The genetic blueprint of human beings consists of 23 linear chromosomes that contain 3.42 billion nucleotides. The genetic blueprints of most mammals consist of similarly significant amounts of nucleotides. Some extremes in nucleotide numbers do occur in mammals, such as the red vischaca rat (8.21 billion nucleotides) and the bent-winged bat (1.69 billion nucleotides). Regardless of what kind of animal, there is a large excess of DNA that does not code for proteins. Approximately 2% of DNA codes for proteins in humans. For several decades, scientists were confounded by the purpose of such "junk" DNA, which often consisted of repeating segments that are dispersed throughout the genome.
These repeating segments come about when sections of DNA move within the genome to different positions. This process is called transposition. Biologists now believe that these transposable segments are not useless, but instead provide greater ability for the organism to evolve. They serve as areas for genetic recombination and provide new signals for genetic expression. Genomes are dynamic, with certain elements becoming extinct as new elements appear. Functional DNA can therefore be created from "junk" DNA. The term "exaptation" is used when describing how genetic entities can change their role, despite their original role if they had one at all. For example, biologist Gill Bejarano discovered a DNA fragment that was exapted as an enhancer, increasing gene transcription, when it had originally inserted itself anywhere into the genome.
DNA sequences that are nonfunctional in certain organisms could be functional in others, becoming an exon that is transcribed to messenger RNA. While non-functional DNA can be seen as "junk" DNA they actually do actually have a role in the genome. These segments are important to evolution. To access the article that I retrieved my information from, click here.
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