What are genes?
Genes are the information written in the human hereditary material (DNA) and are of utmost importance for the growth and development of an individual. They located in 23 pairs of human chromosomes. Chromosomes appear in pairs; one comes from the mother and the other one from the father. Thus, every person has two copies of a gene. One copy is called an allele. The two alleles can be identical or different.
What is written in the genes?
Genes play an essential role in passing hereditary characteristics from one generation to the next. Since they are passed from parents to their children, they are responsible for the similarities between parents and children, and for the creation of new human beings. The products of the genes are proteins which are the main macromolecules in the organisms. Proteins are comprised of 20 different smaller molecules called amino acids; the genes encode the correct amino acid sequence and the information on the amino acid type. The specific amino acid sequence encoded by a gene results in a specific protein. In this way, the genetic code, together with the environmental influences, forms the uniqueness of each individual.
How is the information written in the genes?
Information in a gene is written as a specific sequence of four different molecules called nucleotides. They are denoted by the letters C, G, A and T. The recent decoding (sequencing) of the human genome thus offered an approximately 3 billion long sequences of these four nucleotides. They are linked into a chain, called the DNA or the double helix. In humans it is divided into 23 shorter parts called the chromosomes. Genes are specific DNA regions containing such nucleotide sequence that can be recognized by the cells to make a corresponding protein. There are approximately 30,000 genes in a human DNA sequence. A protein is also a sequence of a different type of molecules called amino acids, which are interlinked based on the DNA sequence. So to speak, a gene is a plan for protein production; a cell uses its mechanisms to translate the nucleotide sequence into an amino acid sequence. In the final analysis, proteins are large molecules used by the cell for its framework, communication and regulation of chemical reactions.
Each cell's nucleus contains the entire DNA sequence in two copies (one from each parent). Thus, each cell is capable of making every protein found in the human body (i.e. it has all the genes to do so), but the majority of them are never needed. DNA, analysed by GenePlanet, is contained in the cells of oral mucosa that broke away to swim freely in the saliva. These cells are not abundant; however, modern laboratory techniques of isolation and DNA multiplication allow us to obtain quality results from even the tiniest sample.
What are mutations?
In Latin, mutation means change. When talking about mutations in genetics we talk about the change in the DNA sequence. This can happen in many ways—a nucleotide can be inserted into the sequence, it can be deleted or simply substituted by another one. We call such a substitution a SNP. All SNPs were thus created by some mutation. If a mutation occurs in a certain gene, the gene can become inactive (it does not make the correct proteins) or, rarely, make a new and better protein. In this way, an organism with a different trait is created, having a selective advantage for survival. Thus, mutations are DNA "errors" which appear by chance, and at the same time represent the engine of evolution.
What are association studies?
Many diseases with a genetic component are characterized by the influence exerted by different genes, increasing the susceptibility of an individual to a certain disease. Association studies are used to discover the genes responsible for this increased susceptibility. These studies compare:
- The genetic code of a larger number of individuals with a specific disease,
- With the genetic code of the disease-free individuals.
If special markers in the genetic code are discovered in this analysis, it can be concluded that they are linked with the increased chance for the appearance of the disease. One such marker is the SNP.
How to understand association studies?
The links between SNPs and genes, revealed by the association studies, are reliable only in the tested populations. However, in general it can be concluded that the Caucasian population in Europe and America is homogenous enough to extrapolate the results of the association studies within this population.
Special care should by all means be taken when dealing with different races. The links between SNPs and genes in one race may not be identical to those in another race. The reason for it lies in the separate development of the human races throughout the centuries.
How to understand the results of the personal genotyping?
In a human genome, there are 30,000,000 known spots where different nucleotides appear in individual people. We call these loci SNPs. Most SNPs have no association with diseases and individual traits and are randomly inherited. Some others, however, are associated with specific gene forms which cause the appearance of a disease. Since the SNP analysis technology has advanced so much as to be able to analyze many 100,000 at the same time, it is possible to single out those SNPs which are linked with certain diseases ( this is accomplished with association studies).
GenePlanet employs the same techniques to check your genome. By using the results of the analysis and the association studies data we can foretell your talents, your response to medications and your predisposition to certain diseases.
What are SNP mutations and what is their meaning?
SNP (single nucleotide polymorphism) is a substitution of one nucleotide by the other, and it is pronounced "snip". It is the part of the DNA sequence which suffered a point mutation in the past; there was a substitution of one nucleotide in the sequence, for example, instead of nucleotide C, nucleotide A, G or T was inserted (e.g. CCGGA → CAGGA). Thus, people now have different nucleotides in these locations, which also makes us different from each other. Identical twins have identical SNPs in all loci. Since we possess two DNA chains (one from the mother, the other from the father), they may either contain identical nucleotides or different nucleotides. SNPs are useful because of their association with disease occurrence, carrying an important predictive value of the risk of disease development in a person.
