Glossary
A
Allele
Alleles are variants in the DNA that occur at a specific position on the chromosome (locus). An allele is a single copy of a genetic letter or a whole gene, inherited from one parent. A person can be heterozygous (two different alleles) or homozygous (two identical alleles) for each specific position on a chromosome. This determines what feature will be expressed in a person, for example their hair color, body height or blood group.
Amino acids
Amino acids are the basic building blocks of proteins. All Amino acids have the same basic structure: they are a large molecule consisting of carbon (C) + an amino group (NH2) + a carboxyl group (COOH) + hydrogen (H) + a variable side chain (R). The side chain determines the characteristics of a certain amino acid. There are 21 different amino acids that are used by the human body.
Autosomes
All chromosomes except the gender-specific chromosomes (X and Y) are called autosomes. A healthy human has 22 pairs of homologous autosomes and 2 sex chromosomes (females have XX, males have XY).
B
Currently our glossary holds no term starting with this letter.
C
Carcinogen
A carcinogen is any substance that promotes cancer formation. Carcinogenic substances have a toxic effect on the DNA which leads to defects in the genes that normally regulate the cell cycle. If enough of these defects accumulate in a cell, it can start reproducing uncontrollably. Such out-of-control cells are what is commonly known as cancer.
Chromosome
Chromosomes are found in the cell nucleus and are long strings of DNA tightly wrapped around special proteins called histones. In total, human body cells contain two sets of 23 chromosomes, one from each parent, resulting in 46 chromosomes in total.
CRISPR/Cas9
The CRISPR/Cas9-system is a new molecular biological method for modifying DNA with high precision and little side effects. This method makes inserting, removing and modifying DNA sequences in organisms much faster and cheaper. CRISPR/Cas9 works in all organisms.
D
DNA
The genetic information of an organism is stored and inherited as nucleic acids. Deoxyribonucleic acid, in short DNA, is a huge molecule (macromolecule). It is assembled as a double helix made up of two chains of nucleotides. The double helix structure can be thought of as a twisted rope ladder. The ladder‘s backbone is made of three components: sugar, phosphate and the rungs consist of base pairs, either adenine and thymine or guanine and cytosine.
DNA fingerprinting
DNA fingerprinting is a laboratory method to identify people by their unique DNA. The method does not look at the whole DNA but rather on a few specific positions which have different genetic letters in every human. Paternity testing and other forensic applications as well as criminal investigations all make use of DNA fingerprinting.
dominant
The term dominant describes the property of one allele over another (recessive) allele to determine the trait (phenotype) in inheritance. Dominant alleles show a phenotype in heterozygous individuals. This means that a certain dominant feature will be expressed in someone even if only one parent passed it on. It is the opposite of recessive.
E
Effect (of a SNP)
Most SNPs have no effect on health or development. But others directly influence the expression of traits or the risk of getting certain diseases. This is mostly the case when a SNP changes the building plan of a protein.
Electrophoresis
DNA, RNA, or protein molecules can be divided according to their size and electrical charge via a laboratory procedure called electrophoresis. The molecules are moved by an electric current through a gel or other matrix. It is used to accurately analyze substances such as blood or DNA.
Epigenetics
Epigenetics is the study of how your behaviors and environment can cause changes that affect the way your genes work. Unlike genetic changes, epigenetic changes are reversible and do not change your DNA sequence, but they can change how your body reads a DNA sequence.
Exon
Exons are coding regions on the DNA. This means that they are parts of the DNA which function as building plans for proteins.
F
Fluorescence in-situ hybridization (FISH)
FISH (Fluorescence - in-situ - Hybridization) is a method to visualize defined chromosome segments using a specific dye. This technique can be used to identify changes in someone’s genetic material which can lead to diseases.
G
Gene
Genes are segments of the DNA. Most genes contain information on how to build proteins, so they can be seen as a construction manual for the body.
Gene mapping
Gene mapping describes the process of determining the location of genes on chromosomes (loci) as well as the distance between these genes. This can be done using a variety of methods.
