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Allele. An allele[1], or allelomorph, is a variant of the sequence of nucleotides at a particular location, or locus, on a DNA molecule. [2] Alleles can differ at a single position through single nucleotide polymorphisms (SNP), [3] but they can also have insertions and deletions of up to several thousand base pairs. [4]
Allele frequency spectrum. In population genetics, the allele frequency spectrum, sometimes called the site frequency spectrum, is the distribution of the allele frequencies of a given set of loci (often SNPs) in a population or sample. [1][2][3][4] Because an allele frequency spectrum is often a summary of or compared to sequenced samples of ...
When multiple different alleles for a gene are present in a species's population it is called polymorphic. Most different alleles are functionally equivalent, however some alleles can give rise to different phenotypic traits. A gene's most common allele is called the wild type, and rare alleles are called mutants.
Thus you can tell that each allele is present in the heterozygote. [9] Codominance refers to the allelic relationship that occurs when two alleles are both expressed in the heterozygote, and both phenotypes are seen simultaneously. [10] Multiple alleles refers to the situation when there are more than 2 common alleles of a particular gene.
However speciation has been observed in present-day organisms, and past speciation events are recorded in fossils. [73] [74] [75] Scientists have documented the formation of five new species of cichlid fishes from a single common ancestor that was isolated fewer than 5,000 years ago from the parent stock in Lake Nagubago. [76]
A mode of speciation where the evolution of reproductive isolation is caused by the geographic separation of two or more populations of a single species. [5] allopatric taxa Specific species that are allopatrically distributed. allopatry The phenomenon by which two or more populations of a single species exist in geographic isolation from one ...
The genotype of an organism is its complete set of genetic material. [1] Genotype can also be used to refer to the alleles or variants an individual carries in a particular gene or genetic location. [2] The number of alleles an individual can have in a specific gene depends on the number of copies of each chromosome found in that species, also ...
Cave paintings (such as this one from France) represent a benchmark in the evolutionary history of human cognition. Victorian naturalist Charles Darwin was the first to propose the out-of-Africa hypothesis for the peopling of the world, [39] but the story of prehistoric human migration is now understood to be much more complex thanks to twenty-first-century advances in genomic sequencing.