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Unique Feathering Genetics Questions

post #1 of 8
Thread Starter 

Hey! I'm doing a 4-H presentation on unique chicken feather genetics, and have a couple questions about Silkies and Naked Necks.

 

One part of my presentation is on Silkie feathering (the "hookless" feathering, not just the breed), however I haven't had enough experience with silkies to know much about the genetics involved in crossbreeding them.

 

The naked neck genetics I'm unsure of,  involving the bowties and breeding with normal-necked birds. I just put a rough draft of what I would initially think of if breeding naked necks. Completely open to alteration suggestions. :)

 

Here is what I am assuming with genetics involved in each, and what I have observed in the past. Anyone have something to add or change to either? Punnett squares would be helpful as well. :)
•Silkie + Silkie = 100% Silkie
•Silkie + Smooth = 100% Smooth (These birds now carry the Silkie gene.)
•Silkie + Smooth (w/ Silkie Gene) = 50% Silkie, 50% Smooth (w/ Silkie gene)

 

Naked + Naked = 100% Naked Neck (Two Copies of Gene)
Naked + Normal OR Bowtie + Bowtie = 100% Bowtie (One copy of Gene)
Bowtie + Normal = 50% Bowtie, 50% Normal
 
Thanks in advance for any input! :)
Proud 4-H'er for the last 6 years! Current projects are Poultry and Leadership. Past projects are Pocket Pets (hamsters, sugar glider), and Rabbits. Near future projects may include Goats!
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Proud 4-H'er for the last 6 years! Current projects are Poultry and Leadership. Past projects are Pocket Pets (hamsters, sugar glider), and Rabbits. Near future projects may include Goats!
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post #2 of 8

naked neck (Na) is an incompletely dominant gene, incomplete dominance indicated by the bowtie

 

Na/Na = naked neck

Na/na+= bow tie

na+/na+=normal feathering

 

bowtie x bowtie = normal, bowtie, naked neck

 

this is a hybrid (heterozygous) cross so when two incompletely dominant birds are crossed the offspring will be of three different phenotypes


Edited by Wappoke - 4/16/16 at 6:28am
post #3 of 8

It's a common mistake to say the birds pure for Na are totally naked necked. In fact a huge majority of pure Na birds have small bowties.  Clean necks appear to require a separate modifier gene of sorts and are actually rather uncommon.

 

There is also another thing:  pea comb reduces the overall number of feathers on a bird, normally it is not observable.. however on a naked neck the effect becomes obvious. 

 

Example: naked neck crossed with a normal feather pea comb chicks are more naked and often have a small bowtie compared to crosses with single combs- normally huge bowties that are more like bibs, covering up most of the front neck.  The pea combed naked neck chicks also have a different naked pattern, especially around the face.  The difference is obvious.

 

I have not seen anything about rose comb and feathering, however it can make the chicks more naked, although less so than with pea comb.

 

The point of including this is the mention of silkies.  Silkies are either rose comb or walnut (they are said to be walnut however in reality a majority are actually modified rose, lacking the pea comb gene). So working with showgirls(naked neck silkies) it can seem to prove the clean necks are pure Na when it simply could be side effects of having rose/walnut. 

 

This is all a very good reminder that genetics lessons are best started with mutant gene bred with wild type version...  otherwise the results can be skewed by seemingly totally unrelated genes....


Edited by Kev - 4/16/16 at 8:47am
post #4 of 8
Thread Starter 
Ok, I've decided to take the Naked Neck part out to shorten the presentation a bit. I'm still wondering about the Silkie feathering.

•Silkie + Silkie = 100% Silkie
•Silkie + Smooth = 100% Smooth (These birds now carry the Silkie gene.)
•Silkie + Smooth (w/ Silkie Gene) = 50% Silkie, 50% Smooth (w/ Silkie gene)

Is this correct? Or, is it more complicated that that? I'm going to be talking to people who probably don't know much about chickens, so I'd like to keep it as simple as I can.
Proud 4-H'er for the last 6 years! Current projects are Poultry and Leadership. Past projects are Pocket Pets (hamsters, sugar glider), and Rabbits. Near future projects may include Goats!
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Proud 4-H'er for the last 6 years! Current projects are Poultry and Leadership. Past projects are Pocket Pets (hamsters, sugar glider), and Rabbits. Near future projects may include Goats!
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post #5 of 8

Yes that's correct.

 

I think the naked neck still could be fun and educational, as truly 100% dominant genes are rather uncommon or skip that part and use them to explain how a gene can be dominant but not 100% with there being a visual difference between a bird with one dose vs 2 doses- and how that can aid someone in selection.. if someone wants to create a pure breeding flock of NN,  one can get away with selecting the ones with smaller bowties and cull out the large bowties.

 

Also if possible, introduce the idea of genetic labeling such as h for hookless with H being the wild type(smooth) and introduce Punnett squares so they could make simple and fun game of percentages.

post #6 of 8
Thread Starter 

Awesome, that's what I was hoping to hear. Now I don't have to change anything! :P

 

That's actually exactly what I was planning to do! :) They have a whiteboard on the wall behind where I will be presenting, so I will be using Punnett squares for Frizzle genes and Silkies. Here is one I found online that I put in my powerpoint as an example, but I will be using the whiteboard to show different combinations. That's also kind of why I took out the Naked Necks, because it doesn't work as straightforward as a Frizzle or Silkie in a Punnett square. Also, naked necks don't really go along with the theme of unique feathering -  sure the bird looks different, but the individual feathers look the same as any other birds'.

