Basics ofD og Breeds and M odern D og Breeding Goals Review ofgenetic term inology Prim ary know n genes controlling coat color and color patterns Epistasis G enotypes and phenotypes for coat colors in various breeds ofdogs From: The Ultimate Dog Book Genetic Basics Chrom osom es ♦ DNA ♦ 78 chrom osom es in dom estic dog ♦ autosom alal-38 pair ♦ sex chrom osom es 1 pair -XX,XY ♦ gam etes Genetic Basics Chrom osom es ♦ genes -proteins, gene regulation ♦ locus/loci ♦ alleles -“m utations” ♦ hom ozygous, heterozygous ♦ linkage Genetics Basics Traits -qualitative,quantitative (polygenic),sex lim ited G ene action ♦ dom inant/recessive -A /a ♦ incom plete dom inance ♦ additive ♦ epistasis 1 Example of Additivity Example of Epistasis Three loci believed responsible for color in these M iniature Pinschers Four alleles for spotting m ay act additively to produce gradations ofspotting Genetics Basics M odifier genes G enotype -determ ined atfertilization Phenotype = genotype + environm ent ♦ influenced by gene action dom inance/recessive, additivity, y, epistasis, s,m odifiers ♦ e.g.black dogs Agouti – agouti color Tw o ofthese genes are acting epistatically in the brow n dog Coat Color Genetics in Dogs Prim ary,recognized genes controlling coatcolor -eum elanin (dark), phaeom elanin (tan) ♦ G -graying ♦ A -agouti ♦ M -m erle ♦ E – extension ♦ R -roaning ♦ K – black ♦ T -ticking ♦ B -brow n ♦ S -w hite ♦ C -albino spotting ♦ D -blue dilution Agouti color Basic color ofm any w ild anim als Cam ouflage Patterns on individualhairs and over the body Stripes or banding on individualhairs dark – often near hair tips Pattern over the body 2 Basis of Color Basis of Pattern M elanin – produced by m elanocytes D istribution ofcolor on body eum elanin (dark – black or brow n) M odifiers phaeom elanin (cream ,tan,or red) Presentation Agouti Locus in Dogs A lleles for th e agoutilocus D esig n ation Sym bol (Solid black A s) D om in an tyellow Ay A g outi(w olf) Aw Saddle asa B lack an d tan at R ecessive black (Sh eph erds,S.sh pdog ) K (dominant) Black Locus in Dogs Agouti Locus in Dogs Airedale - asa asa a K Locus in Dogs Brindle Great Dane Epistatic to A ,B and E loci K = dom inantblack kbr = brindle k = norm al Rottweiler - at at Black Labrador kbr_ KK 3 Brindle Coat Color in Dogs Several theories have been proposed Ebr E locus as Tabby (Ta (Ta)) as in cats br ♦ K, K , k ♦ experimental evidence in greyhounds seems to corroborate the existence of a separate locus - (K) ♦ ♦ Extension Locus in Dogs Epistatic to A and K loci G reatdisagreem entover alleles for E locus -early w ork lists three or four Early w ork does notagree w ith results in other m am m als;recentm olecular w ork seem s to indicate only E and e Brindle Coat Color in Dogs Great Dane Kbr_ Greyhound Kbr_ Extension Locus in Dogs Irish Setter K_B_ee Bracco Italiano K_bbee E_ ⇒ norm alA locus expression ee ⇒ A y,asa,at resultin red/yellow Brown Locus in Dogs Albino Locus in Dogs Brow n locus in dogs -B,b Principle influence on phaeom elanin Eum elanin pigm entgranules in bb dogs are sm aller and m ore round influences the perceived color O nly a few albino alleles in dogs Little to no effecton phaeom elanin B_ dogs are black bb hair and nose leather,dogs are liver or chocolate A lleles for th e albin o locus D esig n ation Sym bol Fullcolor C C h in ch illa,silver (lig h ten s tan ) B lue-eyed albin o A lbin o cch cb c 4 Dilution Locus in Dogs Albino Locus in Dogs Golden Retriever cchcch Weimaraner Dilution Locus in Dogs bbddK_ bbddK_ Influences dispersion ofpigm entgranules -both pigm ents A lleles for the dilution locus D esignation Sym bol Black _ _B_D _K_ Blue _ _B_ddK _B_ddK _ Black and tan atatB_D _kk Chocolate and tan atatbbD _kk