Never Encourage a teacher -What I know about color genetics Lesson #2A

[Sonoran Silkies]

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As I said earlier, Henk's Basics write-up is excellent and accurate.

 

[Sonoran Silkies]

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I don't see anything that is inaccurate based upon what I've written. I admit that not every detail will apply without exception (such as with sex-linked traits and several of the dilution,extenders, or restrictor colors but then I have even brought those up)

Let me see if I can clarify for you.

I see no conflict between the definitions linked and what I've explained (note I didn't intend to define anything, but rather explain what the outcome of the that definition is in layman's terms).

The groups I've mentioned are those from Van Dort and relate to the discussions of solid colors, dilutions, extension/restriction and patterns in Hutt's Genetics of the Fowl and elsewhere (With the exception of the e-series discussed in Lesson #2). These discussions are based in the phenotypes as expressed by the genes and are not group together to represent closeness on the chromosome (which would be useful in predicting crossing over between gene combinations).

I don't think there's anywhere I said anthing about the blue gene (or silver or mahogany) or whether the base alleles can or can't be mixed. I haven't discussed anything about specific colors up to this point. I did mention (in the first post), in introducing intermediate/heterozygous that some genes do, in fact mix while others are purely dominant/recessive.

Yes, I agree (am aware) pigment color is subtractive and that light color is additive. Its related to the fact that what we register in our brain is actually the combinations of light particles that are reflected off the surface of the pigment (kind of like "seeing" what's no reflected rather than what's absorbed by the pigment. The actions of eumemelenin and phenomelenin are those of pigment just as with the pigments. The point I was trying to making (which seems to have been lost) was that even with just three primary pigments, several combinations can be had to produce others. Most folks can relate to the primary colors of pigments and their interactions rather than the interactions of colored light. For example more would be familar (via experience) with the subtractive affect of mixed primary pigments to produce black rather than primary light adding to producing white - unless I guess if they have theater experience. Or computer graphics experience, or are an engineer or in a related field, or work with photography, or...

What I'm trying to do is to give some basic background information so that those less knowledgable can understand better in asking their questions and understanding the response they get. Its not intended as a biochemical disseration on genetics but enough so that others don;t feel left out of the point others try to make.

My concerns over inaccuracy are explained in my previous post. I am not disputing your grouping together of genes that work in similar manners. What I object to is that you treat the entire group as if it were a single gene with multiple alleles, not as multiple genes, each with their own set of alleles.

 

[mibirder]

(Treading carefully for the moderators. . .)

I guess my sense is that there might be some misunderstanding going on with what I had in mind with these posts. I wanted to present in a series of posts (of which only two have been made) some basic understanding of what goes into color genetics in chickens in a basic, simple, bit by bit approach so that it seems much less overwhelming for everyday hobbyists - especially those who are beginning or don't have a background in hardcore science. I'm not trying to give them everything at once, be so technical/scientific, or discuss all chicken traits beyond color so they to just give up.

I won't disagree that some of what I've posted so far is not complete - but that's by design - a bit by bit approach rather than all at once. I wouldn't necessarily judge incompleteness with accuracy after only a part of a discussion. I intended a series of posts to be looked at in total, building more complete knowledge as it moves along. (For example, when I brought up intermediate or heterozygous traits in the first topic post, it was in the context that some genes can act this way (but not going into an incomplete dominance discussion), it wasn't in the context of all genes acting that way.) Once more understanding or more completeness (of incomplete dominance or another subject) is needed, I would intend to include it at that point.

I do think that someone who already "knows" a subject with any depth might find faults or exceptions to a basic, simple, restrictive description of something that appears to be as complex as genetics, but I had hoped that people will "get" enough that they feel as if they might understand the subject at a greater depth through further study/discussion on their own or with others. They have to start somewhere to gain the confidence that they can "get" it. I had hoped that with a simple approach that might work. I'd rather not spend time/posts debating symantics or the preciseness of one analogy over another, especially in what's intended to be a simple, basic layman's approach to get folks started off. Unfortunately, I haven't seen always seen much of that here or elsewhere.

BTW, I not bailing out at this point. As I said, this also helps me to solidify what I think I know (which is much deeper and wider than I've presented so far.) So regardless of any frustrations (of mine), I'll continue as much and as well as I'm able timewise.

 

[LilQtBear]

I have a question I have been trying to figure out maybe someone can explain to me..


So I have a couple "California white" Which are California Grey roo bred to a White Leghorn - this creats a White bird with some/few black specks..... how and why is this??
But biggest question is, is the white the dominant color? I found a chicken genetics calculator and was trying to figure out what would happen if I bred a blue to this White bird with specs.. but I can decide if im supposed to click the hen as just white, dominant white, or recessive white.... eek?

 

[Illia]

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White itself depends on the breed, obviously in this case the white is dominant white. There's no generic white, - there's dominant or recessive white.

 

[Meara]

When teaching genetics to college undergraduates majoring in biology I assign them an exercise in eye color, humans not chickens The exercise is popular with students and has proven to be an excellent teaching tool. It is also WRONG! It is grossly oversimplified and glosses over any number of details ultimately presenting the inheritance and expression of eye color in humans in a way that simply isn't so. And yet it remains an excellent teaching tool because you simply have to start somewhere and build as you go along. Even though I teach college level genetics I still get lost sometimes following the genetics gurus on The Coop so I think this thread is an excellent idea. I'm sure it will be helpful to many people!

 

[galanie]

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I thought it was perfect. You reviewed the last then moved on. Ignore criticism. I, too, am from a family of teachers yet I'm not a teacher.

 

[becky3086]

Please keep going. I am just learning and have gone over the other pages suggested and have gotten a book but your lessons are reinforcing what I have already learned and helping to explain it. Thanks.

