Introduction to genetics: Difference between revisions

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Genes are copied each time a cell divides into two new cells. The process that copies DNA is called [[DNA replication]].<ref name=nih/> It is through a similar process that a child inherits genes from its parents when a copy from the mother is mixed with a copy from the father.

DNA can be copied very easily and accurately because each piece of DNA can direct the creationassembly of a new copy of its information. This is because DNA is made of two strands that pair together like the two sides of a zipper. The nucleotides are in the center, like the teeth in the zipper, and pair up to hold the two strands together. Importantly, the four different sorts of nucleotides are different shapes, so for the strands to close up properly, an '''A''' nucleotide must go opposite a '''T''' nucleotide, and a '''G''' opposite a '''C'''. This exact pairing is called [[base pairing]].<ref name=nih/>

When DNA is copied, the two strands of the old DNA are pulled apart by enzymes; then they pair up with new nucleotides and then close. This produces two new pieces of DNA, each containing one strand from the old DNA and one newly made strand. This process is not predictably perfect as proteins attach to a nucleotide while they are building and cause a change in the sequence of that gene. These changes in the DNA sequence are called [[mutation]]s.<ref>[http://learn.genetics.utah.edu/units/disorders/mutations/ Mutations] {{webarchive|url=https://web.archive.org/web/20080515113857/http://learn.genetics.utah.edu/units/disorders/mutations/ |date=15 May 2008 }} The University of Utah, Genetic Science Learning Center, Accessed 20 May 2008</ref> Mutations produce new alleles of genes. Sometimes these changes stop the functioning of that gene or make it serve another advantageous function, such as the melanin genes discussed above. These mutations and their effects on the traits of organisms are one of the causes of [[evolution]].<ref name=Marshall/>