Biochemistry

"Junk" DNA as Evidence for Evolution?

January, 2003

"It is a capital mistake to theorize before you have all the evidence. It biases the judgment."-Sherlock Holmes in a Study of Scarlet

Back in the 1960s, scientists discovered sections of DNA that did not code for proteins. These non-coding DNA strands were assumed to be non-functional and were referred to as "junk" DNA, the presumed evolutionary remnants of ancestral organisms. 1 Almost 99% of human DNA is known to be non-coding.

A little background will facilitate discussion of non-coding DNA. Information in coding DNA sequences is transcribed into mRNA (Figure 1). mRNA exits the nucleus and attaches to ribosomes, the molecular machines that generate proteins. In the ribosome, the information in the mRNA is translated into an amino acid sequence to form a protein.

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Figure 1: Protein Formation from Coding DNA

The transcription of information from DNA to mRNA is where non-coding DNA is encountered (Figure 2).

Evolution’s False Start: The Spontaneous Generation of Life

April, 2018

The date was August 28, 2011. The setting was the biennial world-championship of track and field, held on this occasion in Daegu, South Korea. The “world’s fastest man,” Jamaica’s Usain Bolt was expected to easily defend his 100-meter crown that he won in 2009 after also taking the Olympic gold in 2008. Two of his main competitors were not even in the race. Jamaican teammate Asafa Powell withdrew right before the event with a groin injury and American rival Tyson Gay was out of commission with a hip injury. Bolt had cruised through the preliminary heats, and it seemed like a gold medal was a forgone conclusion, but something very unexpected happened. After getting set in the starting block, Bolt jumped the gun! He was disqualified by the very controversial new “zero-tolerance” false start rule that had been enacted the previous year. Under the new rule, there were no second chances! A single false start now disqualified a runner. Therefore, there was now no chance that Bolt would repeat as world champion in the 100 meters because everyone knows that you can’t win the race if you aren’t able to start the race! Similarly, you can’t win the race if you can’t “get out of the blocks” (due to injury, cramping, or whatever). Either way, whether as a result of inability or disqualification, the failure to get started down the track makes it impossible to even finish the race, much less win the race! On this occasion it mattered not that Bolt was the world’s fastest man because there was now a 0% probability that he would win the race.

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