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An inversion is a chromosome rearrangement in which a segment of a chromosome becomes inverted within its original position. 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 classical example is the Drosophila w m4 (speak white-mottled-4) translocation. In this mutation , an inversion on the X chromosome placed the white gene next to pericentric heterochromatin, or a sequence of repeats that becomes heterochromatic. [ 3 ]
Biased gene conversion (BGC) occurs when one allele has a higher probability of being the donor than the other in a gene conversion event. For example, when a T:G mismatch occurs, it would be more or less likely to be corrected to a C:G pair than a T:A pair. This gives that allele a higher probability of transmission to the next generation.
The products of this mechanism from the sequence repeats is depicted in Figure 2. A study was done on the olfactory receptor gene clusters where they questioned if there was an association between normal rearrangement of 8p and the repeated inverted sequences. The researchers observed that the rearrangement of chromosomes was actually caused 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]
All gene segments between the V β-D β-J β gene segments in the newly formed complex are deleted and the primary transcript is synthesized that incorporates the constant domain gene (V β-D β-J β-C β). mRNA transcription splices out any intervening sequence and allows translation of the full length protein for the TCR β-chain.
The HD gene [8] is found in all human genomes. In the event that a slippage event occurs there can be a large expansion in the tandem repeats of the HD gene. [8] An individual who is not affected by Huntington's disease will have 6-35 tandem repeats at the HD locus. However, an affected individual will have 36- 121 repeats present. [7]
This opens up the usually tightly packed nucleosome and allows transcription machinery to come into contact with the DNA template, leading to gene transcription. [1]: 242 Repression of gene transcription is achieved by the reverse of this mechanism. The acetyl group is removed by one of the HDAC enzymes during deacetylation, allowing histones ...