Allele distribution/ frequencies differences

Population subsamples of American and African blacks, however, show a significantly different bell-shaped Lp(a) distribution (H6, P5, S40) (Fig. 7). The mean levels are twice those in Caucasians, indicating that the Lp(a) distribution depends upon race (G37). As there is an inverse relation between apo(a) size and plasma concentration, the distribution of different genotypes and allele frequencies is also dependent upon race (C6, Ml3). 

Importantly, different populations tend to have different frequency distributions of alleles and exhibit different patterns of hnkage disequilibrium. This variability exists among both racial and ethnic groups. 

Rapid, accurate SNP validation can be carried out using a sample-pooling technique—allele frequency—that rapidly screens and confirms the presence of an SNP and its allelic frequency in patient populations. Conventional technologies typically analyze each SNP in each individual of the population in question, and individual results are then consolidated to yield the overall SNP allele-frequency distribution. MS-based technology is able to determine SNP allele frequencies with high precision in pooled samples, thereby replacing hundreds of individual measurements with one consolidated analysis. To that end, DNA is isolated, purified, and quantitated. A pool of DNA is formed from a high number of different individuals, amplified, and mass measured. 

The distribution of ACE genotypes in the Spanish population was as follows ACE-I/I 14.8% in controls and 20.5% in AD ACE-I/D 45.6% in controls and 46.0% in AD and ACE-D/D 39.6% in controls and 33.5% in AD (623). In this study, a small increase in the frequency of ACE- allele was observed in LOAD (623). Nevertheless, as with many other polymorphic genes, some authors did not find association between the ACE-I/D polymorphism and AD in different populations (80,617,624-631). However, a meta-analysis of 12 case-control series published up to the year 2000 suggested that ACi genotypes are associated with AD (611), and that the ACE-D allele is more frequent in Spanish, American, and Russian AD patients than in controls (614,615,617) but not in the Italian and Jewish populations (627,632). 

De Olano, M., Fernandez-Novoa, L., Mesa, M.D., Corzo, L., Cacabelos, R. (2000) Different allelic frequency distribution in angiotensin-converting enzyme I/D polymorphism and angi-otensinogen M235T polymorphism in dementia. In Sixth International Stockholm/ Springfield Symposium Advanced Alzheimer Therapy, Stockholm, p. 202. 

Enzyme levels and activities within the human population can vary considerably and many of the enzymes involved in the metabolism of xenobiotics are polymorphicaUy distributed in the human population. Genetic polymorphism (from Greek poly many , morph form ) is defined as the occurrence of at least two different alleles, with allele frequencies exceeding 1% at a particular locus. The allelic variants include point mutations as well as deletions and insertions and genetic polymorphism may cause an increase, a decrease, or no change in enzymatic activity. 

The importance of STR analysis stems from the observation that while some STRs are constant in their repeat number across entire populations, others are highly variable in repeat number. This variability has been shown in all species looked at. It has also been shown that not all the different alleles occur at the same frequency in any given species. So for a specified STR some alleles will be commoner than others, the distribution frequently approximating to normal, with very small and very large repeat numbers being rarest. Because this is not always the case we can surmise that. some other mechanism than simple random processes are affecting repeat numbers of STRs. 

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