Junk DNA

Junk DNA is a term that refers to regions of DNA that are noncoding. Although these regions do not encode protein sequences, they have been found to play important roles in regulating gene expression and maintaining chromosome structure.

History

The term "junk DNA" was first used in 1972 by Susumu Ohno, a Japanese-American geneticist. Ohno proposed that while the amount of DNA in an organism (its genome size) varies greatly, the number of functional genes does not. This led him to suggest that the majority of DNA is nonfunctional, or "junk".

Function

While initially thought to be nonfunctional, research has since shown that junk DNA can have a variety of roles. These include:

• Regulation of gene expression: Some sequences in junk DNA can bind to transcription factors, proteins that control the rate of transcription of DNA to mRNA. This can influence the activity of nearby genes.

• Chromosome structure and integrity: Certain regions of junk DNA, known as telomeres and centromeres, are crucial for the proper functioning of chromosomes.

• Evolutionary innovation: Some researchers believe that junk DNA can serve as a source of new genes, a process known as gene duplication.

Controversy

The term "junk DNA" has been controversial, as it implies that these regions of the genome have no function. Many scientists now prefer terms such as "noncoding DNA" or "dark matter DNA".

See also

• Noncoding DNA
• Pseudogene
• Introns
• Exons

References

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  Diagram of a gene with introns and exons

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  Tomoko Harada

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  Francis Crick