be, if you like an animal well enough, it is worth trying, if you have any doubts about him or her, then don’t.
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The Whitfield Herd
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OK, as luck would have it, I happen to work with someone who has a PHD in Genetics, so I asked him about this, and here is the low down.
Facts. The bull and the cows only share the sire, not their respective dams.
There are two types of DNA, those on the X and Y chromosomes and mitochondrial DNA. Mitochondrial DNA (which governs things like respiration) can only be passed from the mother, and as none of them share a mother this is not relevant here.
Males are XY and females XX. Everyone gets one chromosome from its mother and one from its father. So as the bull is XY, the Y must have come from its sire (as its dam, being XX would not have a Y to pass on). The cows on the other hand must have got one of their X chomosomes from the shared Sire (since they didn't get the Y) and the other from X from their dams.
So, as the dams are all different, the bull and the cows have no DNA in common.
Therefore it is perfectly safe to mate them :D
Facts. The bull and the cows only share the sire, not their respective dams.
There are two types of DNA, those on the X and Y chromosomes and mitochondrial DNA. Mitochondrial DNA (which governs things like respiration) can only be passed from the mother, and as none of them share a mother this is not relevant here.
Males are XY and females XX. Everyone gets one chromosome from its mother and one from its father. So as the bull is XY, the Y must have come from its sire (as its dam, being XX would not have a Y to pass on). The cows on the other hand must have got one of their X chomosomes from the shared Sire (since they didn't get the Y) and the other from X from their dams.
So, as the dams are all different, the bull and the cows have no DNA in common.
Therefore it is perfectly safe to mate them :D
I find this reply rather confusing. If the example is referring to half brother and sister they will certainly be less inclined to pick up the same genes, but could do. Even full brother and sister may share no common genes, but may carry almost identical, it is simply a matter of chance. In the case of father daughter mating, the daughter must carry half of her female chromosomes from her sire. Which type of mating gives a greater chance of doubling up on an undesirable gene cannot be predicted with certainty.
Way above my head this, but I thought inbreeding found out the undesirable genes quicker and thus with scrupulous culling of undesirables it was possible to 'fix' the types wanted and end up with fairly uniform desirable animals. Early life vigour needs to be watched. The normally practised outcrossing provides a glorious lottery as to what might appear or be hidden. I now wait to be told that this long held belief is quite untrue ???
Yes, Ryan and Sylvie you are both right, and I have made an error in referring to ‘half her ‘female’ chromosomes from her sire, when what I meant were her ordinary non-sex chromosomes. The sire carries one Y chromosome and one X, the Y being short of genes. The female has two X, all the balance are identical in both sexes, and the progeny will collect an indiscriminate but one complete mix from either parent. The advantage of in-breeding is that the animal is more likely to receive the same desirable gene for any character from both parents, and must pass it on to its calves. The danger is that if the two identical genes thus received are for an undesirable recessive, it will mean the animal will reproduce it in due course in its progeny, assuming it is not a lethal in which case the calf would be dead.
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The Whitfield Herd
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Ryan wrote:I think the fact that offspring get the majority of their genes from chromosomes other than the sex chromosomes of their parents (i.e. the X and Y chromosomes) has been overlooked...even by a PhD in genetics.
Ah, no.
My geneticist friend looked a bit bemused :p when I mentioned this to him, and said that only one cell comes from the father and one from the mother. A complete set of chromosomes is in each cell, which after fusion multiply and condense. Wikipedia to the rescue :D
http://en.wikipedia.org/wiki/Gamete
"A gamete is a specialized germ cell that fuses with another gamete during fertilization (conception) in organisms that reproduce sexually. In species which produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual which produces the larger type of gamete -- called an ovum (or egg) — and a male produces the smaller type — called a spermatozoon (or sperm cell) in animals, and a pollen grain in higher plants.
The creation of gametes is called gametogenesis, and during it gametocytes divide by meiosis into gametes. Organs that produce gametes are called gonads in animals, and archegonia or antheridia in plants. The term gamete comes from the ancient Greek γαμετης (spouse).
