Human Genome Variation

TABLE 19.5 Human Genome Variations Type Allelic variation Single nucleotide polymorphisms (SNPs) Copy number variations (CNVs) Variable number tandem repeats (VNTRs) Epigenetic markers Description The number of alleles of a given gene, or the sum of allelic differences between individuals or populations. Single base changes that occur about every 1,000 nucleotides. There may be 10—12 million SNPs in the genome, only about 1% of which have functional significance. Short (>1,000 base pairs) deletions, insertions, inversions, and duplications of genomic regions. About 0.4% of the genomes of unrelated people differ in CNVs. Short nucleotide sequences organized as tandem repeats, showing variation in repeat length between individuals. There are two groups of VNTRs: minisatellites (15—100 base pairs) and microsatellites (5—1 5 base pairs). Both are used in personal identification. Epigenetic markers are modifications in DNA that do not change the nucleotide sequence. These changes alter gene expression. Most epigenetic markers are erased and remarked each generation, but some markers are passed to the next generation. © Cengage Learning