Lilac and tan atatbbddkk Graying Locus in Dogs N otw ellunderstood A nim als are born w ith norm alcolor and lighten w ith age -prem aturely Miniature Pinscher atatB_D_kk atatbbddkk Believed to be presentin Poodles, O ld English Sheepdogs,and terriers Incom plete dom inance -additivity? y? ♦ G G -extrem e lightening ♦ G g -slightlightening Graying Locus in Dogs Merle Locus in Dogs Kerry Blue Terrier K_G_ Incom plete dom inance Causes patchy dilutions in coatand eye colors A dditive gene N orm aldogs -m m H om ozygous M M dogs often have abnorm alities such as deafness, blindness,sm alleyes -recom m ended to avoid m ating tw o m erles 5 Harlequin Locus in Dogs Merle Locus in Dogs Harlequin animals mated to nonnonHarlequin results in 50% normal & 50% Harlequin Cardigan Welsh Corgi asa asa Mm Harlequin animals mated to Harlequin animals results in 67% Harlequin , 33% normal Why? Harlequin Locus in Dogs In merle animals, H allele causes merle areas to become white H allele thought to be present in a few breeds - Great Danes, some collie types Harlequin Locus in Dogs Great Dane D_K_HhMm Homozygous HH is lethal in the embryonic stage - avoid mating two harlequins Sampling of Coat Colors in Great Danes Ay_D_kkhhMm Roan Locus in Dogs ddK_hhmm Australian Cattle Dog R_ D_K_HhMm Disagreement about whether R is a distinct locus May represent extreme ticking Ay_D_Kbr_hhmm Ay_D_kkHhMm 6 Spotting Locus in Dogs Spotting Locus in Dogs Percent white probably influenced greatly by modifier genes S – solid color, no white A lleles for th e spottin g locus D esign ation Sym bol Self– n o spottin g S Irish spottin g si Piebald spottin g sp Extrem e spottin g sw Spotting Locus in Dogs si – Irish allele (from Irish rat) few definitely spotted areas sp – piebald 1515-20 % of coat solid (pigmented) sw – extreme piebald, virtually no spotting, i.e. solid white Ticking Locus in Dogs White areas have flecks of color Most dogs are tt S=0 si = 11-3 sp = 33-9 A lleles for the ticking locus D esignation Sym bol Ticking T N o ticking t sw = 99-10 Ticking Locus in Dogs White Coated Dogs German Shorthair Pointer bbK_spspTT Dalmation B_K_ggswswTt Likely caused by different allelic combinations in different breeds swsw - Samoyed, Bull Terrier, Great Pyrenees, Sealyham Terrier ♦ Ay_cchcchee - West Highland Terrier ♦ MM - collies, etc. - but other abnormalities present frequently ♦ w - proposed allele in Siberians ♦ 7 White Coat Color in Dogs West Highland Terrier Ay_cchcchee Great Pyrenees - Genes Affecting Coat Texture Numerous other genes are involved with coat texture. A few include: L – short hair, l – long hair Wh – wire hair, wh – normal hair ♦ K – normal coat, k – kinky coat ♦ Wo – normal coat, wo – whorled ♦ K_eeswsw ♦ Hairless Loci in Dogs Genes Affecting Coat Texture Mexican Hairless Hairlessness: different loci ♦ HrHr Mexican hairless – Hr normal – hr breed, most hairless breeds have this mutation older ♦ American hairless – ha normal – Ha American Hairless Terrier haha Take Home Points Take Home Points “normal dog” All dogs possess various genes presented for coat color, texture, etc. When breeds do not express a given pattern, the “normal” allele probably is fixed Several alleles are lethal or semisemilethal when homozygous - MM, HH Breeders should avoid matings that can produce the lethal homozygotes awawBBCCDDEEkk 8 Take Home Points Be aware of loci important for individual breeds to produce desired coat characteristics through mating. Off color dogs may indicate parentage is questionable; other factors may also play a role – mutation rate, low frequency of recessive allele Molecular genetics can provide great insight From: The Ultimate Dog Book 9
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