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American Hairless Terrier Genetics
The American Hairless Terrier is unique among all hairless dog breeds because it exhibits recessive hairlessness. Hairless parents can only produce hairless offspring. Other hairless dog breeds, Chinese Crested, Peruvian Inca Orchid, and Xoloitzcuintli, all have dominant hairlessness (see hairless breeds compare). For breeding with coated carriers, these tables are only predictions. You can never know for sure what Mother Nature decides to toss at you. She doesn't follow percentages. :o)
Gene - the functional and physical unit of heredity passed from parent to offspring; a small sequence of DNA determining certain characteristics, occupies a fixed position on a chromosome Allele - an alternate form of a gene, variants that occur at the same locus; one of the different forms of a gene that can exist at a single locus Chromosome - a rod-shaped structure in a cell nucleus carrying the genes that determine sex and the characteristics an organism inherits from its parents; chromosomes occur in pairs, one from the mother and a second from the father Locus - physical site or location of a specific gene on a chromosome Genotype - the actual alleles present in an individual dog; describes the genes of an AHT; hh, HH or Hh Phenotype - observable characteristics; describes the appearance of a trait; hairless or coated Dominant - producing the same phenotype whether its allele is identical (HH coated) or dissimilar (Hh coated carrier); the expression of a trait in the heterozygous condition, coated carrier (Hh) Recessive - a mode of inheritance in which a gene must be present from both parents for the trait to become manifested in an offspring; both parents must carry the recessive hairlessness gene (h) and pass it on to their pup (hh) Homozygous - having the same allele at the same locus on a chromosome; two recessive genes are paired (hh), or two dominant genes are paired (HH) Homozygous dominant - having dominant alleles at the same locus on a chromosome; coated (HH), no recessive genes Homozygous recessive - having recessive alleles at the same locus on a chromosome, this in the only time a recessive trait will be phenotypically (physically) seen; hairless (hh), no dominant genes Heterozygous - having different alleles at the same locus on a chromosome; a recessive (h) and a dominant (H) are paired (so the dominant trait is observed); coated carrier (Hh)
Case 1 Parents: Hairless x Hairless
Case 2 Parents: Hairless x Coated Carrier
Case 3 Parents: Hairless x Coated
Case 4 Parents: Coated Carrier x Coated Carrier
Case 5 Parents: Coated Carrier x Coated
Case 6 Parents: Coated x Coated
HL = hairless (AHT) Case 1
Case 2
Case 3
Case 4
Case 5
Case 6
Question from a visitor:
Reply: When a normal Rat Terrier is bred with a hairless AHT, the pups will be coated carriers ("coated AHT's"). They carry the recessive hairless gene, but they have hair themselves. Currently, AHTs are bred with excellent quality purebred Rat Terriers to enlarge and improve the AHT gene pool. This out-crossing to Rat Terriers will be stopped in the future once experts feel the AHT gene pool is diverse and large enough to support the breed. Rat Terriers have docked tails, but AHT's have full tails. Some AHT breeders leave their coated carriers undocked. This will visually separate them from Rat Terriers and identify them as coated carriers ("coated AHT's"). Rat Terrier breeders do not want coated carriers in their bloodlines. Coated carriers are bred with AHT's to create new AHT bloodlines. Sweet Lucy's 1996 - 2008 |
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Recessive Hairlessness