Practise AP Biology 7.10.C questions by explaining how geographic isolation and reproductive barriers reduce gene flow and drive speciation.
Researchers study mechanisms that enable or prevent speciation.
Describe a post-zygotic mechanism that prevents gene flow and thus enables speciation.
New genes can evolve from noncoding regions of DNA. It is not until certain regulatory elements are present in the DNA that a noncoding region becomes a new, functional gene that encodes a protein. These regulatory elements include a promoter, a 5' untranslated region (UTR) followed by a start codon, and a 3' UTR following a codon (Figure 1).
Figure 1. Basic structure of a functional ag gene
Researchers studied the evolution of the family of antifreeze-glycoprotein (AG) encoding genes in Gadidae, a family of marine fish known as cods. When present in the fish, these glycoproteins reduce the freezing temperature of the fish. The researchers compared genomic sequences in nine cod species and one non-cod fish species, B. brosme. They recorded the presence or absence of the elements of functional ag genes as well as ag-like sequences that are similar to a functional gene but have undergone mutation and do not contain all the elements required to enable protein production (Figure 2).
Figure 2. Phylogenetic tree showing the evolution of a g genes