Genetic engineering
Genetic engineering, also known as genetic modification, is a technique that changes an organism's DNA using different laboratory technologies. This has been used in research and business to produce cancer treatments, genetically altered plants and other things.
Genetic letters
All the information on your DNA is encoded by sequences of four different nucleotide bases: Adenine (A), cytosine (C), guanine (G), and thymine (T). These are called the genetic letters. Different combinations of these letters can be thought of genetic codes. These encode specific instructions, for example on how to build proteins. In RNA a different base, called uracil (U), is used instead of thymine, but these letters encode the same information.
Genetic sequencing
Genetic sequencing is used in laboratories to read the DNA of a human or any other organism. The result is a long sequence of the genetic letters A, C, G and T representing the whole genome of this person. This information can be used to determine specific genetic characteristics, for example if a person has a genetic variation that increases the risk for breast cancer.
Genetically modified organism
Genetically modified organisms (GMOs) are organisms whose genetic makeup has been purposely altered using genetic engineering methods.
Genome
The genome is defined as the totality of our genes, meaning the total genetic material of a cell. The human genome consists of DNA which is stored on 46 Chromosomes in the cell nucleus. Nearly every cell in the body has a complete copy of the genome. All genetic information the human body needs to grow and develop is stored in the genome.
Genomics vs. Genetics
Genetics analyzes the functioning and composition of the single genes whereas genomics addresses all genes and their relationships in order to identify their combined influence on the growth and development of the organism.
Genotype
The genotype describes the genetic information of an organism. You cannot see the genotype from the outside, as you can’t see the DNA directly. But the genotype determines how an organism develops. This in turn leads to observable differences which is referred to as a person’s phenotype. However, different genotypes don’t need to result in different phenotypes. This is mostly the case if genotypes are silent (e.g., not changing the resulting protein) or if they affect non-coding DNA. Example: Let’s say your mum has blue eyes, which we’ll refer to as B from now on and you dad has green eyes, which is going to be b for us now. B and b in this case are the alleles. For these two alleles there are three possible pairings: BB, Bb, bb You can refer to these pairings in two different ways: genotype and phenotype. The genotype indicates the exact pairing of alleles. So, either BB, Bb or bb. It has nothing to do with the expression of the trait, meaning the eye color in this case. The genotype describes the genetic information of an organism. You cannot see the genotype from the outside, as you can’t see the DNA directly.
H
Haploid - diploid
There are two types of cells in the body - haploid cells and diploid cells. The difference between haploid and diploid cells is related to the number of chromosomes that the cell contains. Most human body cells are diploid cells, which contain two complete sets of chromosomes. Sex cells like sperm and eggs, also called germ cells, are haploid and thus contain only one set of chromosomes. A diploid set of chromosomes results from the fusion of two haploid sets of chromosomes at fertilization (egg and sperm).
Heredity
Heredity is the transmission of genetic characteristics from parents to their children before they are born. An example for inherited characteristics in humans is eye color.
heterozygous
A homologous chromosome is a pair of two chromosomes – one from the father, one from the mother. Heterozygous means that both alleles on a specific position on the homologous chromosomes differ from each other. In heterozygous individuals, one allele is dominant (displayed with a capital letter e.g. A) and one is recessive (displayed with a small letter e.g. a), so in this example, in the end we have Aa. The dominant allele is the one that will be expressed. For example, being heterozygous for a recessive trait like blue eyes means that it is unlikely to develop those. Being homozygous for this trait, on the other hand, means that you will have blue eyes.
Histones
Histones are basic proteins that bind to DNA and give the chromosomes their shape. They function as spools for the DNA strings to wrap around.
homozygous
A homologous chromosome is a pair of two chromosomes – one from the father, one from the mother. Homozygous means that both alleles on the homologous chromosomes are the same. In homozygous individuals, the alleles can either both be dominant (displayed in capital letters e.g. AA) or both recessive (displayed in small letters e.g. aa). For example, being heterozygous for a recessive trait like blue eyes means that it is unlikely to develop those. Being homozygous for this trait, on the other hand, means that you will have blue eyes.
