30 years ago: Mutation driven evolution - Today: Clever and complex mechanisms such as RNA editing
Modern science has revealed several incredible mechanisms behind cellular differentiation and organismal adaptation. One of the most sophisticated mechanisms by which the cell is able to increase the number of different proteins without the need to increase the number of genes (DNA) in the genome, is RNA editing. Together with alternative splicing, these two mechanisms make it possible for the cell to produce a huge number of different proteins without modifying the underlying DNA. But 20-30 years ago these mechanisms were not well understood in scientific research and this is why many people are indoctrinated with a pseudoscientific mantra: 'mutation driven evolution'. However, newest research has found out many complex mechanisms that require Intelligent Design. Let's have an example: Apolipoprotein B-100.
Humans have a single locus encoding the APOB gene.
- It contains 29 exons (separated by 28 introns).
- The exons contain a total of 4564 codons.
- Codon 2153 is CAA, which is a codon for the amino acid glutamine (Gln).
- The gene is expressed in cells of both the liver and the intestine.
- In both locations, transcription produces a pre-messenger RNA that must be spliced to produce the mRNA to be translated into protein.
- In the Liver. Here the process occurs normally producing apolipoprotein B-100 — a protein containing 4,563 amino acids — that is essential for the transport of cholesterol and other lipids in the blood.
- In the Intestine
- In the cells of the intestine, an additional step of pre-mRNA processing occurs: the chemical modification of the C nucleotide in Codon 2153 (CAA) into a U.
- This RNA editing changes the codon from one encoding the amino acid glutamine (Gln) to a STOP codon (UAA)
- The modification is catalyzed by the enzyme cytidine deaminase that
- recognizes the sequence of the RNA at that one place in the molecule and
- catalyzes the deamination of C thus forming U.
- Translation of the mRNA stops at codon #2153 forming apolipoprotein B-48 — a protein containing 2152 amino acids — that aids in the absorption of dietary lipids from the contents of the intestine.
My comment: This clever modification was done by a cytidine deaminase that converts a C in the RNA to uracil (U). Another, even more sophisticated substitutional RNA editing mechanism is A-to-I RNA editing. This is a masquearading technique; a mechanism that converts adenosine residues to inosine residues (which masquerade as guanosine residues) in messenger RNA. The cell is also able to insert/delete/repair nucleotides in the RNA (mediated by guide RNAs). Both alternative splicing and RNA editing mechanisms are controlled by epigenetic mechanisms and factors. They help us understand that rich biodiversity is based on clever mechanisms, not random mutations and selection. We can observe change in created kinds which is not evolution. Don't get lost, my friends.
