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G-banding patterns of human chromosome 3 in three different resolutions (400, [14] 550 [15] and 850 [3]). Band length in this diagram is based on the ideograms from ISCN (2013). [ 16 ] This type of ideogram represents actual relative band length observed under a microscope at the different moments during the mitotic process .
Chromosomal reciprocal translocation of the 4th and 20th chromosome. In genetics, chromosome translocation is a phenomenon that results in unusual rearrangement of chromosomes. This includes balanced and unbalanced translocation, with two main types: reciprocal, and Robertsonian translocation.
Gene conversion is the process by which one DNA sequence replaces a homologous sequence such that the sequences become identical after the conversion. [1] Gene conversion can be either allelic, meaning that one allele of the same gene replaces another allele, or ectopic, meaning that one paralogous DNA sequence converts another.
3 = chromosome 3; p = p-arm; 22 = region 2, band 2 (read as "two, two", not "twenty-two") 1 = sub-band 1; Thus the entire locus of the example above would be read as "three P two two point one". The cytogenetic bands are areas of the chromosome either rich in actively-transcribed DNA (euchromatin) or packaged DNA (heterochromatin).
One of the sequences is thus lost and replaced with the duplication of another sequence. When two sequences are misaligned, unequal crossing over may create a tandem repeat on one chromosome and a deletion on the other. The rate of unequal crossing over will increase with the number of repeated sequences around the duplication.
Site-specific recombination, also known as conservative site-specific recombination, is a type of genetic recombination in which DNA strand exchange takes place between segments possessing at least a certain degree of sequence homology. [1] [2] [3] Enzymes known as site-specific recombinases (SSRs) perform rearrangements of DNA segments by ...
The first fusion gene [1] was described in cancer cells in the early 1980s. The finding was based on the discovery in 1960 by Peter Nowell and David Hungerford in Philadelphia of a small abnormal marker chromosome in patients with chronic myeloid leukemia—the first consistent chromosome abnormality detected in a human malignancy, later designated the Philadelphia chromosome. [3]
DNA transposons are DNA sequences, sometimes referred to "jumping genes", that can move and integrate to different locations within the genome. [1] They are class II transposable elements (TEs) that move through a DNA intermediate, as opposed to class I TEs, retrotransposons , that move through an RNA intermediate. [ 2 ]