Genetics is the study of hereditary (the passing of traits from parents to offspring) and the variation of inherited characteristics. We can use genetics to predict what future generations will be like and diagnose genetic diseases. All of this is because of genes. Genes are like computer codes inside the human body that is used to program different variations of a trait. Like how genes are individual codes, the genotypes are entire programs. More specifically, they are the genetic makeup of the organism and describes the patterns of genes and alleles (one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome) that are present in the chromosomes (a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes).
Gregor Mendel (above) is seen as the father of genetics. He was inspired by how pea plants grew different colored flowers.
The way we predict potential genotypes is through a punnet square,a tool that can be used to show all of the potential genotypes and phenotypes (what we see physically expressed) an offspring can display, and is based off of the parental genotype. In a punnet square, genotypes consist of two letters, one being dominant (always masks a recessive gene, meaning that even if the recessive form of the trait is present, it will not be observable), shown as a capital, and the other being recessive (requires two recessive alleles to become recessive genes), shown in lowercase. Just because someone has a dominant allele doesn't mean that the recessive gene won't show up again. Mendel's proposition of dominance tells us that recessive traits can still be present, even if they aren’t displayed, and they can show back up in the next generation if combined with another recessive form of the trait.
In the above punnet square, there is 25% homozygous dominant, 25% homozygous recessive, and 50% heterozygous.
Whenever there is two of the same alleles (letters) the are either homozygous recessive, with both letters in lowercase, or homozygous dominant, with both letter capital. When there are one of each allele in the gene, it is heterozygous.
Some dogs are specially bred for specific traits.
When you breed animals for specific traits, you could do it through monohybrid to breed for one trait, or dihybrid to breed for two traits.