TRANSCRIPTION FACTORS

Creationism holds that completely unrelated to other groups of organisms. Intelligent design advocates claim that life is "irreducibly complex" and that the complex molecular mechanisms of higher organisms could never have evolved through natural processes. One of the major ways in which organisms such as humans generate their complexity is through the regulation of gene expression through the use of transcription factors.

     Modern organisms are made of a variety of proteins.

FLOWER SPIDER

While modern organisms store the code for the amino acid order in proteins in their DNA, it is RNA which carries this code to the ribosomes where the proteins are actually made.  To accomplish this, sections of DNA molecules must be copied into RNA by the enzyme RNA polymerase.  This process is called transcription. 

     In eubacteria, RNA polymerase can bind to DNA and initiate transcription on its own.  In eukaryotes, the situation is much more complex and RNA cannot initiate transcription without a number of additional proteins. Archebacteria seem to require transcription factors for transcription, suggesting links between archaeal and eukaryotic mechanisms (Ouzounis, 1992).  Interestingly, archebacteria share some of these transcription factors (such as TDP and TFIIB) with eukaryotes (Bagby, 1995; Barinaga, 1994).

TRANSCRIPTION COMPLEX

Archaea use transcription factors TBP and TFB, homologs of the eukaryotic transcription factors TBP and TFIIB, for the transcription of non-stress genes.  Apparently, these are the only two transcription factors needed for RNA polymerase to bind to promoters (Thomsen, 2001).  Archaeal cells are depicted below.

 BACTERIA

 

GENE REGULATION

     In the following images of cancer cells from the breast, liver, and uterus, genes are not being regulated properly.

 CANCERCANCERCANCER

Human life would be impossible without gene regulation: liver cells must express genes that are not expressed in brain cells or white blood cells; the gene expressed during fetal development must be different from those expressed as an adult.  In the human genome, almost ¼  of the genes for proteins produce factors needed for the replication of DNA, its maintenance, and the control of gene expression.  An additional 20% of the human genome is involved in signal transduction, which includes signals which affect gene expression (Brown, p.21).  Most proteins which regulate gene expression bind to DNA and determine whether or not an RNA transcript is made from the gene. 

     Although all cells in the body possess the same genes, it is gene regulation which permits the differentiation of specialized cells. All human cells, such as those depicted in the following images (adipose, bone cells, cartilage, epithelial cells, cells of the testes, and neural tissue), have the same genes. 

adipose

spermneuron

YOUR PREDICTIONS

Evolutionary Model: If evolution is true, would you expect the thousands of transcription factor genes of the human genome to be unique structures unrelated to other genes or would you expect to find a small number of gene families which are composed of modified duplicates of ancestral genes? Would you expect other organisms, such as invertebrates, to possess homologs of the same transcription factors? Would you expect invertebrates to possess homologs of the genes whose function is required for human complexity?

Creationism Model: If creationism is true, would you expect the thousands of transcription factor genes of the human genome to be unique structures unrelated to other genes or would you expect to find a small number of gene families which are composed of modified duplicates of ancestral genes? Would you expect other organisms, such as invertebrates, to possess homologs of the same transcription factors? Would you expect invertebrates to possess homologs of the genes whose function is required for human complexity?

Intelligent Design Model: If intelligent design is true, would you expect the thousands of transcription factor genes of the human genome to be unique structures unrelated to other genes or would you expect to find a small number of gene families which are composed of modified duplicates of ancestral genes? Would you expect other organisms, such as invertebrates, to possess homologs of the same transcription factors? Would you expect invertebrates to possess homologs of the genes whose function is required for human complexity?

HOMEODOMAIN TRANSCRIPTION FACTORS
HOX CLUSTERS
HMG BOX TRANSCRIPTION FACTORS
HLH TRANSCRIPTION FACTORS
ZINC FINGER PROTEINS