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Gene duplications can arise as products of several types of errors in DNA replication and repair machinery as well as through fortuitous capture by selfish genetic elements. Common sources of gene duplications include ectopic recombination , retrotransposition event, aneuploidy , polyploidy , and replication slippage .
The study of human genetic variation has evolutionary significance and medical applications. It can help scientists reconstruct and understand patterns of past human migration. In medicine, study of human genetic variation may be important because some disease-causing alleles occur more often in certain population groups.
Duplications can occur within a lineage (e.g., humans might have two copies of a gene that is found only once in chimpanzees) or they are the result of speciation. For example, a single gene in the ancestor of humans and chimpanzees now occurs in both species and can be thought of as having been 'duplicated' via speciation.
Evolution by gene duplication is an event by which a gene or part of a gene can have two identical copies that can not be distinguished from each other. This phenomenon is understood to be an important source of novelty in evolution, providing for an expanded repertoire of molecular activities.
[24] [25] Tools such as multiplex ligation-dependent probe amplification can also be used to look for duplications or deletions of genes or gene sections. [25] Other techniques are meant to assess a large number of SNPs across the genome, such as SNP arrays. [24] [25] This type of technology is commonly used for genome-wide association studies.
The alignable sequences within genomes of humans and chimpanzees differ by about 35 million single-nucleotide substitutions. Additionally about 3% of the complete genomes differ by deletions, insertions and duplications. [16] Since mutation rate is relatively constant, roughly one half of these changes occurred in the human lineage.
An inversion occurs when a chromosome undergoes a two breaks within the chromosomal arm, and the segment between the two breaks inserts itself in the opposite direction in the same chromosome arm. The breakpoints of inversions often happen in regions of repetitive nucleotides, and the regions may be reused in other inversions. [ 1 ]
Twin studies provide a unique opportunity to explore the genetic and environmental influences on autism spectrum disorder (ASD). By studying identical twins, who share identical DNA, and fraternal twins, who share about half of their DNA, researchers can estimate the heritability of autism by comparing the rates of when one twin is diagnosed with autism while the other is not in identical vs ...