The Penett Grid is a simple solution for complex problems

The Penet lattice was proposed by the English scientist Pennet to facilitate the solution of practical problems in genetics. When it comes to one feature, which is being studied, you can try to create a diagram-drawing or to calculate possible options in the mind. But if two or more features are studied, the schemes are full of strange notation, and it is simply impossible to remember all the combinations. In such circumstances, the Pennet grid is a great way to streamline the solution.

Based on the known laws of genetics, we know that every qualitative sign of any organism is encoded in DNA. The site of its molecule, responsible for one such feature - gene. Since any cell in the body has a double set of chromosomes in its nucleus, it turns out that one gene is responsible for one attribute, but it is present in two forms. They are called alleles. Knowing that during sexual reproduction the cell (gamete) contains a set of chromosomes divided by two, and remembering how these cells form in the body, we understand that one or another allele of the gene enters each of these cells . The Penet lattice records all possible types of gametes from each parent. They are recorded over it from one cross member and from either side (usually left) - from the other. In the cell of the intersection of the column and the line, we find a combination of the genes of the offspring, which will determine how exactly this or that feature will manifest itself.

What are they like?

The principle of constructing these tables is the same, but in general it is customary to distinguish the following Types of Pennet gratings:

• Vertical-horizontal;
• Inclined.

In this case, the first variant is constructed in the same way as a regular table with columns and lines, and the second is a rhombus with the names of possible parental gametes written along the upper lateral edges. Use of the second type is rare.

Practical use

As already mentioned, the Penet lattice is used to solve problems. It is a visual graphical method that allows you to calculate the resulting offspring by any number of characteristics. The principles of solving any problem for genetics can be formulated as follows: we determine how each gene will be designated. We find out the parental genotypes (combinations of genes), determine which sex cells can be formed in each parental organism. We enter data into the Penet lattice, we find all possible genotypes of descendants. They can be used to determine how each of the resulting organisms will look.

A very simple example: genes of fur length in cats, we denote them by G and g. We cross a short-haired cat and a long-haired cat. The longhaired gene is recessive, which means that it manifests only in the homozygous state, that is, our cat can only have a genotype of gg. But the cat can be either Gg or GG. We can not say this from the exterior (phenotype), but we can conclude that if the same kittens were born from a cat with a long coat, then its formula is Gg. Let it be. And here is the simplest lattice:

We got that 50% of kittens have long hair, like a father. And the other half of them are short-haired, but carry genes of long-haired, their genotypes are the same as those of the mother.