Editing Labrador Retriever (section)

=== Colour ===
{{Main|Labrador Retriever coat colour genetics}}
[[File:3labradorcols.jpg|thumb|alt=three Labrador retrievers: Yellow, black, and chocolate|The three colour varieties, from front to back: Yellow, black, and chocolate]]

Labradors are registered in three colours: Solid ''black'', ''yellow'' (anything from creamy white to fox-red), and ''chocolate'' (medium to dark brown; originally called "liver").<ref>
{{cite web
 |title=Breed colours
 |website=thekennelclub.org.uk
 |publisher=[[The Kennel Club]]
 |url=http://www.thekennelclub.org.uk/services/public/breed/colours.aspx?id=2048
 |access-date=10 January 2015 |url-status=dead
 |archive-url=https://web.archive.org/web/20150110200738/http://www.thekennelclub.org.uk/services/public/breed/colours.aspx?id=2048
 |archive-date=10 January 2015
}}
</ref>

Puppies of all colours can occur in the same [[Litter (animal)|litter]]. Coat colour is determined primarily by three genes, called [[Melanocortin 1 receptor|''MC1R'']], [[Agouti coloration genetics|''Agouti'']], and ''CBD103''. If a dog carries [[Wild type|wild type alleles]] at all three loci, the dog will have a yellow coat. If a dog has a loss-of-function mutation at MC1R, it will also have a yellow coat, regardless of the genotypes at the other two loci. Dogs carrying wild-type alleles for MC1R and Agouti, together with the black allele of CBD103, will have a black coat.<ref name=Candille-Kaelin-etal-2007>
{{cite journal
 |last1=Candille   |first1=Sophie I.    |last2=Kaelin  |first2=Christopher B.
 |last3=Cattanach  |first3=Bruce M.     |last4=Yu      |first4=Bin
 |last5=Thompson   |first5=Darren A.    |last6=Nix     |first6=Matthew A.
 |last7=Kerns      |first7=Julie A.     |last8=Schmutz |first8=Sheila M.
 |last9=Millhauser |first9=Glenn L.     |last10=Barsh  |first10=Gregory S.
 |year=2007
 |title=A β-defensin mutation causes black coat colour in domestic dogs
 |journal=[[Science (journal)|Science]]
 |volume=318  |issue=5855  |pages=1418–1423
 |pmid=17947548  |doi=10.1126/science.1147880
 |bibcode=2007Sci...318.1418C  |pmc=2906624
 | issn=0036-8075}}
</ref>{{efn|
"Production of yellow versus black pigment in dogs is controlled by three genes: MC1R, Agouti, and CBD103. Dogs carrying wild-type alleles for all three genes have a yellow coat resulting from Agouti antagonism of MC1R signaling in melanocytes (yellow Great Dane, top). Dogs carrying a loss-of-function mutation at MC1R have a yellow coat, regardless of their genotype at Agouti or CBD103 (yellow Labrador retriever, middle). Dogs carrying wild-type alleles for MC1R and Agouti, together with the dominant black allele of CBD103 (KB) have a black coat resulting from the interaction between a β-defensin and MC1R (black Curly Coated Retriever,{{nobr| bottom)." — Candille, Kaelin, ''et al.'' (2007)<ref name=Candille-Kaelin-etal-2007/>}}
}}

According to a 2011 study, 13 out of 245&nbsp;Labradors studied were [[heterozygous]] for the M264V mutation responsible for the [[melanistic mask]], and one was [[homozygous]]. Within this breed, the trait cannot be determined simply by appearance.<ref>
{{cite journal
 |last1=Conant  |first1=E.K.
 |last2=Juras   |first2=R.
 |last3=Cothran |first3=E.G.
 |year=2011
 |title=Incidence of the mask phenotype M264V mutation in Labrador retrievers
 |journal=Research in Veterinary Science
 |volume=91  |issue=3  |pages=e98–e99
 |doi=10.1016/j.rvsc.2011.02.002  |pmid=21353269
}}
</ref>
[[File:ChocolateLabPup.jpg|thumb|The most common places where pigmentation is visible are the nose, lips, gums, and the rims of the eyes.]]