Gene
Section of the DNA molecule, representing the smallest structural and functional unit of hereditary information

Chromosome (Genotype)
Dense structures that are formed in the final coiling stage of chromatin and could be observed under a microscope during the metaphase of cell division. Each organism type has its specific genetic program, encoded in a number of chromosomes with specific structure. The number, the form, and the size of the chromosomes in cells of one specific type are its characteristic distinctive feature and are called a complete set of chromosomes or a karyotype. Each human cell has 46 chromosomes, arranged in 23 chromosome pairs.

Karyotype
Numeral and morphological characteristic of the chromosomes

Recessive gene
A hidden gene that could not be expressed in the phenotype in the presence of a dominant gene. This gene could be expressed only in combination with the same recessive gene from the other parent.

Dominant gene
A gene that is fully expressed in the phenotype, regardless of the presence or not of recessive genes

Locus
The place of each gene in the chromosome

Homozygous
BB or bb (two identical dominant genes or two identical recessive genes)

Heterozygous
Bb (a combination of one dominant and one recessive gene)

Zygote
A fertilized egg cell

Gametes
Reproductive cells

Phenotype
The composite of all observable characteristics or traits of a specific organism, resulting from the expression of specific genotype (genetic program) and the influence of environmental factors; i.e. the physical expression of a chromosome

Genotype
The specific genetic identity of an organism that does not have an outside expression, i.e. the specific genetic constitution of the organism

Trait
Observable expressions of the genes (a phenotypic characteristic) of an organism that are copied and passed down to the successive generations in the reproduction process in a way determined by environmental factors

Acquired traits
Result of the transfer of genes: between the populations, e.g. in case of migration, or between species, in case of horizontal gene transfer (HGT)

Mutation
A change of the nucleotide sequence of the genome of a cell caused by radiation, viruses, transposable elements and chemical mutagens, or may result from errors in the process of DNA replication or meiosis. Genes that have undergone mutation lead to changes in the nucleotide sequence. These changes can either have no effect, or alter the product of the respective gene, or prevent the gene from functioning properly or completely. When the mutation leads to establishment of new traits or to a change in the old ones, the organisms get inheritable changes.

Meiotic division
Reduction (decrease) of the heritable information

Allele
One of a number of alternative forms of the same gene in one of the chromosomes determining various phenotypic traits. Alleles are also called the alternative functional states of the genes. They are either dominant (B) or recessive (b).

Genetic algorithms
GA is a class of heuristic search methods

Population
A group of individuals. The more diverse are the traits of the individuals in the group, the greater the possibility is for “survival” of the population in case of change in the environmental conditions.

Evolution
The process of growth, change or development. In biology evolution is the change in the inherited characteristics (traits) of a biological population over successive generations. It occurs when these heritable differences become more or less common in the population: nonaccidentally – as a result of the natural selection, or accidentally – in case of genetic drift.

Natural selection
A biological process, in which the inherited traits, advantageous for the organisms, become more common in each successive denegation of a population, while the disadvantageous traits – less common, due to differential reproduction of the genotypes of the bearers. This happens because the organisms possessing favourable genes pass to the next generation more copies of their traits. Over the successive generations adaptations occur by combinations of successive, small, random changes in the traits, and via the natural selection of the variants that have become most adapted to the environment.

Genetic drift
Unlike the NS, it leads to random changes in the frequency of a gene variant in a population. Genetic drift is a result of the role that the chance has in determining whether a given individual survives and reproduces.