The human genome is over 99.9% identical between individuals, yet genetic differences exist at millions of bases. The human genome contains approximately 3 million variant positions per individual, many of which are heterozygous, contributing to genetic diversity and individual traits. Genetic variations include single-nucleotide polymorphisms (SNPs), insertions, deletions, and copy number variations (CNVs).
SNPs, the most common variation, involve single-base changes in DNA. These can be synonymous, which does not alter protein sequences, or nonsynonymous, which can affect protein function. Some SNPs in non-coding regions regulate gene expression, influencing drug responses. Haplotypes, which are groups of linked SNPs, provide deeper insights into disease genetics.
Insertions and deletions (indels) involve the addition or removal of DNA segments. CNVs are larger changes that include gene duplications, leading to increased protein expression or gene deletions, resulting in complete loss of function. These variations contribute to differences in drug metabolism and efficacy.
Phenotypic traits, such as poor metabolizer status, arise from inherited nonfunctional alleles. Some traits are autosomal recessive, requiring two defective alleles, while others show codominance or incomplete dominance, where heterozygotes display combined or intermediate phenotypes. Drug response variability is often influenced by multiple genes rather than single-gene variations.
Mutations may be classified by their effects, including point mutations such as missense, nonsense, and frameshift mutations, which can alter protein function. Loss-of-function mutations reduce protein activity, while gain-of-function mutations enhance or modify protein behavior. Regulatory mutations in non-coding regions can affect gene expression and disease susceptibility. Examples include mutations in the FMR1 gene (fragile X syndrome) and genes associated with osteoporosis and diabetes.
Pharmacogenomics focuses on how genetic variations affect drug metabolism. Metabolism modifies drugs through Phase I (functionalization) and Phase II (conjugation) reactions, generally increasing water solubility for excretion. Polymorphisms in drug-metabolizing enzymes, such as CYP2D6, CYP2C9, and DPD, impact drug efficacy and toxicity, influencing personalized medicine. Understanding genetic variations helps predict drug responses, minimizing adverse effects.
Population-specific polymorphisms vary due to ancestry. African Americans have the highest number of unique polymorphisms and the smallest haplotype blocks compared to other ethnic groups. Studying genetic variations improves our understanding of disease mechanisms, drug metabolism, and personalized healthcare strategies.
Although the human genome is over 99.9% identical between non-related individuals, millions of genetic differences still exist.
Genetic variations include single-nucleotide polymorphisms, or SNPs, insertions, and deletions.
SNPs are the most common genetic variations involving single-base changes in DNA, which impact drug metabolism, influencing pharmacogenomics.
Some SNPs in noncoding regions regulate gene expression, influencing drug responses, such as reduced platelet inhibition by clopidogrel.
Multiple SNPs present together within a segment of DNA form haplotypes that are inherited together and provide deeper insights into the genetic mechanisms underlying complex diseases.
During insertions and deletions, segments of DNA are either added or removed from the genome, respectively. Smaller segments are termed indels, and larger ones are called copy number variations.
Phenotypic traits like impaired metabolism arise from inherited nonfunctional alleles.
Studying genetic variations helps personalize medicine by predicting drug responses and reducing adverse effects.
繁體中文
