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The remaining copy of the tumor suppressor gene can be inactivated by a point mutation or via other mechanisms, resulting in a loss of heterozygosity event, and leaving no tumor suppressor gene to protect the body. Loss of heterozygosity does not imply a homozygous state (which would require the presence of two identical alleles in the cell).
The wing-spot test in D. melanogaster was first described by Graf and Würgler. [3] The wing-spot test determines for the induction of mutant spots that represent the loss of heterozygozity due to point mutation, deletion, nondisjunction, or mitotic recombination using the recessive genetic markers multiple wing hair (mwh) and flare-3 (flr3), located on chromosome number 3.
SNPs can also be used to study genetic abnormalities in cancer. For example, SNP arrays can be used to study loss of heterozygosity (LOH). LOH occurs when one allele of a gene is mutated in a deleterious way and the normally-functioning allele is lost. LOH occurs commonly in oncogenesis.
Loss of heterozygosity (LOH) is a technique that can only be used to compare two samples from the same individual. LOH analysis is often used when identifying cancer-causing oncogenes in that one sample consists of (mutant) tumor DNA and the other (control) sample consists of genomic DNA from non-cancerous cells from the same individual.
In a cohort of 96 patients with pancreatic cancers, 6 cases were known to have mutation or allele loss and 11 (11.5%) patients were identified by HRDetect to an exceed cutoff of 0.7. The study observed a similar result of sensitivity approaching 100%, with five other cases identified.
In population genetics, F-statistics (also known as fixation indices) describe the statistically expected level of heterozygosity in a population; more specifically the expected degree of (usually) a reduction in heterozygosity when compared to Hardy–Weinberg expectation.
A loss in heterozygosity refers to the loss of one of two versions—or alleles—of a gene. If one of the lost alleles helps to suppress tumors, like the gene for the retinoblastoma protein for example, then the loss of heterozygosity can lead to cancer. [107]: 1236
A population bottleneck can result in a loss of heterozygosity. In this hypothetical population, an allele has become fixed after the population repeatedly dropped from 10 to 3. One of the results of population structure is a reduction in heterozygosity.