Photo by Patrizia Ferri

The domestic onion, Allium cepa, is a diploid plant (2n = 16) with a haploid genome size of roughly 16 billion base pairs (16 Gbp), or about five times larger than humans. … why does an onion require five times more DNA than a human? (Photo by Patrizia Ferri)

Dr. Palazzo, in collaboration with Dr. T. Ryan Gregory from the University of Guelph, published a perspective titled “The Case for Junk DNA” that appeared in the May 2014 issue of PLOS Genetics. It was highlighted on the National Geographic website.

Overview of the Paper:

With the advent of deep sequencing technologies and the ability to analyze whole genome sequences and transcriptomes, there has been a growing interest in exploring putative functions of the very large fraction of the genome that is commonly referred to as “junk DNA.” Whereas this is an issue of considerable importance in genome biology, there is an unfortunate tendency for researchers and science writers to proclaim the demise of junk DNA on a regular basis without properly addressing some of the fundamental issues that first led to the rise of the concept. In this review, we provide an overview of the major arguments that have been presented in support of the notion that a large portion of most eukaryotic genomes lacks an organism-level function. Some of these are based on observations or basic genetic principles that are decades old, whereas others stem from new knowledge regarding molecular processes such as transcription and gene regulation.


Summary of haploid nuclear DNA contents (“genome sizes”) for various groups of eukaryotes in megabase pairs.
This graph is based on data for about 10,000 species [18], [19]. There is a wide range in genome sizes even among developmentally similar species, and there is no correspondence between genome size and general organism complexity. Humans, which have an average-sized genome for a mammal, are indicated by a star. Note the logarithmic scale.

Read the whole paper on PLOS Genetics.