Grille Penneta was proposed by the English scientist Penneta to facilitate the solution of practical problems in genetics.When it comes to a criterion on which the study is conducted, you can try to create a diagram-drawing or count options in mind.But if we study two or more signs, circuit full of strange symbols, and remember all the combinations is simply impossible.In such circumstances, the lattice Penneta - a great way to streamline decision.
Based on the known laws of genetics, we know that every quality characteristic of any organism is encoded in the DNA.Plot its molecules are responsible for such indication - gene.Since every cell of the body has at its core a double set of chromosomes, it turns out that one sign of a single gene is responsible, but it is present in two forms.They are called alleles.Knowing that in sexual reproduction cell (gamete) contains a set of chromosomes, divided into two, and bearing in mind how these cells are formed in the body, we understand that every such germ cell gets one or the other allele.Lattice Penneta captures all the possible types of gametes from each parent.Their record over her crossing from one participant and a party (usually the left) - on the other.In the cell, column and line of intersection we find a combination of genes descendants who will determine exactly how he manifested a particular trait.
What are they
principle of construction of these tables is the same, but generally decided to allocate the following types of arrays Penneta:
- vertical-horizontal;
- inclined.
This first version is built like a regular table with columns and lines, and the second is a diamond on the upper side edges which are written designation possible parental gametes.Using the second type is rare.
Practical application
As already mentioned, the lattice Penneta used to solve problems.It is a good graphical method that allows you to calculate the resulting offspring by any number of attributes.The principles of the solution of any problem in the genetics can be formulated as follows: determine how each gene is designated.We find out the parental genotypes (combination of genes) that determine which sex cells can be formed from each parent body.Enter data into the lattice Penneta, we find all the possible genotypes of descendants.On them you can navigate, how it will look each of the resulting organisms.
very simple example: the hair length genes in cats denote them G and g.Spending mating short-haired cats, long-haired cat.Longhair gene is recessive, which means it occurs only in the homozygous state, that is, our cat can have only genotype gg.But cat can be both Gg, and GG.That we can not say in appearance (phenotype), but we can conclude from it if the cat with long hair had been born the same as he, kittens, her formula - Gg.Let it be.Here is a simple lattice:
| types gametes | G | g |
| g | Gg | gg |
| g | Gg | gg |
We got that 50% of cats have long hair like his father.And the other half of their short-haired, long-haired but carry the genes, their genotypes are the same as the mother.
