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How do single nucleotide polymorphisms differ from larger DNA insertions and deletions?
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human genome
The human genome is made up of approximately three billion base pairs of deoxyribonucleic acid (DNA). The bases of DNA are adenine (A), thymine (T), guanine (G), and cytosine (C).
In the study of the human genome, single nucleotide polymorphisms (SNPs) and insertions/deletions (indels) represent distinct types of genetic markers.
The primary differences between them include:
- Nature of Variation: SNPs involve a change to a single nucleotide building block—adenine, guanine, thymine, or cytosine—within a DNA segment. For example, a sequence might show a C in one individual and a G in another at the same position.12
- Structural Change: Indels are characterized by the presence or absence of a piece of DNA sequence. In this type of polymorphism, a specific segment of the sequence exists in some individuals (the insertion allele) but is entirely missing in others (the deletion allele).1
While both serve as important tools for genetic mapping and identifying genes associated with disease, SNPs are the most common form of genetic variation in humans, accounting for roughly 90 percent of the genetic differences between individuals.12