Before an individual undertakes the goal of trying to develop certain traits and characteristics through breeding, it is necessary to lay some foundations for understanding the genetic process. The basics need to be understood before we can deal with how features are passed from one generation to the next.
The first thing we have to do is get some terms down. Without a working vocabulary, we will never know what anyone else is talking about.
The most basic genetic term is the gene. A gene is a sequence of DNA that code for traits or features. They are attached together in a structure called a chromosome. Chromosomes, in turn, are linked together to form a DNA strand.
Different genes behave differently in their potency. By this I mean that a feature can be “activated” in some cases by the presence of a single gene, in other cases by the presence of a gene pair. These genes are said to act in a major manner. Examples of these are body and fin shape.
In other cases features are dependent on the cumulative effect of several genes. These features are called polygenic. Body size is an example.
There is also a gene called a modifier gene which alters a major gene action. For example, color and fins are controlled by a single gene or gene pair, but they can be affected by other genes in that the size of the fins and the depth of the color can be altered.
Guppy Sex also has a determining factor in genetics. Traits or features which are related to the sex of the guppy are said to be sex-linked. Other than the obvious trait of male/female, some colors and fin types are subject to sex-linked genes. Most traits, however, are inherited regardless of which sex passes them to the offspring.