The Creation Explanation
|Life -- Miracle, Not Accident|
Introns and Exons in the DNA of Eukaryotes
In 1977 it was discovered that in many eukaryotic organisms the coding DNA sequences of some genes exist in two or more sections called exons, which are separated by non-coding DNA sequences called introns. Therefore, the RNA transcripts contain coding RNA exons separated by non-coding introns. Consequently, RNA transcripts must be processed to become useful mRNA molecules. In the processing of an RNA transcript the non-coding RNA introns are cut out, and the coding RNA exons are spliced together to form a finished mRNA molecules which contain the codons which specify the amino acid sequence for a protein molecule. On either end of an mRNA molecule is a sequence of untranslated nucleotides the purposes of which are not fully understood. The splicing of exons to make finished mRNA molecules takes place in the cell nucleus. This amazing precision operation requires the action of more than 50 proteins and five different complex small nuclear RNAs(each composed of an RNA molecule plus protein molecules).14 The notion that such a complex system requiring so many cooperating and interdepent parts could by chance come together and be integrated into a living cell beggars the imagination.
14. Parker, Roy and Paul G. Liliciano, Nature, Vol. 361, 18 Feb. 1993, pp. 660-662.