First Marsupial Genome Indicates that Junk DNA Has Function
In the May 10th issue of Nature an international team of scientists reported a high-quality draft of the genome of the grey short-tailed opossum.
Researchers chose to focus attention on this creature because it is frequently used as a laboratory stand-in to study human diseases. Scientists are also interested in this mammal because it's a marsupial. This makes the grey short-tailed opossum genome an important reference point to help make sense of the structure and function of the human genome. (Humans are placental mammals.) As a case in point, comparisons of the human genome with vertebrate genomes have led to the discovery of several hundred novel genes and regulatory sequences.
The opossum genome contains about 20,000 genes. Remarkably, this is the same number of genes found in the human genome - and in the genomes of other placental mammals. As it turns out, nearly all of the genes in placental and marsupial genomes are the same.
Interestingly, the main difference in the genomes of these two mammal groups resides in regions of the genomes that don't code for proteins. Just over 20 percent of the noncoding sequences are unique to placental mammals. This means that the noncoding DNA harbors the genetic information responsible for the differences between marsupial and placental mammals. Presumably, these noncoding DNA sequences regulate gene expression.
Evolutionary biologists have traditionally thought of noncoding DNA as junk, the product of random biochemical events. Therefore, they consider the existence of junk DNA as one of the most potent pieces of evidence for biological evolution. According to this view, junk DNA results when undirected biochemical processes and random chemical and physical events transform a functional DNA segment into a useless molecular artifact. Junk pieces of DNA remain part of an organism's genome solely because of its attachment to functional DNA. In this way, junk DNA persists from generation to generation. Skeptics ask, "Why would a Creator purposely introduce nonfunctional junk DNA into the genomes of organisms?"
The comparative analysis of the opossum genome indicates, however, as do other studies, that junk DNA has function, leaving evolution's best argument flattened on the highway.
For a more detailed discussion of how junk DNA fits into RTB's creation model, see Who was Adam?