Euskal Oiloa Chicken Forum

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#51 2012-01-25 01:43:42

poplar girl
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From: Athabasca, AB, Canada
Registered: 2011-06-30
Posts: 3159

Re: Topic 2: Genetics Terms and Definitions

Great idea to work through them a few at a time and leave a few days inbetween for discussion, questions etc :thumbs:

For the ones so far all good suggested edits to the definitions in my opinion. The examples and additional information specific to poultry are great too!

For whatever reason I never thought about the fact that in poultry the female carries two different sex chromosomes (ZW) which is the opposite of humans where the female is XX. But what you said makes perfect sense as for sex linked barring, males can be heterozygous or homozygous (so B/B, B/b or b/b) while females are either B/- or b/- since they only have one copy of the Z chromosome.


Raising red cuckoo (marraduna) Euskal Oiloak and self blue (lavender) & black Belgian Bearded d'Uccles.

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2012-01-25 01:43:42

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#52 2012-01-25 01:50:03

poplar girl
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From: Athabasca, AB, Canada
Registered: 2011-06-30
Posts: 3159

Re: Topic 2: Genetics Terms and Definitions

Oh and um...I may have put the summary list of definitions (the first drafts) is proper alphabetical order now as them being out of order was driving me nuts :oops:


Raising red cuckoo (marraduna) Euskal Oiloak and self blue (lavender) & black Belgian Bearded d'Uccles.

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#53 2012-01-25 02:07:45

Maggiesdad
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From: Louisa County, Virginia
Registered: 2011-10-05
Posts: 1980

Re: Topic 2: Genetics Terms and Definitions

ipf, we are blessed to have you 'holding our hands' and working us through this.  It is very much appreciated. :thanks:

Glen

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#54 2012-01-25 02:26:51

ipf
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From: Salt Spring Island, BC, Canada
Registered: 2011-08-29
Posts: 168

Re: Topic 2: Genetics Terms and Definitions

Why, thank you, Glen!
I'm happy to do it. It keeps me on my toes, too; makes me think about what I "think" I know. It's too easy to get complacent as one ages.
And, everyone, please do chime in if what I say doesn't make sense to you. Let's make it our goal that everyone REALLY understands the basic concepts, by the time we're done.

Last edited by ipf (2012-01-25 02:29:12)

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#55 2012-01-25 12:51:32

Susan
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From: Saskatoon, Sask, Canada
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Posts: 2540

Re: Topic 2: Genetics Terms and Definitions

Pg, let's keep this topic going for another week? Lots to take in.  :wise:

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#56 2012-01-25 13:05:20

Susan
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From: Saskatoon, Sask, Canada
Registered: 2011-06-28
Posts: 2540

Re: Topic 2: Genetics Terms and Definitions

I just read your corrections ipf and first of all thank you :) :) what are you are doing for us is invaluable. The changes you made make it much clearer (and more accurate). I'm thinking "sex chromosomes" should be their own heading and "autosomes" their own for clarity. Other than that, I need to wake up more before I can add anything for discussion :)

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#57 2012-01-25 16:30:12

ipf
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From: Salt Spring Island, BC, Canada
Registered: 2011-08-29
Posts: 168

Re: Topic 2: Genetics Terms and Definitions

"Sex chromosomes" will be covered in "sex linked", which is about the only reason people care about them very much. But if you prefer, I can create a new term.

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#58 2012-01-25 19:52:03

Susan
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From: Saskatoon, Sask, Canada
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Re: Topic 2: Genetics Terms and Definitions

:)   Ok, sounds great ipf

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#59 2012-01-26 01:23:59

poplar girl
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From: Athabasca, AB, Canada
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Posts: 3159

Re: Topic 2: Genetics Terms and Definitions

Susan we will most definately keep this topic open for another week or however long it takes to get all we can from it.

I thought I knew these terms pretty well ipf but it seems I have forgot a great deal of what I once knew. And then on top of that the aspects specific to poultry and EOs in particular I am just learning.

This is a great opportunity to fully understand these terms and start applying that knowledge to EOs or other breeds of poultry!


Raising red cuckoo (marraduna) Euskal Oiloak and self blue (lavender) & black Belgian Bearded d'Uccles.

