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In breast, ovarian, pancreatic, and prostate cancers, a core enzyme employed in homologous recombination repair (HRR) of DNA damage is often defective due to LOH, that is genetic defects in both copies (in the diploid human genome) of the gene encoding an enzyme necessary for HRR. [8]
A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosome abnormality .
The following is a list of genetic disorders and if known, type of mutation and for the chromosome involved. Although the parlance "disease-causing gene" is common, it is the occurrence of an abnormality in the parents that causes the impairment to develop within the child. There are over 6,000 known genetic disorders in humans.
An allele [1] (or allelomorph) is a variant of the sequence of nucleotides at a particular location, or locus, on a DNA molecule. [2]Alleles can differ at a single position through single nucleotide polymorphisms (SNP), [3] but they can also have insertions and deletions of up to several thousand base pairs.
Polymorphisms can be identified in the laboratory using a variety of methods. Many methods employ PCR to amplify the sequence of a gene. Once amplified, polymorphisms and mutations in the sequence can be detected by DNA sequencing, either directly or after screening for variation with a method such as single strand conformation polymorphism analysis.
ILS occurs in the context of a gene in an ancestral species which exists in multiple alleles. If a speciation event occurs in this situation, either complete lineage sorting will occur, and both daughter species will inherit all alleles of the gene in question, or incomplete lineage sorting will occur, when one or both daughter species inherits ...
In Mendelian inheritance, genes have only two alleles, such as a and A. Mendel consciously chose pairs of genetic traits, represented by two alleles for his inheritance experiments. In nature, such genes often exist in several different forms and are therefore said to have multiple alleles. An individual usually has only two copies of each gene ...
When a DNA trinucleotide repeat sequence is damaged, it may be repaired by processes such as homologous recombination, non-homologous end joining, mismatch repair or base excision repair. Each of these processes involves a DNA synthesis step in which strand slippage might occur leading to trinucleotide repeat expansion. [4]