Single-nucleotide polymorphism (also "snip") is a one-nucleotide (A, T, G, or C) change in a DNA sequence. They result from point mutations and in most cases do not affect the activity of genes, but in some cases they dramatically change their function. This is the basis for determining the predisposition to various diseases, as many snipes are associated with the risk of developing certain diseases. upwards
A short tandem set is the repetition of two or more pairs of directly adjacent nucleotides. For example, (TAGC)n, where n is the number of similar pairs. STR analysis is the predominant method for determining a genetic profile and is used to obtain a "genetic passport" of an individual. The study of SNPs in Y-chromosome DNA is widely used in genetic genealogy. upwards
This is the human sex chromosome, which contains the SRY gene that determines male sex as well as the genes necessary for normal sperm formation. The DNA contained in the Y chromosome is inherited from father to son, so Y-DNA analysis is widely used in genetic genealogy.
The Y chromosome is also associated with some genetic diseases that are only transmitted through the paternal line, including male infertility .
Aneuploidy is a phenomenon in which the cells of an organism contain an altered number of chromosomes that is not a multiple of the haploid set. Normally, most human cells contain 46 chromosomes, which are a diploid set (22 pairs of autosomes and two sex chromosomes). In aneuploidy, cells may have an extra chromosome (trisomy) or be missing one chromosome (monosomy). The main mechanism for aneuploidy is the improper divergence of homologous chromosomes in meiosis, resulting in two homologous chromosomes in one germ cell (resulting in trisomy) and none in another (resulting in monosomy). Aneuploidy underlies a number of human chromosomal diseases. In live births, trisomies on autosomes 8, 9, 13, 18, 21, and 22 are most common. When trisomy or monosomy occurs on other autosomes, the embryo is not viable and dies in the early stages of intrauterine development. Aneuploidy also includes anomalies in the number of sex chromosomes - polysomia on the X chromosome in men and women, monosomia on the X chromosome in women, and disomy on the Y chromosome in men. The most common are Down syndrome (trisomy on chromosome 21), Edwards syndrome (trisomy on chromosome 18), Patau syndrome (trisomy on chromosome 13), Schereshevsky-Turner syndrome (monosomy on chromosome X) and Kleinfelter syndrome (disomy on chromosome X in men). up
Alleles are different forms of the same gene that are located at the same sites (loci) on the chromosome. Since each human cell contains two sets of all genes - from the father and from the mother - the alleles determine alternative variants for the development of the same trait. If two alleles of the same gene are the same, the organism is considered homozygous for that trait. If the two alleles are different, the organism is considered heterozygous.above
Pairwise identical chromosomes, except for sex (X,U) chromosomes.
A type of inheritance in which a genetically determined disease occurs only if the mutant gene has been inherited from both parents and is not contained in the sexes (X and Y).up
Cells on the inside of the cheek.up
Amplification is the production of multiple copies of DNA from one or more copies or fragments. In cells, amplification occurs as a result of DNA replication (the process of DNA doubling), but in the laboratory it is performed using the polymerase chain reaction (PCR).above
A haplogroup is a group of similar haplotypes that also share a common snippet (single-nucleotide polymorphism). This term is widely used in genetic genealogy, where specialists distinguish Y-chromosomal haplogroups (Y-DNA, passed exclusively from father to son), mitochondrial (mtDNA, passed from mother to all children) and GCG haplogroups (large family of genes that play an important role in immune system development).up
A haplotype is a set of alleles at loci on a single chromosome, which is usually (with few exceptions) passed on as a single whole to the offspring.
A gene is a structural and functional unit of heredity that controls the development of a particular trait or property. They are regions of DNA that carry some coherent information (e.g., about the structure of a single protein molecule or a single RNA molecule).upwards
The human genome is the totality of all human genes, its complete chromosomal set. It consists of 46 chromosomes, of which 44 are sex-independent and two (X and Y chromosomes) determine sex. The chromosomes in turn contain approximately 3 billion base pairs of DNA nucleotides that form 20,000-28,000 genes.up
The human genotype is the totality of all genes, which, unlike the genome, does not characterize the entire Homo Sapiens species, but rather an individual.
An organism or cell carrying different alleles of a gene in homologous (paired) chromosomes.up
An organism or cell carrying the same alleles of a gene in homologous (paired) chromosomes.up
DNA - deoxyribonucleic acid - provides storage, transmission from generation to generation, and implementation of the genetic program of development and functioning of a living organism. DNA molecules are present in every cell of an organism and are stored as chromosomes in a special cellular structure, the nucleus.upwards
The structure of DNA consists of individual "building blocks" - nucleotides, distinguished between four kinds: Adenine (A) - Thymine (T) - Guanine (G) - Cytosine (C). In DNA, the nucleotides are joined together in pairs to form long chains. The arrangement of the nucleotides forms the sequences that are genes.up
mtDNA is DNA that is not in the cell nucleus, but in cellular structures called mitochondria, which are the cell's energy stations. The size of mtDNA is about105 times smaller than the DNA in the cell nucleus, and its peculiarity is that all progeny receive only the mother's mtDNA. This is due to the fact that the egg cell contains all cellular structures, including mitochondria, while the sperm cell carries only genetic material.upwards
Because of this property, mtDNA research has been very useful for studying human evolution: scientists were able to establish a genetic portrait of "Eve," the closest ancestor of all humans, from whom they obtained mitochondrial DNA.upwards
Deletions (from Latin deltio - destruction) are chromosomal rearrangements in which a segment of the chromosome is lost. Deletion is the loss of genetic material, and any number of nucleotides can be lost, from a single nucleotide to the loss of a large portion of the chromosome. Deletions cause some serious genetic diseases.above
A locus is the fixed position of a gene or sequence of nucleotides on a chromosome. An ordered list of loci in a genome is called a genetic map.upwards
A mutation (from Latin mutatio - change) is a persistent (hereditary) change in the genotype that occurs under the influence of the external and/or internal environment. Mutations can have either no effect on the function of DNA, or affect the molecules encoded by DNA, or partially or completely disrupt the function of certain genes.upwards
A complex chemical compound containing a nitrogenous base coupled to sugar and phosphoric acid. Nucleotides are the elementary units that make up nucleic acids (DNA and RNA) and are part of many coenzymes. There are four nitrogenous bases in DNA - adenine (A), guanine (G), cytosine (C), and thymine (T). The letters A, G, C, and T make up the alphabet of the genetic code.up
DNA sequencing is the process of determining the exact order of nucleotide bases in a DNA strand.up
Subclade - designation of a subgroup (branch) of a haplogroup. This term is widely used in the description of mtDNA and Y-DNA DNA genealogy tests.upwards
Oncomarkers are specific protein compounds whose level in human blood increases in the presence of a malignant tumor. In oncology, the determination of these compounds is used for primary diagnosis, in the process of dynamic monitoring of patients treated for early diagnosis of recurrence, as well as to evaluate the effectiveness of ongoing anti-tumor treatment.upwards
A variety of variants of gene structures (alleles) in which the rarest allele (a minor allele) occurs in the population more frequently than 1%. The most common allele is called the major allele.up
The totality of all the external and internal signs of an organism.up
Chromosomes are structures in the nuclei of cells of organisms that contain specially packed double helixes of DNA. Humans have 23 pairs of chromosomes, 22 of which are autosomal (not sex-determining) and one pair of sex chromosomes.up