Example:
In a known locus in the genetic code, there is a SNP and a gene which is responsible for baldness in its vicinity. If nucleotide C is located on the SNP locus, there is an influential form of the gene for baldness in its vicinity. Throughout generations, both were passed on together due to their physical proximity. If, however, nucleotide T is found on this SNP locus, a form of the gene that does not cause baldness will likely reside in its vicinity. To foretell baldness it thus suffices to know whether a person has nucleotide C or T in the SNP locus. It must be stressed, however, that due to paired chromosomes, SNPs and their corresponding genes are passed on in pairs as well. It is only such a pair or genotype that offers information on the probability of the appearance of a certain trait.
How is SNP used?
In the human genome there are around 30,000,000 loci with variations or substitutions of individual nucleotides called SNPs. Some of these substitutions, appearing on known loci in the genetic code, may be associated with certain traits or predispositions to certain diseases.
SNP may be located in an area of the gene or in the vicinity of its associated gene. SNP usually does not cause disease. It is merely a change in a certain locus of the genome that has been shown by the association studies to be linked with the appearance of disease. Thus, the information about the SNP type in a certain locus of the genetic code itself suffices for the calculation of the probability of disease appearance. We do not need to know the disease-causing gene or its function.
How do genes influence the appearance of disease?
Due to constant DNA replication (every cell in our bodies must undergo this; cells duplicate throughout our lifetime), certain factors in the environment or in the cell itself may bring about an error in the genetic code. The gene malfunctions if there are many such errors in the code or if an error occurs in a critical location. The product obtained by gene transcription no longer performs its duties as well as before or not at all. The result may be the appearance of disease.
If mutation occurs in a certain gene, there are three different consequences. It may be beneficial, conferring advantage to the individual; neutral with no consequence to the individual's functions, or harmful where changes cause negative events such as disease states. If the change occurs in a region outside the gene, protein production is usually not affected. A mutation may, however, affect the regulatory areas of the gene which leads to gene over-expressivity or gene silencing. Generally harmless mutations in the non-coding region between the genes which cause the absence of intron splicing can also be consequential.
Disease can be brought about by any disturbance in gene expression and thus protein production.
Does SNP tell the absolute truth?
By knowing the SNPs we can figure out the probability of a disease appearing based on the genetic code. Such a value can be low or high for an individual. Eaven though we are dealing with probabilities with scientifically backed statistics, knowing the SNPs cannot give an absolute prediction whether someone will acquire a certain disease or not.
What is the SNP applicability then?
Knowing SNPs is not some magic ball that can foretell future. But their knowing is still a scientifically based starting point for determining probabilities of disease development. What is the SNP applicability then? Because there are genes and environment that affect humans, genetically based risks can be minimised by an appropriate life style. Where SNPs show increased risk for disease development, attention can be focused in a matter of watching for external risk factors and increasing preventive measures. This is what personalised genetics enables us to do. Knowing your own genome and thus knowing yourself gives you opportunity to choose a life style that will minimise risk for potential disease development.
Why do we want to know the probability of acquiring a disease if it can appear despite there being only a low chance for it? Because if the probability is high, we shall pay more attention to the risk factors which may lead to the appearance of the disease. That is what lifestyle-altering personalized genetics can do for us. It brings on lifestyle changes—changes in the form of preventive actions to avoid certain diseases. Knowing your own genome and thereby knowing yourself gives you the opportunity to act responsibly and decide on a lifestyle that will minimize the risk of developing potential diseases.
What can GenePlanet tell me about my ancestry?
Man first appeared in Africa and then migrated away, populating the entire world. During migrations, groups of people formed which inhabited various areas of the world and did not remain in contact with each other. Despite the fact that man appeared 130,000 years ago, from a genetic viewpoint we are a rather young species without major changes having occurred in the human genome, for mutations occur slowly. Human beings thus posses genomes that are mostly identical, with only minor variations. These variations are the result of the separate habitats of the groups in the world which thus developed differently. Each group was affected by a different environment which favoured different development than in other parts of the world.
Due to these little differences among the ethnic groups, GenePlanet and its SNP method can reveal your share of similarity with an individual group. Exact information on ancestry is not available; it is, however, possible to find out to what extent you belong to a certain group, thus offering you information on your ancestry in the broader sense of the word.