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#60 2012-01-26 03:27:50

skeffling lavender farm
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From: Wiarton, ON, Canada
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Re: Topic 2: Genetics Terms and Definitions

This looks great IPF.  I'm just a bit too tired to take all this in right now.  The morning will be better to concentrate on it!  Will post more then.  =D

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#61 2012-01-26 03:51:16

Island Girl
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From: Qualicum Beach, Vancouver Isla
Registered: 2011-07-06
Posts: 1403

Re: Topic 2: Genetics Terms and Definitions

Oh dear, I feel like I have missed a lot and need to do some cramming. I think I will print out the post with the wonderful definitions and then I can mark them off as I think I have a handle on them. That will make it a little more 'mobile' for me to take along on road trips etc this week. Thank you everyone for all the hard work that has been put into this already!

XOX Monika

Thanks ipf for the modification list, I think that will work very well for me as I do find the list a little overwhelming :P Time to get the printer working =D

Last edited by Island Girl (2012-01-26 03:59:13)

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#62 2012-01-26 17:18:59

Lisa
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From: near Arthur, Ontario, Canada
Registered: 2011-07-05
Posts: 649

Re: Topic 2: Genetics Terms and Definitions

Terrific work everyone! :thanks:

I'll have to play catch up....


When all else fails, go spend time with your chickens. :)

Pens are currently filled with Red Cuckoo (Marraduna) and Red Basque (Gorria) breeders, Spitz, and Seramas.

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#63 2012-01-30 02:30:41

ipf
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From: Salt Spring Island, BC, Canada
Registered: 2011-08-29
Posts: 168

Re: Topic 2: Genetics Terms and Definitions

Sorry guys; I've got the next few definitions "discussion and suggestions" almost ready to go, but have had visitors from Australia, and have to go off-island tomorrow for medical stuff. Will try to get back in the saddle soon, promise. I think we're on a good track, and wil make progress. PLEASE, post questions and comments about thing that seem confusing, or wrong, or anything.

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#64 2012-02-05 23:54:14

ChestnutRidge
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From: Western Virginia
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Posts: 251
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Re: Topic 2: Genetics Terms and Definitions

Allele  - One of the possible mutational states of a gene, distinguished from other alleles by its phenotypic effect.  There may be one, two or multiple alleles of a given gene and they may be dominant or recessive. For example, say there are two alleles for leg colour: Y (yellow) and  and y (white). Any bird that has YY or Yy will show yellow legs because Y will always be expressed (the phenotypic effect) over y (white) All yy will be white legged (homozygous recessive). 

I have some Silver Ameraucanas from an Ameraucana Breeders Club president, and one had yellow skin which causes willow legs with the darkened layer of pigment, and willow is a DQ.  I asked about them (here on this thread), and she explained that she had inadvertently been given a cock with recessive yellow skin.  So, all of the first generation of offspring had the proper white skin but in the second generation, yellow skin began to pop up as the heterozygous first generation combined to create the homozygous recessive yellow legs.  So, I believe yellow skin is recessive, not dominant.  A heterozygous bird will have white legs.  I just looked it up on BYC to double check before I said anything, and I found this post:

Chicks legs can change colour as they mature.

On the most basic level leg colour can be affected by three things.

There is the white skin gene (W+) & its recessive allele (w) which allows carotenoids to make skin yellow. So white skin is dominant to yellow skin. A bird carrying two white skin genes bred to a bird with two not white skin genes (yellow skin) will have all white skinned offspring.

Then there is the sex linked inhibitor of dermal melanin gene (Id) which inhibits pigment from the dermal layer of skin & its recessive allele (id+), which allows pigment to be laid down in the dermal layer of skin. Id & W+ will give white (or pink) legged birds, Id & w will give yellow legged birds. id+ & W+ will give slate legs with white soles, id+ & w will give willow legs with yellow soles.

Then there is the e-allele. The above genes work mostly on the recessive e-alleles. The most dominant of the e-alleles, extended black (E), would also need other genes present to inhibit pigment from the epidermal layer of skin.

So, when you all have been crossing white legged birds to yellow, what have the offspring had?  Perhaps white is incompletely dominant, accounting for those light yellow legs.

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#65 2012-02-06 01:51:57

poplar girl
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From: Athabasca, AB, Canada
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Posts: 3159

Re: Topic 2: Genetics Terms and Definitions

You are correct Chestnutridge, white skin is dominant to yellow. Susan's example given with the definition of an allele was just a made up example that happened to be the opposite of what is actually true for chickens. ipf's revised definition of an allele and example says:

Discussion:
Mutations are the origin of all genetic variation. But the wild-type, or ancestral, allele is not usually thought of as a “mutational state”, but rather as the basic model on which mutations take place.
While I think the idea of an example is excellent, this one is rather confusing, since it presents pretty much the exact opposite of the true case. The gene governing the white/yellow leg colour is called W. W=white, and w=yellow; white is dominant.

