Summary of this article
Basic terms related to prenatal diagnosis are explained in an easy-to-understand manner. We have compiled important keywords you need to know, such as chromosome aberrations and genetic testing.
SNP
Single Nucleotide Polymorphism (SNP) refers to a point in DNA where one base (A, T, C or G) has been replaced by another. This is a very common variation in people’s genetic information and produces genetic differences between individuals. SNPs are used in genetic research, disease risk assessment and paternity testing, and are an important tool for understanding individual genetic characteristics and health status.
STR
Short Tandem Repeat (STR) refers to a region of DNA where a short sequence of bases is repeated. For example, an STR is a region where the sequence ‘AGAT’ is repeated many times in succession; STRs are used for personal identification and paternity testing, as the number of times they are repeated varies from individual to individual. It is widely used in forensic medicine and genetics and plays a particularly important role in DNA profiling (DNA fingerprinting).
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The likelihood ratio (Likelihood Ratio, LR) is a statistical measure of how much support one hypothesis has over another. Specifically, it compares how likely a particular piece of data is to occur under a particular hypothesis when it is observed.
For example, in a paternity test, the probability that the observed genetic information occurs under the ‘parent-child relationship’ hypothesis is divided by the probability that it occurs under the ‘no parent-child relationship’ hypothesis. A higher likelihood ratio indicates that the hypothesis is better supported than the other hypotheses.
Identification of the law
‘Legal expert opinion’ refers to formal expert opinion used in legal proceedings. It is a scientific or technical investigation or analysis carried out by a court or legal body to clarify certain facts or circumstances. For example, DNA and handwriting analysis are part of legal opinion. These expert testimonies can be used as evidence in court and can have a significant impact on the verdict.
Private identification
‘Private appraisals’ are appraisals commissioned by individuals or companies and carried out without direct connection to legal proceedings or the courts. For example, this applies to appraisals carried out by the client for a specific purpose, such as paternity or handwriting appraisals. Private appraisals may also be submitted as evidence in court, but their validity and evidential value is left to the judge.
Weeks of gestation
‘Gestational week’ refers to the number of weeks since the beginning of pregnancy and is used to indicate the progress of fetal growth and development. The start of pregnancy is usually calculated from the first day of the last menstrual period, with delivery usually occurring at approximately 40 weeks. Gestational weeks are divided into early, middle and late pregnancy and are an important indicator for monitoring fetal development and maternal changes at each stage.
Gene sequence
‘Gene sequence’ refers to the order of the bases (adenine A, thymine T, guanine G and cytosine C) within a DNA molecule. This sequence determines the information the gene holds and directs what proteins the cell makes. The sequence of a gene plays an important role in determining the traits and functions of an organism, and changes in the order of these bases can alter the function of the proteins encoded by the gene.
Monozygotic twin
Identical twins are twins born from the division of one fertilized egg. This fertilized egg is the result of the union of one sperm and one egg, which then divides into two individuals by cell division. Identical twins are therefore genetically almost identical, of the same sex and very similar in appearance and characteristics. Unlike dizygotic twins, identical twins share 100% of their genetic information.
Dizygotic twin (botany)
Hermaphroditic twins are twins born when two different eggs are fertilized by two different sperm. Hermaphroditic twins share the same degree of genetic similarity as normal fraternal twins and may also differ in gender. They also often differ in appearance and characteristics from identical twins respectively. Identical twins develop simultaneously within the mother’s body but are not genetically identical.
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Supervisor of the article
Dr. Hiroshi Oka
Graduated from Keio University, Faculty of Medicine
Doctor of Medicine
Medical Doctor
