Introduction

• Gene theory is one of the basic principles of biology. It is the idea that genes are the basic units of heredity in which characteristics are passed from one generation to the next.

• Genes are located on chromosomes and consist of DNA.

• They correspond to a region of the DNA that influences the form or function of an organism in specific ways.

• The result of such influence is the phenotype (visual appearance), whereas the complete assembly of genetic information is called genotype.

• DNA - Transcription - RNA - Translation - PROTEIN = PHENOTYPE

The cell theory states that the cell is the fundamental unit of life, and that all living things (except viruses) are composed of one or more cells or the secreted products of those cells.

The generally accepted parts of the cell theory include:

• The cell is the fundamental unit of structure and function in all living organisms.

• All known living things are made up of one or more cells.

• All cells arise from pre-existing cells by division.

• Energy flow occurs within cells (metabolism and biochemistry).

• Cells contain hereditary information (DNA) which is passed from cell to cell during cell division.

• All cells are basically the same in chemical composition in organisms of similar species.

• The activity of an organism depends on the total activity of independent cells.

• The theories of modern biology include cell theory, gene theory, the theory of evolution by natural selection as well as the theory of homeostasis.

Central concept of biology that states that:

• life changes and develops through evolution

• all life forms come from a common origin

The ability of an organism to regulate its internal environment to maintain a stable condition.