I would suggest:
Allele - One of the possible variants of a gene, distinguished from other alleles by its phenotypic effect. There may be one, two or multiple alleles of a given gene. Where there is only one allele present in a population (e.g. breed), that gene is said to be “fixed” in that population. Alleles may be dominant, partially dominant or recessive. Example: there are two alleles for skin (leg) colour - w (yellow) and and W (white). W is dominant over w. A bird that has two yellow alleles (ww) will have yellow legs, while birds with one or two W alleles (Ww or WW) will have white legs.

I am not sure about the light yellow legs representing the hertozygote (W/w). I will be monitoring this year to see if it's possible to tell. Someone also told me if you look at the skin around the eye it will be yellow if the bird carries one allele for yellow skin. From the literature as far as I know yellow skin is completely recessive to white skin.


Raising red cuckoo (marraduna) Euskal Oiloak and self blue (lavender) & black Belgian Bearded d'Uccles.

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#66 2012-02-06 02:23:56

Susan
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From: Saskatoon, Sask, Canada
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Posts: 2540

Re: Topic 2: Genetics Terms and Definitions

Sorry for the confusion! Yup I just made up a hypothetical example!!  :chairhide:

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#67 2012-02-07 01:20:58

ChestnutRidge
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From: Western Virginia
Registered: 2011-07-05
Posts: 251
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Re: Topic 2: Genetics Terms and Definitions

:funny: Not at all!  I was just making sure we were all on the same page.  It was a very good example - perfectly feasible!

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#68 2012-02-11 23:40:34

ipf
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From: Salt Spring Island, BC, Canada
Registered: 2011-08-29
Posts: 168

Re: Topic 2: Genetics Terms and Definitions

Here is batch two of suggested revisions for the definitions. One question - should I go back and change the definition of "allele" to make it clearer that an individual carries exactly two alleles (which may or may not be identical to each other) at a given locus?
..........................
Original version:
Gene - A unit of heredity, a section of DNA found on a chromosome that codes for a particular protein. The interaction of that protein in the cell and the environment influences the development of a character and sometimes controls it completely.

Discussion: Genes contain more information than just proteins; they also code for RNA. However, for our purposes, it makes sense to consider just those that code for proteins, recognizing that these proteins govern many things beside obvious physical traits, such as disease resistance.

I would suggest:
Gene: The specific portion of the chromosome, transmitted during reproduction, that governs the trait in question. It may (or may not) have several alternate forms (see allele). Each individual bird, for each autosomal gene, will have exactly two alleles (versions of the gene), one on each of the given chromosome pair; these alleles may be identical or may be different. The expression of a gene (i.e. the trait itself) may be more or less influenced by the environment; some traits are almost totally governed by genes (e.g. number of toes, or feather colour), while others are moderately to strongly influenced by environment (e.g. growth rate, or egg yolk colour).

Original version:
Genotype - The genetic makeup of the organism that includes genes without visible effect, along with those revealed by the phenotype. Genotype may refer to the organism’s whole genetic make-up or just a single pair of genes.

Discussion – "phenotype" includes more than just visible traits; for example, disease resistance is part of the phenotype.

I would suggest:
Genotype: The genetic makeup of the organism; it includes all the instructions for creating and maintaining that organism, including physical, biochemical and behavioral traits. “Genotype” may refer to the organism’s whole genetic make-up, or (more commonly, but sometimes confusingly) to just one pair, or several pairs, of genes. Example: the [partial] genotype of a Buff Columbian Wyandotte is eb/eb Co/Co.

Original version:
Heterozygote (Heterozygous) - A heterozygote is an organism that has two different forms of the same genes (called alleles) in a particular locus on a pair of homologous (or matching) chromosomes. When gametes are made (for reproduction) the gamete may have either type of allele, so either version may be passed to offspring.

Heterozygous means to be carrying two types of these alleles (versions of a gene).

I would suggest:
Heterozygote (heterozygous) - A heterozygote is an organism that has two different variants (alleles) of the given gene, one at that gene’s locus on each of a pair of homologous (or matching) chromosomes. When gametes (eggs and sperm) are formed, each gamete may have either allele, so either version may be passed to an offspring. “Heterozygous” means to be carrying two gene variants, or alleles. Birds that are heterozygous at the locus for a given trait will not “breed true” for that trait. Example: Blue chickens are all heterozygous at the Bl locus; the genotype of a blue chicken is Bl/bl.

