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Cancer Biology and Genetics for Non-Biologists
Published in Trevor F. Cox, Medical Statistics for Cancer Studies, 2022
A gene can have different codings, and these variants are called alleles. One allele is inherited from your mother and one from your father for each gene, and these determine your physical traits (phenotype), such as hair colour, height, etc. The combination of the alleles that you have inherited make up your genotype, but we can also use this term for a particular gene. If there are two possible alleles for a gene, A and a, there are three possible genotypes, AA, Aa and aa, depending on which alleles you inherited. For example, the OCA2 gene on chromosome 15 is associated with melanin production, which is a pigment for hair, eye and skin colour. A might be the allele for brown eyes and a for blue eyes. A is dominant and a is recessive, and so individuals with AA and Aa will have brown eyes, and individuals with aa will have blue eyes. But eye colour is not quite so simple as this as other genes are also involved. The allele that codes for the most common phenotype is called the wild type allele.
Basic genetics and patterns of inheritance
Published in Hung N. Winn, Frank A. Chervenak, Roberto Romero, Clinical Maternal-Fetal Medicine Online, 2021
There are four basic inheritance patterns of human single-gene disorders. These include autosomal dominant and autosomal recessive inheritance, in which the mutant gene is on an autosome, and X-linked dominant and X-linked recessive inheritance, in which the mutant gene is on the X chromosome. Individuals can be heterozygous for a given gene, meaning that they have two different forms, or alleles, of the gene at the same locus on each of the two different chromosomes. Individuals can also be homozygous for a gene, in which the two alleles are identical. Males are said to be hemizygous with respect to genes on the X chromosome, since they have only one copy of the X.
Serological Typing of HLA-A, -B, and -C Antigens
Published in M. Kam, Jeffrey L. Bidwell, Handbook of HLA TYPING TECHNIQUES, 2020
Oligonucleotide typing for class I antigens is still under development, but major advances are expected within the next few years. Alleles can only be tested for if the DNA sequence is known so that appropriate primers and probes can be made. The major obstacle is the selection of primers which will amplify allele-specific sequences and the generation of probes that do not cross-hybridize with alleles of the same group. Allelic differences may be only a few amino acids as for B702 and B703 or the amino acid differences may be at various positions along the αl, α2, and β pleated sheet.
Geolocation prediction from STR genotyping: a pilot study in five geographically distinct global populations
Published in Annals of Human Biology, 2023
Mansi Arora, Hirak Ranjan Dash
However, many STR markers generated a common “most frequent genotype,” irrespective of the populations tested. This does not add any additional information to distinguish between the tested populations. Hence the second most frequent genotypes were assessed to reach a sufficient level of discrimination. When the second most frequent genotype was considered, D1S1656, D2S1338, and D7S820 emerged as the most discriminatory markers (Table 4). In these markers, though some of the populations shared the most-frequent genotype, the second most frequent genotype differed from one population to another. In forensic population genetics studies, the most common alleles are analysed for the STR markers tested (Projić et al. 2007). However, as forensic DNA analysis envisions distinguishing between two individuals, the commonly occurring alleles with low discrimination power are considered least useful (Schneider 2012). On the contrary, considering the population-specific most frequent alleles is highly useful in generating investigative leads such as attributing the biogeographical location of an individual (Battey et al. 2020).
The role of CYP2C19 genotyping to guide antiplatelet therapy following ischemic stroke or transient ischemic attack
Published in Expert Review of Clinical Pharmacology, 2022
John H McDermott, Marc Leach, Dwaipayan Sen, Craig J. Smith, William G. Newman, Philip M. Bath
The proper functioning of pharmacokinetic proteins, such as ABCB1 and CYP2C19, is associated with variation in their genetic sequence. Many of these genes are highly polymorphic, meaning there are many sequence variants which can occupy the same genomic position (alleles) within a given population. Much of this variation will have very little impact on protein function, but some genetic variation can disrupt the activity of the protein product. In some cases, just one sequence variant in a gene related to drug metabolism is capable of rendering the medicine ineffective [28]. These pharmacogenetic variants are common in the general healthy population and can contribute significantly to differences observed in drug efficacy and can markedly increase the risk of adverse drug reactions (ADRs).
Evaluation of diallelic STR markers with inter-population allelic database for their usefulness in paternity trios in the Central Indian population
Published in Annals of Human Biology, 2021
Hirak Ranjan Dash, Kamayani Vajpayee, Radhika Agarwal, Anubha Gang, Ritesh Shukla, Ankit Srivastava
The genome of an offspring contains two alleles from each parent, assigned as obligate alleles. The finding of such alleles straightforwardly determines the father-child relationship when the mother is considered to be known in a case of paternity dispute (Grover et al. 2017). Two obligate alleles appear in instances when both the mother and child possess the consistent heterozygous genotype. Such occasions were observed rarely in an average of 16.08 instances in 100 paternity dispute cases tested in this study, where highest incidences were observed at D19S433 (32 occasions) and the lowest at SE33 (3 occasions). The number of instances of one or two obligate alleles was compared with forensic and paternity parameters (Dixit et al. 2019) for their possible correlation. A statistically significant positive correlation (p < 0.005) was observed between the occurrence of one obligate allele in STR markers with Power of Discrimination (PD), Polymorphic Information Content (PIC), Power of Exclusion (PE), Paternity Index (PI), and Observed and Expected Heterozygosity (Ho and He), whereas a statistically significant negative correlation (p < 0.005) was observed with Matching Probability (Pm) (Table 2). This strongly suggests the influence of the aforementioned forensic and paternity parameters on the observance of only one obligate allele in disputed paternity cases in the central Indian population.