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Posted: Sat Sep 29, 2007 8:32 am
by wagra dexters
Hello everyone, ... and Kirk. Please don't groan at me for raising the 'Red' word again. I read the Qualitative Genetics page. Is there a simple answer for simple people?
Our bull is Black: Ed/E+ Red: E+/E+. Can we expect wild red just as frequently as normal red, from the 50% red probabilities from pale skinned red cows?
Is there no dominance, one kind of red over the other, just the throw of the dice? Or am I way off the mark, and missing something glaringly obvious here?
What happens when the dun gene meets the red gene? I presume it's always black, would that be right?
With the colour genotype of this bull being what it is, how is that configuration inherited from the sire and dam? Who has donated what when there are four figures indicated like that?
Margaret
Posted: Sat Sep 29, 2007 7:50 pm
by Kirk- Cascade Herd US
I'm not certain what you mean by "Our bull is Black: Ed/E+ Red: E+/E+."
At the E locus there are three alternatives (alleles), ED, E+, and Ee (or just plain e). An animal has 2 genes at each locus (one from each parent) and those 2 genes are a combination of the 3 alternatives, so there are 6 possible combinations:
ED/ED (a Black animal - homozygous)
ED/E+ (a Black animal that carries wild-type red)
ED/e (a Black animal that carries true red)
E+/E+ (a Wild type red - homozygous)
E+/e (a Wild type red that carries true red)
e/e (a True red - homozygous)
So if your bull is black but carries wild type red, then he is ED/E+ (one black gene and one wild-type red gene). So he received the ED from one parent and the E+ from the other parent, if one of his parents is red, then the other must be black and the red parent must have contributed the E+ while the black parent contributed the ED.
Your pale skinned red cows that have not been color tested can be any of the last 3 combinations on the above list. The e gene only allows production of red pigment while the E+ gene allows production of red and black pigment. The E+ blend of red and black pigment is controlled by other modifying genes which can allow an E+ animal to be a light-skinned solid red, or a dark-skinned red with much black in the coat (especially as they age, and especially on bulls). So E+ can look like e and have no black shading, but e can NOT have black shading.
So if your bull is ED/E+, then 50% of the time he is going to contribute an ED (black) gene and 50% of the time he will contribute an E+ (wild-type red gene). When paired with red cows that are any of the last 3 combinations on the above list, those cows will contribute one or the other of their 2 genes, each 50% of the time. The 50% of the time that your bull contributes his ED gene to these red cows, those calves will have the black gene and will produce solid black pigment (I'll get to dun in a moment), the 50% of the time that he contributes his E+ gene, you will have red calves from your red cows.
When he contributes his red E+ gene, the resulting red calves will be E+/e or E+/E+ depending on the gene that the cow contributes. So you will have no true red (e/e) calves from this bull, however, some of the calves may look true-red (no black pigment) because of other modifying genes.
Now, if both the bull and the cow each have at least one dun gene at the B locus (brown locus) where the choices are either neutral or dun, and they both contribute a dun gene then the resulting calves that would have been black (because of the bull's ED gene) will have their black pigment softened to a shade of dun. Dun animals are actually black animals with uncooked black pigment because the dun gene interferes with the last step of laying down black pigment and makes the black pigment look brown. So only the first three E locus combinations on the above list can be dun, but only if they are b/b (dun/dun) at the B locus (a dun gene from each parent). b= recessive brown (known as dun in Dexters).
If this isn't clear, please feel free to keep asking questions until it is - most people struggle with this.
Kirk
Posted: Sun Sep 30, 2007 6:03 am
by wagra dexters
Kirk, that is what it says under Genotype on the report from Catapult Genetics (GeneSTAR). Both his parents are black, but the dam is by Outlaw.
Thanks for the information. I gave up trying to find where it was posted before.
Posted: Sun Sep 30, 2007 11:33 pm
by Inger
Kirk, I have a question about telling the difference between a 'true' red and a 'wild' red Dexter.
We have a heifer which looks like this;
http://i30.photobucket.com/albums/c315/ ... 2yrold.jpg
We also have two red calves this year which look like this;
http://i30.photobucket.com/albums....003.jpg
http://i30.photobucket.com/albums....001.jpg
The calves' skin is pink. I forget what Summer's skin was like as a calf. I have a picture of her as a calf though.
What things should I look for to tell the two types apart?
