Sunday, February 24, 2008

Polled, Scurred and Horned

There are 3 different sets of genes that determine whether an animal will be polled, scurred or horned. Two of them can cause horns, and the other causes scurs. One of the horn genes, and the scur gene are both sex-linked, meaning that the genes are linked with the genes that determine the sex of an animal, and they express themselves differently in females than they do in males.

The first gene I will discuss is commonly found in Bos taurus cattle, that is the European and British breeds. This is the Polled gene, P and p. P is polled and p is horned. This gene is NOT sex-linked, and expresses itself in the same way in both male and female animals.

P is dominant, which means that as long as it is present the animal will be polled. PP and Pp animals are both polled in appearance, however Pp animals may pass on either P or p to their offspring. pp animals, are horned in appearance, and will always pass on the p gene to their offspring.

PP = Homozygous - Animal is Polled

Pp = Heterozygous - Animal is Polled

pp = Homozygous - Animal is Horned

A homozygous horned animal, in this animal the horns are present. Note the shape of the poll.

Another Homozygous horned animal, this animal has been dehorned, but again notice the shape of the poll.

This animal is heterozygous polled. She carries the horn gene, but since polled is dominant the animal is polled in appearance. Note the shape of the poll.

And finally, a Homozygous polled animal. Again note the shape of the poll.

As a side note, this gene is one that is known to mutate fairly frequently, which may result in the occaisonal polled animal being born to a horned animal.

The other horn (African horn gene) gene is known in Bos indicus animals, or breeds of Zebu type animals. Brahman animals may carry this gene. This gene IS sex-linked, and expresses iself differently in females than it does in males. It is written as Af and af. In females, Af is recessive, and requires that there be two copies of Af for the animal to be horned. However in males the gene is dominant, and only one copy of the gene is necessary for the trait to express.

In males
AfAf = Homozygous - The animal is Horned

Afaf = Heterozygous - The animal is Horned

afaf = Homozygous - The animal is Polled

In females
AfAf = Homozygous - The animal is Horned

Afaf = Heterozygous - The animal is Polled

afaf = Homozygous - The animal is Polled

A horned female will always give birth to a horned male, however, her female calves may or may not be horned, depending on what gene was passed on from the sire.

The final option for horn like growths is the scurred gene. Scurs are a hornlike growth that are loosely attached to the head. This gene, is thought to work the same way as the Af gene. With the belief that for a male that is heterozygous for the Sc gene to express scurs, he needs to also carry a copy of the p gene. Sc is recessive to the p gene, where a horned animal may be scurred, but they will not be expressed.

So in males
ScSc = Homozygous - Animal is Scurred

Scsc = Heterozygous - Animal is Scurred, although it is believed that HE must also carry a copy of p

scsc = Homozygous - Animal is Polled

In females
ScSc = Homozygous - Animal is SCURRED

Scsc = Heterozygous - Animal is Polled

scsc = Homozygous - Animal is Polled

Again, a Homozygous female should always have a scurred male calf, and her female calves may or may not be scurred, depending on the sire.

In the case of these three genes an animal may possibly carry or even be homozygous for the horn gene, the African horn gene and the scur gene.

Saturday, February 16, 2008

Blazing Along

We come to the Blaze gene. The Blaze gene, Bl, is incompletely dominant, and is common in the Simmental breed.

BlBl animals generally have a large blaze to a white face. Unlike the Sh pattern, they won't have the other associated white areas. BlBl animals with the ss trait for recessive spotting can look a lot like Sh animals.

Blbl animals have less white, usually a blaze, or even as small as a star or a snip.

Here are 2 Blbl animals. As you can see, the black has a full blaze, and the red only has a star and a snip.

Another thing to remember, is that the ss (recessive spots) gene can give very similar results to the Blbl or BlBl.

Here is a calf that very much looks like BlBl or Blbl. However, as both her parents were solid colored, one can presume that they were both Ss blbl in genetic makeup. They both passed on the s gene, to make her ss blbll

Another calf, his parents were ss blbl and Ss blbl. He ended up ss blbl.

