How do birds become sexlinked

Discussion in 'General breed discussions & FAQ' started by Zahboo, Mar 27, 2009.

  1. Zahboo

    Zahboo Simply Stated

    Feb 3, 2009
    Hope Mills, NC
    I am wanting to learn more about genetics. I'm trying to grasp the lavender thing, with split blacks, and lav, and black without lav and wow it's tought... If you can explain that, try


    BUT I want to know how a chick becomes sex linked, is it only certain breeds or can they be any breed with right breeding done over generations. Does a black SL and a red SL make more SLs?
     
  2. Krys109uk

    Krys109uk Chillin' With My Peeps

    Sex links are made by knowing & using the genes which are known to be on the Z sex chromosome. With aves it is the male who is homogametic. i.e. he has both sex chromsomes the same, ZZ, the female only carries one Z chromosome & a w. The sex chromosome inherited from the mother determines the sex of the chick. Chicks inheriting a Z chromosome from the mother will be a male; the chick inheriting a w from the mother will be a female (& the father upplies the other Z chromosome).
    So if one uses a female with a dominant trait which is known to be carries on the Z chromosome, (such as sex linked barring, Sex linked silver, Inhibitor of dermal melanin, slow feather growth & others). And use a male carrying the recessive allele (possible gene for one position, or locus) on both of his Z chromosomes. The mother will pass on the dominant trait, on her Z chromosome to her male offspring, the female offspring will not inherit the trait because they inherited a w which does carry the gene for the trait. Thus the dominant trait is only observed in the males enabling people to determine which chicks are males & which are females.
     
  3. Sonoran Silkies

    Sonoran Silkies Flock Mistress

    20,149
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    Jan 4, 2009
    Tempe, Arizona
    No. (to black + red)

    How much basic genetics do you understand? Learn correct terminology first. It makes understanding explanations quite a bit easier.

    The sex chromosomes are different lengths for male versus female. With humans, males are XY and females are XX. With chickens (I believe all birds, but am not 100% certain of this) males are ZZ and females are ZW.

    The W chromosome is shorter than the Z chromosome, so some of the genes that occur on the Z chromosome do not occur on the W chromosome. For these genes, females only have one copy as they only have one Z chromosome, whereas males have two copies as they have two Z chromosomes.

    When the birds mate and an egg becomes fertile, each parent contributes chromosomes to the egg. For the sex chromosome, the male always contributes a Z chromosome, because that is what he has. The hen, on the other hand contributes either Z or W.

    The eggs to which she contributes Z become her sons (Z from father + Z from mother: ZZ: male). Those to which she contributes W become her daughters (Z from father + W from mother: ZW: female). Thus, any genes that are only on the Z chromosome are only contributed to her sons; her daughters receive only a single copy, and it comes from their father. Some of these genes are not particularly useful in determining gender of a newly hatched chick, but several are.

    The S gene is one of these, and is used in creating red sex-links (also called sil-go-link). Females can only be silver or gold (the two alternatives, or alleles, of this gene). Males can have two copies of silver, two copies of gold or one copy of each.

    For creating a red sex-link, you mate a white (S, aka silver, the dominant allele) hen to a red (ss, aka gold, the recessive allele) cock. The hen gives her copy of the dominant allele to her sons, and no copy to her daughters. The cock gives a copy of his recessive allele to all his offspring.

    The resulting sons inherit a dominant allele from their mother and a recessive allele from their father--they will display the trait (plumage colour) inherited from their mother as it essentially overrides the gene inherited from the father.

    The daughters, on the other hand inherit only the recessive allele from their father. Since it is the only copy of the gene present, it displays, and their plumage is coloured the same as their father's.
     
  4. Zahboo

    Zahboo Simply Stated

    Feb 3, 2009
    Hope Mills, NC
    Thanks...

    If you breed an EE to a barred rock roo, will it produce a sexlink, feed store said yes, but IDK
     
  5. Krys109uk

    Krys109uk Chillin' With My Peeps

    If you breed an EE to a barred rock roo, will it produce a sexlink, feed store said yes, but IDK

    No....they've got mixed up.
    Depending upon the colour of the EE, it could work the other way round, with a barred rock hen & EE cock bird.​
     

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