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How hereditary factors are transmitted

In each cell there is a nucleus with all the hereditary information of the individual. The genes in the nucleus has the shape of a helix, a double spiral. The spiral consists of two very long DNA molecules (Nuclear-DNA) which contains nuclear genes. Half of the DNA has been inherited from the father and the other half from the mother.
DNA is also present in the cell energy package, the mitochondrion (mtDNA), which influences the energy turnover. MtDNA is only inherited from the mother because the offspring receive their mitochondria from the mother's egg. Thus all the decendents of a female have the same mtDNA for a long chain of generations.