Basic Genetic Terminology
Genetics is the study of heredity and the variation of inherited characteristics. In the context of animal breeding and genetics, understanding basic terminology is crucial for anyone looking to work in this field. This section will cover key terms and concepts that form the foundation of genetic understanding.
Key Terms
1. Gene
A gene is the basic unit of heredity. It is a segment of DNA that contains the information necessary to produce a specific protein or set of proteins. Genes are located on chromosomes and can influence various traits in an organism.Example: In dogs, a gene may determine coat color. The alleles for this gene can result in different coat colors such as black, brown, or golden.
2. Allele
An allele is a variant form of a gene. For any given gene, an individual may inherit two alleles, one from each parent. Alleles can be dominant or recessive.Example: The gene for coat color in dogs has two alleles: one for black (B) and one for brown (b). Black is dominant over brown, meaning that a dog with at least one B allele will have a black coat.
3. Genotype
The genotype is the genetic makeup of an individual, representing the combination of alleles inherited from the parents.Example: A dog with a genotype of BB or Bb will have a black coat, while a dog with a genotype of bb will have a brown coat.
4. Phenotype
The phenotype is the observable physical or biochemical characteristics of an organism, determined by both its genotype and the environment.Example: The phenotype of a dog could be its coat color, size, or behavior. A dog with the genotype Bb will have the phenotype of a black coat.
5. Homozygous and Heterozygous
An individual is homozygous for a gene if it inherits the same alleles from both parents (e.g., BB or bb). An individual is heterozygous if it inherits different alleles (e.g., Bb).Example: A dog with genotype BB is homozygous dominant, while a dog with genotype Bb is heterozygous.
6. Dominant and Recessive Traits
A dominant trait is expressed in the phenotype even when only one allele is present. A recessive trait is only expressed when an individual has two copies of the recessive allele.Example: In our dog coat color example, the black coat (B) is dominant, while the brown coat (b) is recessive. Therefore, only a dog with the genotype bb will display a brown coat.