DEFINITION

 

Genetics is the science of heredity. It studies the hereditary characteristics of individuals, their transmission through generations and their variations (mutations).
Its main objective is to explain how character traits and various qualities are transmitted from
parents to their descendants.

 

 

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DNA

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These transfers are developed from genes, composed of fragments of deoxyribonucleic acid or DNA, the molecule responsible for coding the genetic data present in cells.
DNA associated with proteins forms highly organized structures called chromosomes. It is the support of genetic information; it allows the development of molecular genetics and the diversification of cells.

 

 

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GENOTYPE

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The set of genes of a person (or a living organism) is called genotype.
The phenotype is the visible expression of the genotype.
It is the visible character given by a gene.

 

 

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TRANSMISSION
 

Each parent transmits to the child a half of genome.
Every human being with parents has therefore a double set of chromosomes on which are the genes.
So each gene exists in duplicate in each cell, one is the version of the mother, the other the version of the father. These are called alleles.

In an autosomal recessive disease, each parent passes on one copy of a defective gene.
The parents are not sick because their other copy takes over.
On the other hand, the child who has both copies mutated is sick.
If both alleles are healthy but slightly different, there are two cases: either each gene is expressed, or only one is expressed (dominant) and the other is silent (recessive).

 

 

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PHENOTYPE
 

A gene is the code for a protein. Once expressed in the cell, this protein gives a characteristic to the organism, a phenotype.
This characteristic is most often a visible element (size of fingers, colour of eyes, shape of the head).
The phenotype is the visible expression of the genotype, it is the visible character given by a gene.

 

 

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Genetics therefore analyses the transmission of biological heritage from one individual to
another.

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DNA structure and composition - DNA sequencing - Gene-protein correlation