 

Proud 4-H'er for the last 6 years! Current projects are Poultry and Leadership. Past projects are Pocket Pets (hamsters, sugar glider), and Rabbits. Near future projects may include Goats!
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Proud 4-H'er for the last 6 years! Current projects are Poultry and Leadership. Past projects are Pocket Pets (hamsters, sugar glider), and Rabbits. Near future projects may include Goats!
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post #7 of 8

Frizzle has the same 'complication' as Na and is a reminder of how truly dominant genes are rather uncommon.

 

There is a visual difference between Ff and FF, same as Nana and NaNa.

 

The FF are called 'frazzles'- excessively curled and brittle feathers, very prone to breaking and many of them are semi naked from sparse feathering and/or the feathers breaking so easily and early, rendering the frazzles naked for half of the year.  They also unfortunatley have some health problems due to enlarged organs and abnormal metabolism.   For this reason, breeding frizzle to frizzle is very strongly discouraged.

 

No ill effects with NaNa though.

 

I really do commend wanting to teach genetics- it is very fun....    and if the audience is not going to breed poultry it is perfectly fine to use frizzle or naked neck examples and skip all of what I said about the "nuances"(lol) of those genes and present as-is, just be prepared to do some filling in if someone looks it up and questions you later on..   but if someone is going to breed frizzles, it IS a good idea to explain while that is how genetics work, it is not a good idea to carry out in practice.

post #8 of 8
Quote:
Originally Posted by ClickerChick View Post
 

Awesome, that's what I was hoping to hear. Now I don't have to change anything! :P

 

That's actually exactly what I was planning to do! :) They have a whiteboard on the wall behind where I will be presenting, so I will be using Punnett squares for Frizzle genes and Silkies. Here is one I found online that I put in my powerpoint as an example, but I will be using the whiteboard to show different combinations. That's also kind of why I took out the Naked Necks, because it doesn't work as straightforward as a Frizzle or Silkie in a Punnett square. Also, naked necks don't really go along with the theme of unique feathering -  sure the bird looks different, but the individual feathers look the same as any other birds'.

 

 

 

The frizzle gene has a modifier which makes things very complicated.

 

Read below

 

When thinking about modifiers, it must be kept in mind that modifiers can be dominant or heterozygous incompletely dominant or even recessive. Modifying alleles that are homozygous dominant may alter a phenotype differently than if the modifying alleles were heterozygous. The incompletely dominant frizzling phenotype and the action of its recessive modifier is a good example of how modifiers can work to produce differing phenotypes; there are 4 different phenotypes that can be expressed:

 

1.) In the unmodified homozygous frizzled phenotype, every feather is extremely recurved with vanes that are narrow and curled around the rachis; none of the vanes have the normal slightly concaved appearance. The curving of the vanes around the rachis makes the feathers very narrow. This homozygous phenotype imparts a wooly appearance to the bird. The feathers are also brittle and break off easily, over time the fragile state of the feathers produces a bare bird. The wings of the homozygote may contain feathers that are at different stages of growth (Hutt, 1930; Hutt, 1936; Somes, 1990).

 

2.) In the unmodified heterozygous frizzled phenotype, many feathers recurve toward the head of the bird while others curve up and away from the body producing feathers that are perpendicular to the bird’s skin. Long thin feathers in the male’s saddle and neck hackles may take on the appearance of a curled ribbon. On the apical end (the end away from the skin) of each deformed feather, small sections of the vanes are twisted and partially curled around the rachis of each feather. The wing feathers (less so in the secondary’s) and outer tail feathers exhibit some frizzling (parts of the vanes tend to curl). The inner tail feathers exhibit less frizzling. This phenotype is much appreciated by the poultry fancier. It is the phenotype found in frizzle show birds (Hutt, 1930; Hutt, 1936; Somes, 1990).

      

 3.) In some cases, the modified heterozygous frizzled phenotype looks very much like a non-frizzled phenotype. The modifier inhibits the frizzling allele. In this somewhat normal looking phenotype, the body feathers of the birds exhibit very little recurving or upward curving which is associated with an unmodified phenotype. The inner tail feathers usually have normal concave vanes and the feathers in the wing are usually normal in appearance. If a bird is believed to be frizzled and is closely examined, a few ruffled feathers can be found on the bird’s neck and the outer tail feathers will exhibit a small amount of vane curling. The curling is found on the inner vane away from the feather’s tip. These signs indicate the bird is modified heterozygous frizzled (Hutt, 1930; Hutt, 1936; Somes, 1990).

 

4.) The modified homozygous frizzled phenotype has a soft and furry appearance; different than the unmodified homozygous frizzle’s wooly look. Each feather is curled. The curling of the vane around the rachis starts away from the end of the feather. The vane at the end of the feather will be narrower but have a more normal appearance. This phenotype is inhibited by the modifier and produces a bird that is different than the unmodified frizzled phenotype (Hutt, 1930; Hutt, 1936; Somes, 1990).  

 

 

 

Somes, R.G. Jr., 1990a. Mutations and Major Variants of Plumage and Skin in Chickens.

ed. R.D. Crawford, p.178. Amsterdam:Elsevier

 

 JOURNAL OF GENETICS

Volume 22, Number 1 (1930), 109-127, 

The genetics of the fowl
I. The inheritance of frizzled plumage

F. B. Hutt

 

 

JOURNAL OF GENETICS

Volume 32, Number 2 (1936), 277-285, 

Genetics of the fowl
V. The modified frizzle

F. B. Hutt

 

 

 

When dealing with dominant genes, there is always the problem of expressivity. Expressivity is not always the same in every chicken. A good example is found in birds that carry one dominant white gene. If a bird has the correct genotype and carries one dominant white gene, the bird could be completely white, and another bird has a few black feathers in the plumage and another bird be a very light grayish color.  These are different levels of expressivity.  

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