I
Inheritance
Inheritance is the process by which genetic information is passed down from parents to their children and further on to subsequent generations during reproduction. It is the reason why some family members have similar characteristics.
Intron
Introns are noncoding regions within the DNA. This means that they are parts of the DNA which do not function as building plans for proteins.
J
Currently our glossary holds no term starting with this letter.
K
Karyotype
An individual's entire set of chromosomes is known as their karyotype. The term can also refer to an image created in a lab showing a person's chromosomes isolated from one cell and organized in numerical order. A karyotype can be used to check for chromosomal number or structural problems. For example, Down syndrome (also called trisomy 21) is detectable by looking at a person’s karyotype – with this specific syndrome, chromosome 21 is present three times, instead of two times.
L
Locus
The physical location of a gene on a chromosome is called gene locus, which is somewhat like a street address. Different variants of a gene at a specific locus are called alleles.
M
Major Allele “Reference-allele“
The major allele is the most common allele in the population.
Microarray Technology
"Microarray is a collective term for various examination systems that allow the parallel analysis of several thousand individual detections in a small amount of biological sample material. There are various forms of microarrays, which are sometimes also referred to as "gene chips" or "biochips" because, like a computer chip, they can contain a lot of information in a very small space."
Minor Allele
A minor allele is a less common allele. The MAF (minor allele frequency) tells you how common an allele is in the population.
Mitochondrial DNA
Mitochondria are referred to as the „powerhouses“ of the cell. They produce ATP, a molecule that provides energy to the cell. Mitochondria have their own DNA, the mtDNA, which is located in the cell fluid (cytoplasm) independent from the DNA in the cell nucleus.
Mitochondrion
The mitochondrion is known as “the powerhouse of the cell” and that is for a reason. It produces ATP, a molecule that provides energy to the cell. Mitochondria are so called “cell organelles”, which means every cell in your body has them.
mRNA
The mRNA (messenger RNA) is very important for the process of building a new protein. In this process there are two main phases: the transcription of DNA and the subsequent translation into a chain of amino acids. The mRNA is like a copy of one strand of the DNA which can be read by the protein factories (ribosomes) in the cells. mRNA gives the ribosomes the information on how to create a specific protein.
N
Nanopore sequencing
Nanopore sequencing is one method for DNA sequencing. It is used to determine an individual’s specific DNA composition. The method works by measuring the voltage change during the transport of DNA through a tiny pore across a membrane. Different voltages occur because each the base for each genetic letter (A, C, G, T) has a different electric conductivity.
Nucleic acid
Nucleic acids are very big molecules, so called macromolecules that are crucial to all forms of life. For us they are most commonly known as DNA or RNA. Nucleic acids are built from nucleotides, which are molecules consisting of a sugar, phosphate and one of the five bases adenine, guanine, cytosine, thymine (in DNA) or uracil (in RNA).
Nucleotides
Nucleotides are the basic building blocks of nucleic acids (i.e. DNA and RNA). They are molecules consisting of a sugar, phosphate and one of the five bases adenine, guanine, cytosine, thymine (in DNA) or uracil (in RNA).
O
Odds ratio
An odds ratio, in short OR, is a statistic measure of an association between a genetic change and an outcome. We calculate the probability that an event occurs divided by the probability that event does not occur. If the OR > 1 we can say that the event probability is higher compared to reference category. If OR < 1, the event probability is lower compared to reference category.
Organelle
If a cell had organs, the organelles within a cell would function as such. Organelles are specialized subunits in a cell that fulfill different functions to keep the cell and thus your body to stay alive.
Organism
When we talk about an organism, we mean an organic, living system that is made up from cells and functions as an individual entity.