Gametes are haploid cells; that is, they contain one complete set of chromosomes (the actual number varies from species to species). When two gametes fuse (in animals typically involving a sperm and an egg), they form a zygote — a cell that has two complete sets of chromosomes and therefore is diploid. The zygote receives one set of chromosomes from each of the two gametes through the fusion of the two gamete nuclei. After multiple cell divisions and cellular differentiation, a zygote develops, first into an embryo, and ultimately into a mature individual capable of producing gametes. Gametes from a mature diploid individual are produced in the gonadal tissue through meiosis —a process of cellular division that reduces the number of sets of chromosomes from two to one (i.e., produces haploid gametes).
The diploid somatic cells of an individual contains one copy of the chromosome set from the sperm and one copy of the chromosome set from the egg; that is, the cells of the offspring have genes expressing characteristics of both the father and the mother. A gamete's chromosomes are not exact duplicates of either of the sets of chromosomes carried in the somatic cells of the individual that produced the gametes. They can be hybrids produced through crossover (a form of genetic recombination) of chromosomes, which takes place in meiosis. This hybridization has a random element, and the chromosomes tend to be a little different in every gamete that an individual produces. This recombination and the fact that the two chromosome sets ultimately come from either a grandmother or a grandfather on each parental side account for the genetic dissimilarity of siblings."
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The Whitfield Herd
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I still think people are not necessarily getting the right end of the stick here. If, for example, there are 23 pairs of chromosomes, only one of those pairs has the XY combination (in the male) which, after splitting into X and Y during gametogenesis, will combine with the other (female, X) gamete during conception to give either the XX or XY combination and hence determine the sex of the offspring. The other chromosomes also carry genetic material which determine many factors, but will not determine the sex of the offspring.
Ryan
Carmarthenshire
Carmarthenshire
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Kirk- Cascade Herd US
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Two important terms are Homozygous and Heterozygous. Homozygous means the pair of genes are the same, heterozygous means they are different. For example, a black animal carrying red, or a polled animal carrying horns is considered heterozygous for those traits. A black animal with two black genes (not carrying red), or a polled animal with two polled genes (not carrying horns) is considered homozygous for those traits.
If an animal is homozygous for many of its traits, then it must pass those genes to any offspring in the genetic shuffle of sexual reproduction. If an animal is heterozygous for many of its traits, then it may pass those traits, or it may pass other hidden traits to any offspring.
Animals with a great deal of homozygosity are considered pre-potent and strongly stamp their offspring with their traits. Animals with much heterozygosity have a hodge-podge of offspring.
There are only two kinds of breeding. Inbreeding and Outbreeding (Outcrossing). By definition, all animals of a breed share some degree of relatedness, some rather distant.
Inbreeding means the pair of animals are more closely related than the average for the breed. Outcrossing means the animals are less closely related than the average for the breed. Linebreeding is a special type of inbreeding where one attempts to concentrate the genetics of a particularly strong ancestor by repeating that ancestor in the pedigree. Some people use the term linebreeding for just plain inbreeding (because it sounds better).
Inbreeding creates homozygosity. If the closely related parent stock have excellent genes, then you tend to double-up on identical excellent genes. If the parent stock have poor genes, then you double up on poor genes. Inbreeding is an important tool that expert breeders use to create a consistent family of animals that are better than the average animal in the national herd. In the hands of the inexperienced, inbreeding can lead to creating a family of animals worse than the average animal in the national herd.
Outcrossing leads to heterozygosity. Continual outcrossing leads to inconsistency and usually results in an average herd because of the continual mixing with the national herd. Many expert breeders occasionally use a carefully planned outcross to correct any flaws in their inbred/linebred herds.
Those not interested in doing inbreeding themselves, can make great gains by using an excellent bull from an inbreeding/linebreeding herd vs. an equally excellent bull with an outcrossed pedigree. The inbred bull (homozygous) will stamp his mark on your calves, where the outcrossed bull will throw a mix of calves, some with his excellent features and some with his hidden genes (perhaps poor features).
When faced with the choice of equally excellent bulls (cows too), always go with one that has many repeating excellent ancestors in the pedigree.
Kirk
If an animal is homozygous for many of its traits, then it must pass those genes to any offspring in the genetic shuffle of sexual reproduction. If an animal is heterozygous for many of its traits, then it may pass those traits, or it may pass other hidden traits to any offspring.
Animals with a great deal of homozygosity are considered pre-potent and strongly stamp their offspring with their traits. Animals with much heterozygosity have a hodge-podge of offspring.
