Atlanta -- Emory University scientists have identified and created a map of more than 400,000 insertions and deletions (INDELs) in the human genome that signal a little-explored type of genetic difference among individuals. INDELS are an alternative form of natural genetic variation that differs from the much-studied single nucleotide polymorphisms (SNPs). Both types of variation are likely to have a major impact on humans, including their health and susceptibility to disease.
The INDEL research, led by Scott Devine, PhD, assistant professor of biochemistry at Emory University School of Medicine, has been posted online and will be published in the September issue of the journal Genome Research.
The human genome sequence in our DNA contains three billion base pairs of four chemical building blocks adenine, thymine, cytosine, and guanine (A, T, C, G), strung together in different combinations in long chains within 23 pairs of chromosomes. When the first human genome was being sequenced, it became apparent that additional human genomes would have to be sequenced to identify the places in the genetic code that account for human variation. Scientists now know that humans share about 97-99 percent of the genetic code, and the remaining 1-3 percent dictates individual differences. These naturally occurring differences, called polymorphisms, help explain differences in appearance, susceptibility to diseases, and responses to the environment.
SNPs are differences in single chemical bases in the genome sequence, and INDELs result from the insertion and deletion of small pieces of DNA of varying sizes and types. If the human genome is viewed as a genetic instruction book, then SNPs are analogous to single letter changes in the book, whereas INDELs are equivalent to inserting and deleting words or paragraphs.
Most polymorphism discovery projects have focused on SNPs, resulting in the International HapMap Project a catalog and map
Contact: Holly Korschun
Emory University Health Sciences Center