P
Phenotype
In contrast to the genotype, the phenotype describes the physical/ biochemical/ physiological appearance of an organism. It can be seen as the product of the genotype combined with environmental factors. Some examples would be the eye or hair color of an individual as well as physiological characteristics such as allergies or blood groups.
Protein
Proteins are large complex molecules that are essential to the structure, function and regulation for your body’s organs and tissues. Proteins help your body carry out all of the chemical reactions it needs to keep you alive. They are responsible for most of the processes in cells and are built from amino acids, which on the other hand are made up from the DNA’s building blocks, the nucleotides.
Protein biosynthesis
Protein biosynthesis is the process of a cell building a protein.
Q
Currently our glossary holds no term starting with this letter.
R
recessive
In genetics, the term recessive describes the property of an allele to be less expressed than the other allele. Recessive alleles show a phenotype only in homozygous individuals. This means that a certain recessive feature will only be expressed in someone who has inherited it from both parents. It is the opposite of dominant.
Recombinant DNA technology
With this technique, scientists can combine DNA from several species or produce genes with new functions. The new DNA copies made in this process are called recombinant DNA. The method uses enzymes and a variety of laboratory procedures to modify and isolate specific DNA sequences.
Restriction fragment length polymorphism (RFLP)
Restriction fragment length polymorphism (RFLP) is one laboratory method to determine an individual’s genetic material. It is commonly used to study complex genetic diseases that are associated with single nucleotide polymorphisms (SNPs).
Ribosome
Ribosomes are the protein factories of the cell. Ribosomes use amino acids delivered by tRNA and the information encoded in mRNA to build proteins. Proteins are long, folded chains of amino acids.
RNA
Ribonucleic acid, in short RNA, is a nucleic acid similar to DNA, with the difference that it is only one single strand. Like DNA, it is composed of so-called nucleotides based on sugar, phosphate and bases (adenine + uracil, guanine + cytosine). There are various types of RNA with different functions. All of them are important for the creation of a new protein in a process called protein biosynthesis.
rRNA
The rRNA (ribosomal RNA) forms the main structural and functional units of ribosomes, the protein factories of cells.
S
SNP
An SNP (single nucleotide polymorphism) is the most common type of genetic variant. It describes the exchange of one genetic letter for another. For example, an SNP may replace cytosine (C) with thymine (T) in a certain segment of DNA.
T
Transcription
The first step in creating a new protein is called transcription. In this process, the cell creates a copy of one strand of its DNA, which is called RNA. This copy is then used to produce a new protein. This is done in the next step, the translation.
Translation
Translation is the final step in creating a new protein. In the translation phase, the protein is built based on the information contained by the RNA strand created in the prior phase (transcription). Short sequences of three nucleotides (“genetic letters”) on the RNA strand encode one specific amino acid. The order of this three-letter sequences describes the arrangement of amino acids in the protein. The factories of the cell (ribosomes) use this information to create chains of amino acids which later fold to create the final protein. In a nutshell, we could say that RNA language (nucleotides) is translated into protein language (amino acids).
tRNA
The tRNA (transfer RNA) is responsible for transporting the building blocks of proteins (amino acids) to the protein factories (ribosomes) in the cells.
U
Currently our glossary holds no term starting with this letter.
V
Variants
A genetic variant is a permanent change in the DNA. DNA sequence variations between individuals or populations are referred to as genomic variation. While some variations have no biological consequences, others do affect biological function (for example, a mutation that leads to a genetic disease).
Virus
A virus is a very small piece of organic material. Viruses reproduce by entering living cells of humans, animals, plants, or bacteria. The virus then inserts its own genetic information into the cell’s DNA. This causes cells to produce copies of the virus. As a result, the cell can’t fulfil its normal functions and eventually dies. Humans and animals experience this process as disease. Viruses can’t reproduce on their own.
W
Currently our glossary holds no term starting with this letter.
X
Currently our glossary holds no term starting with this letter.
Y
Currently our glossary holds no term starting with this letter.
Z
Currently our glossary holds no term starting with this letter.