This is a podcast from Cold Spring Harbor [Dark Matter of the Genome, Pt. 1 (Base Pairs Episode 8)]. The authors try to convince us that most of the genome is mysterious "dark matter," not junk. The main theme is that the genome contains transposons that could play an important role in evolution and disease.
Here's a few facts.
- A gene is a DNA sequence that's transcribed. There are about 20,000 protein-coding genes and they cover about 25% of the genome (including introns). It's false to say that genes only occupy 2% of the genome. In addition to protein-coding genes, there are about 5,000 noncoding genes that take up about 5% of the genome. Most of them have been known for decades.
- It has been known for many decades that the human genome has no more than 30,000 genes. This fact was known by knowledgeable scientists long before the human genome sequence was published.
- It has been known for decades that about 50% of our genome is composed of defective bits and pieces of once-active transposons. Thus, most of our genome looks like junk and behaves like junk. It is not some mysterious "dark matter." (The podcast actually say that 50% of our genome is defective transposons but they claim this is a recent discovery and it's not junk.)
- The evidence for junk DNA comes from many different sources. It's not a mystery. It's really junk DNA. The term "junk DNA" was not created to disguise our ignorance of what's in your genome.
- In addition to genes, there are lots of other functional regions of the genome. No knowledgeable scientists ever thought that the only functional parts of the genome were the exons of protein-coding genes.
Most of the genome is not genes, but another form of genetic information that has come to be known as the genome’s “dark matter.” In this episode, we explore how studying this unfamiliar territory could help scientists understand diseases such as ALS.
