Junk DNA Regulates Gene Expression

My wife enjoys looking for antiques (and, to my horror, buying them.) For Amy, antiques are priceless treasures. From my standpoint, these relics from the past are just old junk.

For a number of years, biochemists thought that a vast proportion of the genomes of most organisms consisted of old “junk” DNA sequences that once had value, but were transformed into nonfunctional elements.

Evolutionary biologists 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.

Evolutionists also highlight the fact that in many instances identical (or nearly identical) segments of junk DNA appear in a wide range of related organisms. Frequently the identical junk DNA segments reside in corresponding locations in these genomes. For evolutionists, this clearly indicates that these organisms shared a common ancestor. Accordingly, the junk DNA segment arose prior to the time that the organisms diverged from their shared evolutionary ancestor. Evolutionists ask, “Why would a Creator purposely introduce nonfunctional, junk DNA at the exact location in the genomes of different, but seemingly related, organisms?”

Recent studies on junk DNA provide a response to this question, one that evolutionists find surprising, yet hard to deny. Junk DNA possesses function. (For a detailed discussion of some of these discoveries see Who Was Adam?

New work by scientists from Stanford University and the University of California, Santa Cruz on transposable elements provides added insight into the functional range of junk DNA.

Transposable elements (TE) are mobile pieces of DNA that have highly repetitive sequences. TEs duplicate themselves and then randomly insert into the genome, presumably creating junk DNA along the way.

Biochemists have noted, however, that when compared across organisms, the sequences of many TEs are nearly identical or conserved. Biochemists consider sequence conservation an indicator of function. To say it another way, TEs are not junk. If a DNA sequence is functional, any change to the sequence as a result of a mutation would potentially render it nonfunctional. In principle, lost function would compromise the fitness of the organism. And natural selection would weed it out of the population, conserving the DNA sequence.

Like my wife in an antique mall, the researchers from Stanford and UC, Santa Cruz surveyed 10,402 sequences in the human genome to gain better understanding of the function of TEs. It turns out that TEs control the activity of transcription factors. These proteins regulate gene expression. TEs also control developmental genes. These genes regulate the developmental process as organisms transform from an embryo into an adult form.

Interestingly, many of the functional TEs reside in gene deserts, vast regions in the genome devoid of genes. Based on this new research, it looks as if these genetic wastelands are replete with functional oases. In fact, one of the researchers noted that gene deserts are better described as “regulatory jungles”

The recognition that junk DNA has function weakens the best argument for biological evolution and common descent. It also explains why identical junk DNA sequences occur in corresponding regions of the genomes of related organisms. The precise location of TEs is critical for these sequences to properly regulate gene activity.

Junk DNA appears to be a valuable antique reflecting the enduring design of a Divine Craftsman, and not a trinket destined for the trash.