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| Duplication of DNA |
When a cell reproduces, each daughter cell needs a copy at the parent cell's genetic information so that it will be able to synthesize the proteins necessary, to build cellular parts and carry on metabolism.
DNA molecules can be duplicated (replicated) and this duplication takes place during the inter-phase at the cell's life cycle. As the duplication process begins, bonds are broken between the complementary base pairs of the double strands in each DNA molecule. Then the double-stranded structure pulls apart and unwinds, exposing the organic bases of its nucleotides.
New nucleotides of the four types found in DNA pair with the exposed bases, and enzymes cause the complementary, bases to join together In this way a new strand of complement an nucleotides is constructed along each of the old strands. As a result, two complete DNA molecules are produced, each with one old strand of the original molecule and one new strand. During mitosis, these two DNA molecules held within chromosomes are separated so that one passes to each of the newly forming daughter cells.
Changes in Genetic Information
The amount of genetic information held within a set of human chromosomes is very large In fact, some investigators estimate that it may equal the amount of the text held within 20 sets of encyclopaedia Britannica. Since each of the trillions of cells in an adult body resulted from mitosis, this large amount of information had to be duplicated many times and with a high degree of accuracy. However, occasionally a mistake occurs or the DNA structure is damaged. and the genetic information is altered Such a change is called a mutation, and if the cell in which it occurs survives. the mutation is likely to be passed to future generations of cells.
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