This heifer calf is out of 2 Ss blbl parents. Again both parents passed on the s gene, to make the calf ss blbl. This time the calf has only a small amount of white on the head

Brockling, A Mottling of the Facts

The brockling gene Bc is what causes the brockle or mottled faces and legs we often see when we cross Herefords with Angus. There are many breeds that carry this gene, although most spotted breeds, such as Hereford for the most part do not carry it. Normande cattle are one of a few spotted breeds where Bc is common. Bc is dominant, and all it takes is one copy for the trait to be expressed. The amount of brockling is not increased when there are 2 genes present rather than just 1. The Bc affects all white patterns by putting darker colored areas within the white areas, usually on the legs and face. ss animals that carry this gene will often be spotted as normal, but where white is present on their legs they will be mottled.

BcBc and Bcbc animals will express broken patches of color within white spots. They may tie into the colored areas on the animal, or they may be completely separate. If one copy of Bc is present you will see brockling.

This animals is BcBc, she exhibits more color than white, but that is not always the case.

These 3 are all Bcbc animals. The goggles on the last one are more likely due to the Bc gene than any other.

This animal is also Bcbc, but she exhibits the mottling on her legs also

bcbc animals however will not express the mottling. There are other genes which are thought to cause the goggle eyes in the Hereford and Simmental breeds, so it is possible for a bcbc animal to express similar marking and still be Bc free. There is also thought to be a separate gene that causes the freckle effect sometimes seen within the Hereford breed.

These 3 exhibit the goggle eyes, and are more than likely not due to the Bc gene. As you can see, other than their eyes, they have no other brockling type markings.

Color Sided

Color sided is a common coloration in the Longhorn breed. White Park cattle also exhibit this coloration. Color sided is represented by Cs. Cs is also a incompletely dominant trait. The Homozygous animals will exhibit more than their Heterozygous mates.

CsCs animals are will exhibit a white body, with dark points. The ears, muzzle and lower legs or around the hooves.

Cscs animals however show a varying pattern. Often they will have a white dorsal stripe and white belly with color extending from the head, along the neck and often tapering off as it moves back to the hips. These animals may resemble SpSp animals. The color will often roan or turn splotchy around the edges of the pattern. Animals that carry the Rr and Cscs genes, often will result in an pattern that is very similar to the CsCs individuals.

The cow here exhibits the Cscs pattern, however as you can see she did not pass the Cs on to her calf which exhibits cscs.

and, here is her next calf which she passed the gene onto it is Cscs

cscs animals are again solid colored.

Dilution, An Enlightening Experience

Dilution is the lightening effect we see within the Charolais, Simmental (and some other breeds). There are 2 different genes covering these lightening effects. They are Dc and Db. Dc is mainly seen in the Charolais breed, and in fact Charolais cattle are generally Homozygous for this gene.Db is commonly seen in the Simmental, Highland and Gelbveih.

DcDc animals tend to be white in color. The base color is still there, but it is removed by the Dc gene. This gene works similarly to the roan gene.

Dcdc animals tend to vary in color, from very light to quite dark. But, you can usually see the color to them. Black based Dcdc animals will be gray and red based Dcdc animals will be tan in color.

This animal is ee, ss, Rr and Dcdc. She is Red base, recessive spots, roan and diluted.

This animal is Ee, ShS and Dcdc. Black base, Hereford marked and diluted. Notice she is a lot lighter than the 1st cow, but still dark enough that you can see the white face.

The rear calf is also a Dcdc calf, where as the leading 3 are dcdc, that is not diluted.

DbDb animals on the other hand tend to be light in color, but not white. They will be light tan and silver gray.

Dbdb animals will be darker in color than there homozygous counterparts. Dark gray for the black based animals, and light to golden red for the red based animals.

Here is a good example of a Dbdb animal. Notice she has a more goldeny or orangey tint to her coat. Bred black she may throw grey and bred red she may throw a light red.

dcdc and dbdb animals of course are not carriers of the dilution genes, and will be normally colored, black or red.

Roan, a Mixture......

Roan is a gene that is co-dominant, which means that traits are equally expressed. That is that you will see both coloured and white hairs mixed.

It is on a different locus than the spots gene, and can result in totally white, roan coloured or solid coloured animals. It is represented by R or r.R is roan, r is solid.