There are only two kinds of breeding. Inbreeding and Outbreeding (Outcrossing). By definition, all animals of a breed share some degree of relatedness, some rather distant.
Inbreeding means the pair of animals are more closely related than the average for the breed. Outcrossing means the animals are less closely related than the average for the breed. Linebreeding is a special type of inbreeding where one attempts to concentrate the genetics of a particularly strong ancestor by repeating that ancestor in the pedigree. Some people use the term linebreeding for just plain inbreeding (because it sounds better).
Inbreeding creates homozygosity. If the closely related parent stock have excellent genes, then you tend to double-up on identical excellent genes. If the parent stock have poor genes, then you double up on poor genes. Inbreeding is an important tool that expert breeders use to create a consistent family of animals that are better than the average animal in the national herd. In the hands of the inexperienced, inbreeding can lead to creating a family of animals worse than the average animal in the national herd.
Outcrossing leads to heterozygosity. Continual outcrossing leads to inconsistency and usually results in an average herd because of the continual mixing with the national herd. Many expert breeders occasionally use a carefully planned outcross to correct any flaws in their inbred/linebred herds.
Those not interested in doing inbreeding themselves, can make great gains by using an excellent bull from an inbreeding/linebreeding herd vs. an equally excellent bull with an outcrossed pedigree. The inbred bull (homozygous) will stamp his mark on your calves, where the outcrossed bull will throw a mix of calves, some with his excellent features and some with his hidden genes (perhaps poor features).
When faced with the choice of equally excellent bulls (cows too), always go with one that has many repeating excellent ancestors in the pedigree.
Kirk
When I was first trying to come to grips with it, I decided the one thing any geneticist was genius at, was to make the subject sound complicated. Broadly the same rules apply to most species.
To try and simplify, not easy in a couple of paragraphs! Imagine a bag with all the genes in it. Sire and dam both have a complete double set in their bag. Each bag contains two collections of genes in strings numbered one to thirty. Each string of genes has its corresponding one bearing the same number, carrying genes for the same qualities, the genes may or may not be identical, from the other parent.. The ‘red’ strings collected from its dam the ‘blue’ from its sire.
At mating the parent pulls strings out indiscriminately, but must donate one complete set of thirty, which could be predominately blue or predominately red. The offspring collects two complete sets, one to thirty, from each parent, each a mix of red and blue, their final collection will not be likely to bear much similarity to either parent, they could be very similar to their siblings, but may not be. Where inbreeding is close over generations there must be increased chance that they will collect some identical genes from both parents.
They have to collect one complete set of strings one to thirty from each parent and ‘the offspring have genes expressing characteristics of both the father and the mother’, mating them together can result in duplicating undesirable or lethal genes.
To try and simplify, not easy in a couple of paragraphs! Imagine a bag with all the genes in it. Sire and dam both have a complete double set in their bag. Each bag contains two collections of genes in strings numbered one to thirty. Each string of genes has its corresponding one bearing the same number, carrying genes for the same qualities, the genes may or may not be identical, from the other parent.. The ‘red’ strings collected from its dam the ‘blue’ from its sire.
At mating the parent pulls strings out indiscriminately, but must donate one complete set of thirty, which could be predominately blue or predominately red. The offspring collects two complete sets, one to thirty, from each parent, each a mix of red and blue, their final collection will not be likely to bear much similarity to either parent, they could be very similar to their siblings, but may not be. Where inbreeding is close over generations there must be increased chance that they will collect some identical genes from both parents.
They have to collect one complete set of strings one to thirty from each parent and ‘the offspring have genes expressing characteristics of both the father and the mother’, mating them together can result in duplicating undesirable or lethal genes.
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Mark Bowles
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When I made my last submission I was trying to translate the excerpt from Wikipedia into plain English, I missed the last two entries when I resurfaced! The explanation of homozygosity and heterozygosity is excellent, but I would take issue on the emphasis on the bull in breeding.
I want to breed a herd of cows and not bulls, and my choice of bull is always governed by his dam and her antecedents, the only information one can obtain directly from the bull are his beef qualities, which may be important, but is so little of what I require, and breed for.
I want to breed a herd of cows and not bulls, and my choice of bull is always governed by his dam and her antecedents, the only information one can obtain directly from the bull are his beef qualities, which may be important, but is so little of what I require, and breed for.