Posted: Mon Oct 01, 2007 3:13 am
by Kirk- Cascade Herd US
There are 3 genotypes of red:
E+/E+ (homozygous wildtype red)
E+/e (Wild type red, carries true red)
e/e (homozygous recessive true red)
The e/e true red cannot produce black pigment, and therefore cannot produce a black shaded red calf (it can however produce a dark, dense red). The wild type red can produce a red with black shading (due to the E+) or a red that looks just like a true red with no black shading. The E+ gene provides the Dexter with the ability to produce both red and black pigment and allows other minor shading genes to use the black pigments to produce various black shading "patterns" like bindle, or jersey-like markings (Jerseys are E+ wild-type, by the way and red Angus are usually true-red e).
If a red Dexter has a pinkish nose and lightish-red coat, it could be either a true-red or a wild-type red, but is more likely to be a true-red. If a red Dexter has a red coat that greatly darkens with age, or has a dark nose and eyelids, or has a brindle pattern, then it is must be a wild type E+.
In your photos, it's more likely that the first red cow is an e/e true red due to the lack of black shading, but, it could be a wild-type with shading genes instructing no shading patterns. The calves both appear to have pink noses and light eye liners so could be true red, but I noticed the tip of the one calf's tail was quite dark, and that is a sign of wild-type red gene. I would guess those calves might have an E+ gene (but I'm not certain). As they age if they continue to darken, you can make a good guess that they are wild-type reds, but with pink noses. Red calves with dark/black noses most definitely have an E+ gene.
hmmm..... does this help?
I know the science behind this, but many other long-time breeders probably have more first-hand experience. Anyone disagree with my post?
Posted: Sat Oct 06, 2007 9:55 am
by Colin
Kirk I found your information excellent. I've not got into the genetics of colour yet so this is an invaluable summary. Where can I get further information on the genetics of naturally polled and horned animals. ? I have a bull from a naturally polled farther and a horned mother. He seems to be a combination, no apparent horn buds initially, but then developed some horny stumps, which have since been removed.
Colin
Posted: Sun Oct 07, 2007 5:46 am
by Kirk- Cascade Herd US
Colin wrote:Kirk I found your information excellent. I've not got into the genetics of colour yet so this is an invaluable summary. Where can I get further information on the genetics of naturally polled and horned animals. ? I have a bull from a naturally polled farther and a horned mother. He seems to be a combination, no apparent horn buds initially, but then developed some horny stumps, which have since been removed.
Colin
In cattle, there are likely two primary loci (locations on the DNA chromosomes) that control horns and scurs. At the horned/polled locus, there are two choices, P (dominant polled) and p (recessive non-polled). An animal inherits one of these from each parent:
Here are the 3 possible combinations:
P/P (Homozygous Polled - a polled gene from each parent)
P/p (Heterozygous Polled - one of each gene)
p/p (Horned - two horn genes required to be horned)
A homozygously polled animal always contributes a polled gene and always has polled calves even when bred exclusively to horned animals. A horned animal always contributes a horned gene, but if the other parent contributes a polled gene, then the calf will be polled since polled is dominant. Two heterozygously polled animals can have a mix of both polled and horned calves. One heterozygously polled animal and one horned animal can also have a mix of horned and polled calves. Horned animals cannot "carry" polled genetics because polling is dominant, but polled animals can carry hidden (recessive) horned genes.
Scurs are a type of horn growth that produces small stumpy false horns (sometimes much larger) that are generally loose and not attached to the scull (but may attach in older animals). A polled animal with scur genes may grow these scurs. A horned animal with scur genes cannot exhibit scurs because the horns override the scurs. There are two alternative choices (alleles) at the scur locus: Sc (scurs) and Sn (no scurs). An animal inherits one of these two alternatives (alleles) from each parent. There are 3 possible combinations:
Sn/Sn
Sn/Sc
Sc/Sc
Scur genetics are complex and are influenced by the sex of the animal. The scur gene is dominant in bulls and recessive in cows. So, it takes two Sc genes for a cow to have scurs, but it only takes one Sc gene for a bull to have scurs. Further, the exhibition of scurs also is influenced by the number of polled genes that the polled animal has; one or two. A polled bull with one polled gene and one scur gene will likely have scurs, but a homozygously polled bull (with 2 polled genes) will likely require two scur genes in order to exhibit scurs. A polled cow with one polled gene requires two scur genes to exhibit scurs, but a homozygously polled cow with two scur genes will likely be smooth headed.
Further complicating this are genes that alter the size and growth of scurs, making them larger or smaller.