Original version:
Homozygote- A homozygote is an organism that has two copies of the same gene (or allele) in a particular locus on a pair of homologous (or matching) chromosomes. When gametes are made (for reproduction) the gametes all have one type of allele so only one type of gene may be passed to offspring. The allele or gene in question may be a dominant or recessive gene.

Homozygous means to be carrying two copies of one type of allele (a single version of a gene).

And Hutts Genetics of the Fowl (pg551-2)
http://edelras.nl/chickengenetics/theory.html (very basic from definitions from there, Hutts was better but had less molecular emphasis)

I would suggest:
Homozygote (homozygous)- A homozygote is an organism that has two copies of the same gene variant (allele) at that gene’s locus on each of a pair of homologous (or matching) chromosomes. When gametes are formed, all gametes have the same allele, so that all offspring inherit the same allele.
For an organism to “breed true” it is necessary that the individuals be homozygous for the genes in question. In general, all purebred individuals of a breed or variety are homozygous for the genes that define the breed or variety (“Blue” is an exception).

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#69 2012-02-11 23:52:57

poplar girl
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From: Athabasca, AB, Canada
Registered: 2011-06-30
Posts: 3159

Re: Topic 2: Genetics Terms and Definitions

ipf wrote:

One question - should I go back and change the definition of "allele" to make it clearer that an individual carries exactly two alleles (which may or may not be identical to each other) at a given locus?

Here is the question from the quiz that I managed to catch a lot of people on (probably poorly worded, my fault):
1. A basque chicken can have the following number of alleles for a gene:
One - 0                                                                              
Two - 2                                                                                      
Three or more - 0                                                               
All answers are correct depending on the gene - 7

This would be my explanation (ipf feel free to correct me):

An individual basque chicken would have TWO alleles for a gene. For example a white legged chick that is the offspring of a yellow legged rooster will be W/w so have two different alleles. A yellow legged basque chicken is w/w at the locus for skin color.

As a population basque chickens may have one, two, three or more alleles that can be present for a gene at a given locus. An example of three or more would be the e-series alleles. A marraduna basque chicken should be eWh/eWh (Wheaton base). Other color varieties may be an eb/eb (brown) or maybe E/E (extended black) base. So in the basque chicken population there would be three alleles for this gene but a single individual could only carry two at a time.


Raising red cuckoo (marraduna) Euskal Oiloak and self blue (lavender) & black Belgian Bearded d'Uccles.

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#70 2012-02-12 01:45:13

ipf
Member
From: Salt Spring Island, BC, Canada
Registered: 2011-08-29
Posts: 168

Re: Topic 2: Genetics Terms and Definitions

PG - I thought it was a great question, just the way it was. It made one think, and then made one question the response. I remember thinking "does she mean "a single chicken?" and concluded that you did, so the answer is 2.

The quizzes point out to me where the possible confusions lie, too, which helps me decide where to give examples or more detailed explanations.

So. . . are you going to accumulate a single-item "glossary" sticky, for easy access for all? The trouble with threads is that after the first few pages the meat sometimes gets lost.

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#71 2012-02-12 02:15:11

poplar girl
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From: Athabasca, AB, Canada
Registered: 2011-06-30
Posts: 3159

Re: Topic 2: Genetics Terms and Definitions

Yes ipf, I will make a locked definition sticky when we are all done the first go-round of discussion. I will reference this thread so if members have further questions they can read further or post questions here :)

Very happy to hear the quiz helped, I had fun and learned making it and I hope others had fun answering as well!


Raising red cuckoo (marraduna) Euskal Oiloak and self blue (lavender) & black Belgian Bearded d'Uccles.

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#72 2012-02-12 02:51:05

ipf
Member
From: Salt Spring Island, BC, Canada
Registered: 2011-08-29
Posts: 168

Re: Topic 2: Genetics Terms and Definitions

All - PLEASE critcise, question, correct, or otherwise comment on things you don't like or don't understand (or do like, for that matter). I need feedback and suggestions. Yes, I'm getting some, but I'm still nervous. For those of you that did the original definition drafts - I really hope you don't think I'm being too nit-picky in my suggested changes. I think you did an amazingly good job overall.

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#73 2012-02-12 03:11:49

skeffling lavender farm
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From: Wiarton, ON, Canada
Registered: 2011-06-17
Posts: 2720
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Re: Topic 2: Genetics Terms and Definitions

Yep, I read the question as the Euskal Oiloa, the population, as one bird can only have 2 alleles for a given gene.

