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brainswax

Amateur goater

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Goat Genetics

Goat Pattern Genetics

  1. The base pattern is dictated by the Agouti locus
    • Controls the distribution of black-based (or dark) and tan-based (or light) areas
  2. Each animal inherits one, and only one, base pattern from each parent (making a pair of genes)
  3. Black is recessive
    • Both parents must carry black to produce a black kid
    • If the animal carries only one black pattern, then only the other pattern will be expressed
  4. Light areas are dominant over dark areas
    • Codominant patterns will only show dark where both inherited patterns are dark
    • If the animal carries the gold pattern, then only gold will be expressed
  5. The light color can range from white, cream, gold, tan to red (i.e. a gold pattern goat could be colored white)
  6. Mutations can, although very rarely, cause patterns that neither parent carry

Base Colors

There are two types of pigments determining color. All colors are some variation of one of these pigments (or white in the absence of pigment):

  1. Eumelanin - black
  2. Pheomelanin - red

Base Patterns

The pattern is determined by the Agouti locus, referred to by the ‘A’ symbol, which determines the distribution of dark (eumelanin) and light (pheomelanin) areas on the animal. Each animal will inherit one of the following alleles from each parent (there are more, but these are the most common in Nigerian Dwarf):

Pattern Allele Dominance
Gold (White) Awt Dominant
Buckskin (San Clemente) Asc Codominant
Chamoisee (Black Belly) Ab Codominant
Swiss Marked Asm Codominant
Cou Clair (Peacock) Apk Codominant
Sundgau (Black & Tan) At Codominant
Bezoar A+ Codominant (wild type)
Caramel Acr Codominant
Red Cheek Arc Codominant
Black a (or Aa) Recessive

Modifiers

Patterns and colors can inherit independent modifiers from each parent:

Locus Name Color/Pattern Dominance Effect
B Brown Chocolate Bd (dark brown) > Bl (light brown) > B+ (wild type, neutral) > br (brown) Produces brown pigment in black areas.
C Chincilla Albino ? Unknown. May be responsible for color dilution.
D Dilution Muted D (not diluted) > d (diluted) Recessive dd turns black to grey/blue in mammals
E Extension Red Ed (black) > E+ (wild type, neutral) > er (red) Dominant black or turns black to red or yellow. Most are neutral wild type.
S Spotted Spotted S (spotted) > s (not spotted) Produces random white spots. Can cover entire body.

Additional Modifiers

  • Blue eyes (dominant)
  • Polled (dominant)
  • Moon spots (dominant)
  • Roaning (dominant) - it’s believed to be a partial dominant trait, but locus is unknown

Terminology

  • Allele - a variation of a gene
  • Codominant - when two dominant alleles can express together
  • Diploid - an animal that has two copies of each chromosome; one from the mother and one from the father
  • Dominant - an allele is considered dominant if it can be expressed in an animal that only has one copy of the allele
  • Epistatic - a gene that changes the expression of another (hypostatic) gene at a different locus
  • Express - when a trait is visible on the animal
  • Gene - a sequence of one or more nucleotides in a DNA molecule that makes up a basic unity of heredity
  • Genotype - the type, or allele, for a gene
  • Heterozygous - when the alleles in a pair of genes are different
  • Homozygous - when the alleles in a pair of genes are the same
  • Hypostatic - a gene that expresses a different phenotype depending on another (epistatic) gene
  • Incomplete Dominance - or partial dominance, when a dominant allele doesn’t completely mask a recessive allele and creates a blended phenotype
  • Linkage - when two genes are near each other and tend to inherit together
  • Locus - the location of a gene
  • Loci - plural of locus
  • Mendelian Inheritance - usually refers to single-gene, single-trait inheritance
  • Phenotype - a visible trait
  • Pleiotropic - when a single gene affects multiple phenotypes
  • Polygenic - when multiple genes interact to produce a phenotype
  • Recessive - an allele is considered recessive if it can only be expressed when both alleles in a gene are the same (homozygous)
  • Wild Type - a wild type allele is considered the non-mutated, or wild, variation of a gene

Sources