RR animals are Homozygous for the roan gene. These animals will be white with the exclusion of some coloured hair inside their or around the ears. These animals can only pass on the roan gene, every single calf they have will either be roan, or white, depending on what genes the animal they are bred with/to pass on.

Rr animals are Heterozygous for the roan gene. These animals will be roan. The amount of roaning on the animal can vary a lot. Some will only have a bit of roaning on the tail, face, hocks or brisket. Some will be mostly white with a bit of colour thrown in hear and there. You can have Blue Roans, Red Roans, Tan Roan, Grey Roan and so on. It all depends on the Base colour of the animal. You can have spotted roans, or white faced roans if the animal also carries one of the spotted genes.

The above 3 animals are all Rr. 1/2 of the calves they produce should be roan when bred to solid coloured animals. Notice the difference in the amount of roaning.

This animal is Ee, ShS and Rr. So she is black base colour (red carrier), Hereford marked and Roan in color.
This guy is ee, ss and Rr. So Red in colour, spotted (recessive gene) and roan.

rr is homozygous for solid colour. These animals will be solid coloured, and cannot pass the roan gene on.

Friday, February 15, 2008

Spots or Not

There are many genes that produce spots and patterns. The one I will cover here is located on the S locus. The S locus is where the Hereford, Pinzgaur and Holstien/Shorthorn/Simmental spots come from, and also solid colored animals.

On the S locus, we have S, Sh, Sp, and s. S is solid, Sh is Hereford pattern, Sp is Pinzgaur pattern and s is the recessive spotting gene. These genes dominancy order is Sh = Sp > S > s. And these genes work in addition to the E locus.

Sh is an incompletely dominant gene. What this means is that if it is present it will always be expressed, but it will usually result in more white when an animal is ShSh than if an animal is ShS, ShSp or Shs. A ShSh animal will usually express a white face, white on the legs, belly and often on the nape of the neck (featherneck). Any of the other combos will usually express white on the face, possibly some white on the belly or legs, and usually a small to no featherneck.

Both of these animals exhibit the ShSh pattern.They are both purebred Hereford. Notice however the difference in the amount of white on them.

This animal is also ShSh, Every calf she has produced has either been a white faced or hereford marked animal.

All 3 of the above animals are ShS. They have 1 gene for hereford markings and the other is for solid colored. The amount of white on them varies, but is generally less than the amount on the ShSh animals.

Sp works very similarly to Sh, in addition it is equally dominant to the Sh gene. A SpSp animal will have white along the back, down the hind end and tail and up the belly. The head, sides and legs of the animal will be colored. SpS or Sps animals will be marked similarly, although usually less white will be expressed. Often only the tail and possibly the belly will be colored. SpSh animals will exhibit the white face, often with a stripe down the back and tail, possibly the tail will be white and there may or may not be white on the belly and feet.

I have no pictures of any Sp animals, so if anyone has some, and the background of the animal I would appreciate it.

S is recessive to Sh and Sp but dominant to s. SS animals will be solid colored. They will not have white on them due to any of the above genes. Although there are other genes that can put white onto a SS animal.Ss animals are also solid colored. They again will not have any Sh or Sp characteristics. You have seen the pictures of ShS animals above, here are some of both SS and Ss.

The 2 above animals are SS. They are homozygous for the solid color, and can only pass on the S gene.

Both of these 2 are Ss animals. You cannot tell by looking at them, but they are both out 1 ss parent, and one S parent.

And finally we come down to the s gene. The s is responsible for the recessive spotting gene. Like the red color gene s can hide, you cannot tell by looking at an animal if it is there or not. s is responsible for the spots in the Holstien, Shorthorn, Simmental and many other breeds. A Shs, Sps or Ss animal will only exhibit the characteristics of the dominating gene. The animal may still pass on the s gene, but you will not necessarily see or know this. ss animals are spotted. if an animal is ss it will always be spotted, and can only pass the s gene on. The spots may be large or small. There may be lots of them or almost none of them. The animal can be almost white, or almost solid colored. The Ss animals are pictured above, here are some ss animals.

All of the above animals are ss. As you can see the amount of white that is expressed can be almost none to lots. There are different genes that affect the amount of white expressed.