Hope this helps,
Kirk
Posted: Wed Oct 10, 2007 9:18 am
by Broomcroft
My lead cow produces totally jet black calves; she just had another yesterday. I don't mean that they are just black all over, which they are, I mean they are intensely black. They're by my red bull. There's not a hint of any other colour or shade even in the young coat, winter coat, any coat. All the others have some sort of other colour/tinge at some stage, but not hers (so far).
Is that of any significance? Is this fairly rare, or just on my farm.
Posted: Wed Oct 10, 2007 5:37 pm
by Kirk- Cascade Herd US
Broomcroft wrote:My lead cow produces totally jet black calves; she just had another yesterday. I don't mean that they are just black all over, which they are, I mean they are intensely black. They're by my red bull. There's not a hint of any other colour or shade even in the young coat, winter coat, any coat. All the others have some sort of other colour/tinge at some stage, but not hers (so far).
Is that of any significance? Is this fairly rare, or just on my farm.
While the genes (ED,E+,e) at the E (Extension) locus are the primary controllers of red and black, and the genes (B,b) at the B (Brown) locus can modify black to be brown (making dun), there are likely many other secondary DNA locations (Loci) that have genes that influence the small amount of red pigment that a primarily black animal has. It is likely that your jet black animal has influencer genes that are suppressing most or all of the small amounts of red pigment sometimes found in black animals, leaving your animal jet black. This effect is probably why some have argued that there are a large number of different shades of black. We also find these many shades of black in our Icelandic sheep (you'll note that humans too have these many shades and the genetics work analogously in most/all mammals).
Warning: 95% of this post is fact and the rest is conjecture.
Posted: Wed Oct 10, 2007 8:35 pm
by Colin
Kirk appreciate the additional information on horn genetics. This is very interesting and useful. It sounds like my bull is polled with scurs, given true horns didn't form, just two strange shaped stumps which have since been taken off. These weren't detached from the skull though. The horn ridge across the top of his head is definitely fused to his skull. But I guess this is part of the genetic variation. He's registered as polled but looks anything but. So I wonder if this is still an accurate statement (it doesn't allow for Polled with Scurs !).
On the degree of blackness question, I've noticed a reddish tinge on some of the longer hairs around the stomach and rear legs of two of my blacks. This seemed more pronounced in the summer when what little sun we had seemed to fade them a little. The photo on the DCS home page clearly has a reddish tinge.
Colin
Posted: Thu Oct 11, 2007 6:49 am
by Kirk- Cascade Herd US
Colin wrote:Kirk appreciate the additional information on horn genetics. This is very interesting and useful. It sounds like my bull is polled with scurs, given true horns didn't form, just two strange shaped stumps which have since been taken off. These weren't detached from the skull though. The horn ridge across the top of his head is definitely fused to his skull. But I guess this is part of the genetic variation. He's registered as polled but looks anything but. So I wonder if this is still an accurate statement (it doesn't allow for Polled with Scurs !).
On the degree of blackness question, I've noticed a reddish tinge on some of the longer hairs around the stomach and rear legs of two of my blacks. This seemed more pronounced in the summer when what little sun we had seemed to fade them a little. The photo on the DCS home page clearly has a reddish tinge.
Colin
It sounds like your bull is P/p (heterozygous polled) and probably Sn/Sc (a single scur gene) although he could be Sc/Sc (two scur genes) but that would be more rare. All animals with a polled gene (or two) should be registered as polled regardless of scurs. I'll bet there are a good number of polled animals, with scurs, registered as horned due to the confusion. I'll bet folks "dehorn" the scurs thinking they are just slow growing horns, never knowing that the calf is polled. Imagine when that "horned" calf later has a polled calf - it would make you wonder where that polled gene came from.
Kirk
Posted: Thu Oct 11, 2007 7:41 am
by Broomcroft
I read somewhere that in Australia, that animals with scurs can't be registered as polled, or aren't regarded as polled.
Posted: Thu Oct 11, 2007 8:21 pm
by Colin
I'd be interest to know what the UK DCS policy is on registering polled with scurs.
My bull will father 4 calves in coming months, which in theory should be 50% polled if he's heterozygous for polled, as none of the mothers are polled. Looking forward to find out.
Colin
Posted: Fri Oct 12, 2007 6:57 pm
by Broomcroft
I asked the question a year or two ago, and was told that polled animals with scurs were considered polled (in the UK).
Posted: Sat Oct 13, 2007 3:17 am
by wagra dexters
The DCAI registration form asks for 'H', 'P', or 'S', in the Horn box.
Margaret.
