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[[Prokaryotic DNA]] is circular (a closed loop).  Whereas, [[eukaryotic DNA|eukaryotic chromosomes]] are linear (with ends), with the notable exception of [[Mitochondrial DNA]] and plastid (chloroplast) DNA, which is separate from the DNA in the nucleus<ref>Mitochondria and chloroplasts are thought to have originated as prokaryotic cells living symbiotically inside of primitive eukaryotic cells, this is called the [[endosymbiotic hypothesis]]</ref>.  The ends of eukaryotic chromosomes are protected by [[telomere]]s, which are always tightly condensed except during S phase of [[mitosis]].<ref>Campbell, Neil A, et. al. ''Biology''. 6th ed. San Francisco: Benjamin Cummings, 2002. 299, 530-31.</ref>

[[Prokaryotic DNA]] is circular (a closed loop).  Whereas, [[eukaryotic DNA|eukaryotic chromosomes]] are linear (with ends), with the notable exception of [[Mitochondrial DNA]] and plastid (chloroplast) DNA, which is separate from the DNA in the nucleus<ref>Mitochondria and chloroplasts are thought to have originated as prokaryotic cells living symbiotically inside of primitive eukaryotic cells, this is called the [[endosymbiotic hypothesis]]</ref>.  The ends of eukaryotic chromosomes are protected by [[telomere]]s, which are always tightly condensed except during S phase of [[mitosis]].<ref>Campbell, Neil A, et. al. ''Biology''. 6th ed. San Francisco: Benjamin Cummings, 2002. 299, 530-31.</ref>

[[Mutation]]s are simply variations in DNA sequence between individuals. The vast majority of spontaneous mutations in DNA are called "neutral" because they do not affect the [[phenotype|observable traits]] of the individual organism. Others can have beneficial effects and some can disrupt important functions  Differential distribution of one type of neutral mutations, resulting in individual to individual "restriction fragment length polymorphisms", is the basis for modern DNA fingerprinting (see below).  It is mutations in DNA, giving rise to novel alleles ("versions" of a gene), which cause phenotypic variations between individuals of a particular species.  For instance, in humans, single-gene mutations are responsible for differences in [[ABO blood type]], eye color, hair color, and even the ability to taste certain molecules.  Sadly, there are also thousands of mutations known to cause human disease; notably sickle-cell anemia, a few rare forms of autism, and (when the mutations spontaneously occur in a somatic cell) various types of cancer.  That said, it is important to note that most phenotypic traits (e.g. height) and hereditary diseases arise as the net effect of several different genetic variations.

[[Mutation]]s are simply variations in DNA sequence between individuals. The vast majority of spontaneous mutations in DNA are called "neutral" because they do not affect the [[phenotype|observable traits]] of the individual organism. Others can have beneficial effects and some can disrupt important functions  Differential distribution of various types of neutral mutations within the population is the basis for modern [[DNA fingerprinting]].  It is mutations in DNA, giving rise to novel alleles ("versions" of a gene), which cause phenotypic variations between individuals of a particular species.  For instance, in humans, single-gene mutations are responsible for differences in [[ABO blood type]], eye color, hair color, and even the ability to taste certain molecules.  Sadly, there are also thousands of mutations known to cause human disease; notably sickle-cell anemia, a few rare forms of autism, and (when the mutations spontaneously occur in a somatic cell) various types of cancer.  That said, it is important to note that most phenotypic traits (e.g. height) and hereditary diseases arise as the net effect of several different genetic variations.

[http://www.ncbi.nlm.nih.gov/omim OMIM] (Online Mendelian Inheritance in Man), is an online database of genes known to be mutated in disease states.  [[Mendelian inheritance]] refers to the inheritance pattern observed in traits that are determined by a single gene.  This pattern was first discovered by [[Gregor Mendel]], an Austrian monk, during his work with pea plants from 1856-1863.  Although Mendel published his work in 1866, it's significance was largely ignored until it was rediscovered in the early 20th century; more than two decades after his death.

[http://www.ncbi.nlm.nih.gov/omim OMIM] (Online Mendelian Inheritance in Man), is an online database of genes known to be mutated in disease states.  [[Mendelian inheritance]] refers to the inheritance pattern observed in traits that are determined by a single gene.  This pattern was first discovered by [[Gregor Mendel]], an Austrian monk, during his work with pea plants from 1856-1863.  Although Mendel published his work in 1866, it's significance was largely ignored until it was rediscovered in the early 20th century; more than two decades after his death.

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