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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 .
A further 12% of cases are predicted to be caused by protein altering missense mutations that change an amino acid but do not inactivate a gene. [29] Therefore, approximately 30% of individuals with autism have a spontaneous de novo large CNV that deletes or duplicates genes, or mutation that changes the amino acid code of an individual gene.
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.
The mode of duplication by which redundancy occurs has been found to impact the classifications in breast cancer disposition genes. [19] Gross duplications complicate clinical interpretation because it is difficult to discern if they occur in tandem. Recent methods, like DNA breakpoint assay, have been used to determine tandem status. [19]
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.
Genomic structural variation is the variation in structure of an organism's chromosome, such as deletions, duplications, copy-number variants, insertions, inversions and translocations. Originally, a structure variation affects a sequence length about 1kb to 3Mb, which is larger than SNPs and smaller than chromosome abnormality (though the ...
[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.
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 ]