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#74 2012-02-12 22:31:59

ChestnutRidge
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From: Western Virginia
Registered: 2011-07-05
Posts: 251
Website

Re: Topic 2: Genetics Terms and Definitions

For interest's sake, here is a post from the SOP thread Maggiesdad referred to earlier:
http://www.backyardchickens.com/t/62307 … st_8346188

Originally Posted by AllenWMiller

Before I go into answering EJB's questions regarding inbreeding and what my thoughts are on the matter; I think some basic definitions need to be made so everyone can easily follow this line of thought on breeding. Now my definitions here are simplistic and are more complicated than I am defining each term. But I don't think it is important for the average breeder or hobbyist to understand the in depth technical and clinical language of genetic breeding. I think if we can follow these simplified version of terms the outcome of understanding good breeding techniques will still be valuable. If at a later date everyone wants to go more into depth then we shall.

Line Breeding: It is fair to say that linebreeding is a form of inbreeding. However, it is done more selectively and with an eye to keeping the inbreeding coefficient (see below for chart) at or below 12.5%. Like inbreeding, linebreeding is an attempt by the breeder to secure, fix or maintain desirable traits within the strain or line.

In Breeding: Is the process of mating parent to offspring and offspring back to parent in an endeavor to retain or improve particular traits or to fix desirable traits within a strain or line. The inbreeding coefficient is often high in inbreeding which is where it differs from linebreeding.

Out Breeding: Is the process whereby unrelated parent stock of the same breed are brought together in an attempt to introduce new traits to a line or strain or to introduce new vitality and vigor into a line or strain that is too inbred.

Cross Breeding: Is the process of mating unrelated parents of unrelated breeds in an effort to achieve completely new offspring possessing the best qualities of each parent often with an eye to creating a new breed or better production stock.

Selective Breeding: Is the process of mating parent stock of the same breed, possessing the best desired traits (usually leading to some standard uniformity) and then culling the offspring to eventually yield the strongest and best examples of the original traits.

Compound Breeding: Using two or more breeding techniques outlined above jointly. Example: Selective Linebreeding, Double Linebreeding, Cross Linebreeding, etc.

Inbreeding Coefficient:

Father/daughter, mother/son or brother/sister → 25%

Grandfather/granddaughter or grandmother/grandson → 12.5%

Half-brother/half-sister → 12.5%

Uncle/niece or aunt/nephew → 12.5%

Great-grandfather/great-granddaughter or great-grandmother/great-grandson → 6.25%

Half-uncle/niece or half-aunt/nephew → 6.25%

First cousins → 6.25%

First cousins once removed or half-first cousins → 3.125%

Second cousins or first cousins twice removed → 1.5625%

Second cousins once removed or half-second cousins → 0.78125%

Third cousins or second cousins twice removed → 0.390625%

Third cousins once removed or half-third cousins → 0.195%

Mendelian Inheritance: States that both dominant and recessive qualities of the parent stock are inherited by their offspring pre-dominately through sex chromosomes and sub-dominately through autosomes (or non sex related chromosomes).

Sex-Linked Inheritance: With chickens, the cock carries two chromosomes for sex while the hen carries only one. So any gene located on the cock chromosome will be passed to both his sons and daughters; while any gene on the hen's sex chromosome will only be passed on to her sons. Thus as exampled by feather coloring and marking being carried on the sex chromosome results of breeding as follows:

Barred Plymouth Rock Cock to Rhode Island Hen results in all barred offspring.

Rhode Island Red Cock to Barred Plymouth Rock Hen results in barred sons only and black daughters.

(This was the first understanding of auto sexing chicks.)

Record Keeping: I know this may seem redundant to mention record keeping but with breeding records must be kept and be clear and concise on how the line or strain is being developed.

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#75 2012-02-13 00:36:41

poplar girl
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From: Athabasca, AB, Canada
Registered: 2011-06-30
Posts: 3159

Re: Topic 2: Genetics Terms and Definitions

Great idea to copy them here chestnutridge! I thought the way he described these definition although simple made sense in most cases. Same with the inbreeding coefficient. There is another post about inbreeding further along I also found interesting.

I wasn't sure about the Mendelian inheritance definition, the part about inheritance being per-dominantly through sex Chromosomes...I don't understand that.


Raising red cuckoo (marraduna) Euskal Oiloak and self blue (lavender) & black Belgian Bearded d'Uccles.

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