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Chapter 24 : An Adventure in Dog Hair, Part II: Yellow Labs

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An Adventure in Dog Hair, Part II: Yellow Labs, Page 1 of 2

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Abstract:

This chapter highlights the need for the adventure in dog hair, in order to understand how the yellow color is produced. The pigments are synthesized in cells called melanocytes. The phaeomelanins are the family of red and yellow pigments. The exact color of the phaeomelanin depends on the enzymes available for its synthesis, as is the case with the color of the eumelanin (black or brown). In Labrador retrievers, the phaeomelanin is yellow. Yellow Labs are yellow because the receptor for melanocortin 1 (MC1) does not work, so even though the dogs' bodies produce MC1 and have functional genes for TYRP2 and TYRP1, the signal to produce the enzymes is never transmitted to the melanocyte. The gene that causes yellow coat color in Labrador retrievers is actually a nonfunctional allele of the gene for MC1R. Black and brown Labs have at least one functional allele, so their melanocytes receive the hormone signal to make TYRP2 and TYRP1. In the case of yellow Labs, the expression of the black or brown genotype is altered by the alleles of a completely separate gene. Geneticists call this phenomenon epistasis.

Citation: Kreuzer H, Massey A. 2008. An Adventure in Dog Hair, Part II: Yellow Labs, p 246-249. In Molecular Biology and Biotechnology: A Guide for Students, Third Edition. ASM Press, Washington, DC. doi: 10.1128/9781555817480_ch24

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Surface Receptors
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Figures

Image of Figure 24.1
Figure 24.1

In black and chocolate Labs, MC1 binds to its receptor, MC1R, signaling the melanocyte to produce TYRP2 and TYRP1. The melanocyte can then synthesize black or brown pigment.

Citation: Kreuzer H, Massey A. 2008. An Adventure in Dog Hair, Part II: Yellow Labs, p 246-249. In Molecular Biology and Biotechnology: A Guide for Students, Third Edition. ASM Press, Washington, DC. doi: 10.1128/9781555817480_ch24
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Image of Figure 24.2
Figure 24.2

In yellow Labs, the MC1R is nonfunctional. MC1 cannot bind to it, and the hair follicle melanocytes never receive the signal to synthesize TYRP2 and TYRP1. The melanocytes therefore do not synthesize black or brown pigment. Instead, dopaquinone is converted into yellow phaeomelanin.

Citation: Kreuzer H, Massey A. 2008. An Adventure in Dog Hair, Part II: Yellow Labs, p 246-249. In Molecular Biology and Biotechnology: A Guide for Students, Third Edition. ASM Press, Washington, DC. doi: 10.1128/9781555817480_ch24
Permissions and Reprints Request Permissions
Download as Powerpoint

References

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Possible gametes for parents with genotype BbRr

Citation: Kreuzer H, Massey A. 2008. An Adventure in Dog Hair, Part II: Yellow Labs, p 246-249. In Molecular Biology and Biotechnology: A Guide for Students, Third Edition. ASM Press, Washington, DC. doi: 10.1128/9781555817480_ch24
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Untitled

Citation: Kreuzer H, Massey A. 2008. An Adventure in Dog Hair, Part II: Yellow Labs, p 246-249. In Molecular Biology and Biotechnology: A Guide for Students, Third Edition. ASM Press, Washington, DC. doi: 10.1128/9781555817480_ch24
Generic image for table
Untitled

Citation: Kreuzer H, Massey A. 2008. An Adventure in Dog Hair, Part II: Yellow Labs, p 246-249. In Molecular Biology and Biotechnology: A Guide for Students, Third Edition. ASM Press, Washington, DC. doi: 10.1128/9781555817480_ch24

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