 

[mibirder]

(Trying to move on - the rest of Lesson #2)

Chickens have a double dose or pair of genes from this group (e-series). The pair of genes may both the same (homozygous or pure) or they may be one of one type and the mate (in the pair) of a different type (heterozygous or impure). Here is where it starts to complicate. Even though all standard colors start with this e-series, by adding other genes for color or pattern can change the exact appearance somewhat– that’s why it harder to tell what this pair of genes are in adult chickens. With chicks it’s a little easier because the feathers that contain the added other genes haven’t grown in yet. Some of these other genes may have some affect on the chick down color, but most of the e-series chicks are pretty consistent. These alleles (without the interaction of other genes) control the basic distribution of the two pigments found in chickens.

Let’s start with the easier part – chick down.

E or Extend Black chicks have short down that is black on the backs and an off-white/cream/marble yellow on the belly. Some may have lots of the belly coloring and others may only have a small amount near the “chin”. e can also produce dark leg color – but not always. These chicks remind me of little fuzzy penguins in their black and off white suits.

ER or Birchen chicks have generally brownish forehead and often a white spot on the “chin”. Some breeds the chicks the brown color may even approach a reddish purple. Over all they might look like E chicks but with a brown tint to them.

e+ or Duckwing are one of the easiest chicks to identify. They are light in color with dark brown and lighter stripes down the back. There usually are three darker stripes – one centered and one to each side of the back with a lighter stripe between the sides and center stripe. These are the chipmunk pattern most think of when they see them.

An eb or Brown based chicken almost always has other genes added to it to make a specific color and/or pattern, so the chicks can vary quite a bit. They often will have lots of patterning going on with stripes, splotches, and other markings. They can range from black with yellow bellies to cinnamon with light, unclear stripes.

eWh can be the most varied to identify. These chicks are generally creamy or white, sometimes with faint stripes on the head or backs

Now the complicated ones – the adults. These descriptions are generalizations and may not apply exactly in every single breed and every color variety due to other genes that may go into the make up of a particular chicken or variety. These generalizations hold true if no other genes are influencing the appearance.

E – These are often all black in color, although mottled and barred are two standard color varieties that are also often based on E (if you add other genes). Black, Barred, and mottle can be made on other members of the e-series depending upon other genes present. The sheen or shiny reflection of the black color can vary depending upon other genes that may be present – it might be green (with black enhancer genes), violet (with one of the red genes) or blue (with melanotic genes). Remember that black (or barred and mottled) can be made on other e-series based chickens as well as on E- if you add the correct other genes.

ER – These have slightly different patterns on the males than on the females of a particular color variety. Generally these are mostly all black with red or silver hackles (lower neck) with black center stripe on both sexes. Also red or silver feathers on the shoulders (where top of the folded wing meets the neck) and saddle with the center stripe (the tail end of the back) of the males. One key is that the breast (lower front of the bird) should have fine lacing on the feathers. The lacing may be red, silver (white) or gold. They also generally have dark legs and feet. Just a reminder that additional genes can change or vary these general patterns (as with all the others in the e-series).

e+ The Duckwings are also different in each sex. Males have orange hackles and saddles with black center shafts with black primaries wing (main feathers at the far end), breast, and tail. The secondary wing feathers (closest to the body on the wing) make up the Duckwing hence the name. These secondary feathers show when the male is standing. Without the influence of other genes, the female will have a darker, peppered back with a salmon or reddish breast. Hackle and collars feathers usually have the black center shafts.

eb is the basis for many of the patterned varieties such as laced, penciled, spangled, etc. The adult males are more difficult to identify as such but generally have black shafts on hackle feathers, black tails and duckwings and look similar to the e+ males. The females are similar to the e+ females, except they don’t have the salmon colored breast. They also have the black peppering that the e+ females have. If the pepper is close enough together, it can look like irregular lacing all over the female. Unless certain other genes are present, the legs of eb chickens are most often yellow.

eWh Wheaten adult males at first glance look just like the e+ males. A main difference is that the eWH males lack or have very little black center shafts on their hackle and saddle feathers (which the e+ will have). They also tend to have lighter fluffy on the end of the feather closest to the body when compared to e+. Females look sort of more orangish because their feathers also lack the black center shafts and very little peppering or black dots on feathers.

eWh is a special case depending upon what other genes are present. eWh without black enhancer genes present will be more dominant than eb or e+ - (sort of in third place on a list based upon dominance)but if black enhancer genes are also present, it will be the most recessive of all five.


Because these e alleles will be in a pair, you can have both members of the pair the same, or they can be two different ones. The template of distribution will be that of which one of the pair is more dominant – Generally no mixing or intermediates take place although there sometimes can be some influence of mix pairs depending the whole set of genes in a single bird.

Keep in mind that chicken colors and patterns are not just made from the actions of a single gene. These e alleles just create a general “template” for the rest of the genes to build upon. In general terms, the e series alleles will determine where the black and/or red based pigments will be found. It’s sort of like a paint by number line drawings with some exception rules. The exceptions are that you can’t just put any color anywhere– some of the areas generally will have to be black and other areas have to be red (or a shade of it). The actual or exact appearance of these areas or shades might be modified or changed a bit depending upon other genes that might be present.

The info so far isn’t all there is to color in chickens, its just the starting point. So far we just have a template or basic distribution to start building the color and final pattern for a chicken.

Dave
More coming when time permits. Per someone's request, I'll just keep adding lessons here rather than on a new topic post.

 

[tadkerson]

Just wanted to say I am going to stay out of this thread. If some one has a question feel free to PM me.

Tim