This animal is in fact Shs. She looks a lot like a hereford marked animal.

It is actually my belief that the s works with Sh, and that it is not completely recessive. We have too many Sh animals that have extra spots on them for me to believe that it is totally recessive to Sh. Of course, it could be a totally different gene that is working here too. All the above spotting/marking genes have other genes that modify them. That is why some animals express more white than other animals do. It is why ShS animals can have extra white, and why ShSh animals can have extra white. Sometimes the only way to know what genes an animal has is to see what is passed on.

Thursday, February 14, 2008

Black or Red or ......

There are 3 basic coat colors. There is Black, there is Red and there is the Wild coloration. Black, is of course, black, Red is red and the Wild coloration is a combination of red and darker colors. Animals may look almost black, brown or mostly red. They generally have darker areas on the face, neck and/or legs. Bulls will usually be darker in color than females.

Keep in mind that unless an animal is albino (has NO pigment) they always have a base coat color that is one of the above. It may be diluted, or disguised, but it is still there, and will be passed on. It may be hard to tell what the base coat color is, but there is always a base color.

Ed is considered black, E+ is considered wild and e is considered red.

Ed is dominant over E+ which is dominant over e.

Any animal carrying E will be black in color. It doesn't matter whether they are EdEd, EdE+ or Ede, they will be black. But when it comes to passing on genes, only EdEd will always pass on Ed. The other two will pass one either E+ or e 1/2 of the time. This is where the surprises come in. That black cow bred to a black bull, that throws a red calf for example.

This animal is Ede. We know this since she has had a red calf in the past.

This animal is EdE+. Again we only know this because she has produced calves with wild type coloring. She has also produced black calves.

To the best of our knowledge, this cow is EdEd. She has only produced black calves in the past, regardless of what she was bred to.

E+ animals will be black if they also have the Ed. However if the animal is E+E+ the animal will be wild colored, that is be reddish, to brown with darker areas on the head and neck. E+e animals will be very similar to E+E+, although they may be somewhat more red. They will still have the darker areas on the head and/or neck.

Here is a cow that exhibits the wild coloration. Notice the darker area on her face. We do not know if she is E+E+ or E+e, although I am inclined to believe she is E+e.

ee animals will ALWAYS be red. They are homozygous for red and cannot be any other color. They can only pass on the e gene. However, you must remember that if e is in the prescence of either Ed or E+ you will not necessarily see it. Again, this is where those surprise red calves come from!!

This animal exhibits the ee. She is red in color, and only red. She can only pass on the e gene.

Now remember, that the other coat color genes work on top of the base color. As stated earlier, the base color may be diluted or hidden. There are genes that produce patterns, spots, dilutions and stripes. Some will make an animal appear white, or tan or grey. There are genes that place spots of color inside of white areas. But there will always be a base color, with the exception of an albino where the pigment is completely removed from an animal, and this includes eye pigmentation.

The Basics of Genetics.

Genetics follow some basic rules.Firstly there is always 2 genes that work to express a trait, each trait has its own locus. A locus is defined as a place on a chromosome where a gene is located. There may be more than 2 different genes that can be located at a given locus.

Some genes are dominant, some are recessive. Dominant means that if that gene is present it will express itself, it only takes 1 copy for a dominant gene to be expressed. Recessive means that in order for a specific trait to be expressed there must be 2 copies of that gene. Some genes are both dominant and recessive. There are genes that are incompletely dominant. What this means, is that if there are 2 copies the trait will be expressed more fully and, when only 1 gene is present the trait will be expressed, but to a lesser degree.

Once you understand that 2 genes are required to express a trait, the next step is to understand Homozygous and Heterozygous. Homozygous means that there are 2 copies of the same gene at a certain locus. Homozygous therefore means that the animal can only pass on one type of gene from that particular locus. Heterozygous, on the other hand, means that there are 2 different genes located on the same locus. Heterozygous means that the animal has a possiblity of passing either one or the other gene on.

The other big thing to understand when talking about genetics is that each parent passes on 1/2 of its genes to each offspring. There are many different combinations of genes working together to make an individual what it is. There for there are many different combinations of genes that can be passed on. It all depends on what genes are in the 1/2 that get passed on.