The Proceedings of the Eighth International Conference on Creationism (2018)

Mechanism Action Reference Research Entity Results Descriptive Extract of Function in CET Framework 1. Regulated Tandem Repeat Sequence Number Gradual changes in the repeated num- ber of short DNA sequences, dubbed “units,” arranged in head-to-tail (TR) sequences found within a promoter which yield gradual variations in gene expression. Fondon and Gar- ner. 2004. Molecu- lar origins of rapid and continuous morphological evo- lution. PNAS Comparative ge- nomic study of re- petitive elements in developmental genes in 92 breeds of dogs. TR expansion and contraction contributes to incremental control of: transcription, mRNA process- ing, protein translation, folding, stability, aggregation rates, and gross morphology. Variations in the number of repeats in the coding regions of the Alx-4 and Runx-2 were quantitatively associated with significant differences in limb and skull morphology. “The high frequency and incre- mental effects of repeat length mutations provide molecular explanations for swift, yet topolog- ically conservative morphological evolution...revealing evidence sup- porting an alternative hypothesis that length variations in tandemly repeated sequences are a major source of morphological variation... that permit rapid generation of useful alleles...abundant in the coding sequences of vertebrate genes, especially those involved in development...repeat expansions or contractions vary in a locus-spe- cific manner and occur at rates up to 100,000 times higher than point mutations...how broadly this mode of evolutionary change is exploited in nature remains to be seen, but if the prevalence of repetitive ele- ments within genes is any indicator, then mammals, insects, plants, and other genomes throughout the nat- ural world may use this mechanism to achieve evolutionary agility" pgs. 18058, 18062. Gemayel, et al. 2010. Variable Tan- dem Repeats Ac- celerate Evolution of Coding and Reg- ulatory Sequences. Annual Review of Genetics Review article Properties or functions influenced by tandem repeats: overlap with regulatory protein binding sites, chromatin structure, Z-DNA forma- tion, spacing of promoter elements, RNA structure. “That these sequences are rapidly changing among primates suggests that this mutational hot spot may also be driving rapid evolution of MMP3 gene expression and its associated phenotypes....tandem repeats provide a simple, monogen- ic mechanism that allows tuning of gene expression or function. The role of variable tandem repeats in mediating variable gene expres- sion for quantitative phenotypic changes…whereas tandem repeat variation is by definition a genetic change, it also shares certain char- acteristics with epigenetic changes (e.g., the high instability and com- plete reversibility)" p. 468, 470. Guliuzza and Gaskill ◀ How organisms continuously track environmental changes ▶ 2018 ICC 174 Table 2. Multiple regulated mechanisms identified to produce rapid phenotypic variation. Variations are often predictable and a targeted solution to a specifically detected environmental challenge. The role a mechanism serves to enable an organism to continuously track environmental conditions is supported by an extraction from the reference article. Table 2 continued on next page.