Evolution of Genes - Natural Selection, Point Mutations In Existing Genes, Alleles, Gene Duplication, Gene Families, Pseudogenes
earlier fossil creatures understand
Individual genes and whole genomes change over time. Indeed, evolution of genes ultimately accounts for the evolution of organisms that is seen in the fossil record: Humans evolved from earlier apes, and those creatures from their ancestors, by gene changes in the earlier creatures. Just as the fossil record can be examined to understand the patterns of organismic evolution, so too can genes be compared to understand genomic evolution.
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Most changes that occur in genes are subject to natural selection, the process first outlined by Charles Darwin in 1859. In natural selection, a heritable change arises by chance. If the organism with that change is better able to survive and reproduce, it will leave more descendants in future generations. These descendants will also carry the new genetic change, and as they reproduce, the change …
Genes are long strings of four nucleotides (abbreviated A, T, C, and G) whose order dictates the order of amino acids in proteins (or nucleotides in RNA). A point mutation is a change in a single nucleotide position at a
Mutations in the coding region may change the protein that results. Mutations in the promoter can affect how transcription factors bind, altering the level of gene expression.…
Occasionally a gene on a single chromosome will be duplicated to create a pair of identical genes. Duplication may occur for any one of several reasons. One type of duplication occurs when the RNA transcript of a gene is "reverse transcribed" back into a DNA sequence and reinserted elsewhere in the genome (a process called retroposition), leading to a new, possibly functional copy of…
Transposable genetic elements are DNA segments that move around in the genome. Many biologists consider them to be a form of "selfish DNA," a kind of genetic parasite that serves no useful function for the host, but remains in the genome because it is efficient at getting itself copied. They can be present in large numbers of copies. In humans, more than a million copies of a single …
The coding portions of eukaryotic genes, termed "exons," are interrupted by noncoding regions, termed "introns." The evolutionary role of introns has been controversial since their discovery in 1977. Some scientists propose they are just another form of "junk DNA," and may be the relics of transposable elements or other forms of selfish DNA. Others suggest…
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