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Formerly known as European Learning Laboratory for the Life Sciences

Our inspiring educational experiences share the scientific discoveries of EMBL with young learners aged 10-19 years and teachers in Europe and beyond. We belong to EMBL’s Science Education and Public Engagement office.

SEPE glossary of biological terms

From A like “Accession number” to Z like “Zinc finger nuclease”, the SEPE glossary contains definitions of a growing number of terms related to biological terms and research in the life sciences.

  • Accession number
    A unique, shorthand and stable identifier is given to individual entries in databases. It allows you to track different versions of that record over time and also to jump between information in different databases related to the same entity.
  • Affinity Chromatography
    A method used to separate biochemical mixtures (such as protein mixtures) on the basis of a highly specific interaction (e.g. antigens binding to antibodies, or his-tagged proteins binding to metal ions).
  • Allele
    One of a set of alternative forms of a gene. In a diploid organism, a gene has two alleles, each occupying the same position (locus) on homologous chromosomes.
  • Alpha-helix (α-helix)
    Alpha-helix describes a structural motif of secondary structure found in proteins. An alpha-helix is a polypeptide chain folded into a coiled (spring-like) structure. The helical twists are stabilised by hydrogen bonds between the NH- and CO-groups of the individual amino acids. In particular, this intramolecular hydrogen bonding occurs between the NH-group of one amino acid and the CO-group of the 4th amino acid away from the first. The alpha-helix is the most common structural motif in proteins, followed by the beta-sheet.
  • AlphaFold
    An artificial intelligence (AI) algorithm which can predict a protein’s three-dimensional structure based on its amino acid sequence.
  • Amino acids
    Small organic molecules that are the building blocks of proteins. In humans, there are 20 different amino acids that can be combined in various sequences to form a wide variety of proteins.
  • Amygdala
    An almond-shaped area in the midbrain that is involved in the experience of emotions.
  • Annealing (PCR)
    The second step in the polymerase chain reaction (PCR) cycle. In this step, primers bind to the DNA template.
  • Annotation
    The process of attaching additional information about a data entry, for example, a gene sequence or protein sequence. Annotations can be structural (for example, identifying a protein-coding region) or functional (for example adding biological information about the function of a protein). Annotation can also refer to the whole entry (an entire protein) or a particular feature (a protein domain). Annotation can be performed automatically or manually by curators.
  • Astex Viewer
    Java-based viewer which allows to visualise three-dimensional structural information on macromolecules. For example, it is used to view pdb-files of three-dimensional protein structures.
  • Artificial Intelligence (AI)
    The field of computer science focused on developing machines and computer systems that can perform tasks that would typically require human intelligence, such as problem-solving, learning, and decision-making.
  • Balls and sticks representation (molecular structures)
    A “balls and sticks representation” is a graphical representation of the three-dimensional structure of macromolecules. The atoms are represented as “balls” and their connecting covalent bonds are represented as lines or “sticks”. Compare to “sticks representation”.
  • Beta-sheet (β-sheet)
    Beta-sheet (or beta-pleated sheet) describes a structural motif of secondary structure found in proteins. Beta-sheets are made of multiple beta-strands – polypeptide chains which have an almost fully extended shape. Multiple beta-strands are formed into beta-sheets by hydrogen bonds between strands. In particular, this intermolecular hydrogen bonding occurs between the NH-group of individual amino acids in one strand and the CO-group of individual amino acids in the adjacent strand. The beta-sheet is the second most common structural motif in proteins after the alpha-helix.
  • Bioinformatics
    The science of storing, retrieving and analysing large amounts of biological information.
    The Basic Local Alignment Search Tool (BLAST) is a kind of a ‘Google’ search for finding regions of similarity in nucleotide or amino acid sequences. A BLAST search enables you to compare a query sequence with a library or database of sequences, identifying sequences in the database that resemble the query sequence.
  • Bone marrow stem cells

    The bone marrow is a stem cell niche for haematopoietic stem cells and mesenchymal stem cells, which have the ability to form bone (as well as cartilage and fat).

  • Brainstem
    An area in the lower brain which consists of the midbrain, pons and medulla. The brainstem has various functions including the regulation of the central nervous system.
  • Buffer
    An aqueous solution containing salts and other reagents that is used to keep the pH constant in (bio)chemical reactions.
  • Cas9 nuclease
    An enzyme which is associated with CRISPR and cuts DNA by generating double breaks.
  • Cell
    A cell (Latin cella: “small room”) is the basic structural, functional, and biological unit of all living organisms.
  • Cerebral cortex
    he outer layer of neurons covering the brain’s hemispheres. The cerebral cortex is involved in higher-order functions such as language and information processing.
  • Cheminformatics
    The chemical equivalent of bioinformatics; the application of computer science to chemical data, for example, the storage, indexing and searching of chemical compound data.
  • Chromophore
    A chemical group responsible for giving a compound a particular colour by exciting at a specific wavelength of light.
  • Chromosome
    Packaged and organised structure which contains most of the DNA of a living organism. Humans have 22 pairs of autosomes and 1 pair of sex chromosomes (XX in women and XY in men). Humans have 22 pairs of autosomes and 1 pair of sex chromosomes (XX in women and XY in men).
  • ClustalW
    Programme which aligns multiple sequences of nucleic acids or amino acids.
  • Computational biology
    The development and application of analytical methods, mathematical modelling and computational simulation to the analysis of biological data and study of biological systems.
  • Consensus gene sequence
    A sequence that is conserved and may be found multiple times in a genome and also in other species. Consensus sequences show a common function between species. The sequence can show some minor variability but will have some core unchanging residues. A consensus sequence is obtained by aligning the results of multiple sequences from a particular site and identifying the sequence that represents the most commonly found nucleotides at each position.
  • Convergent evolution
    Process by which organisms, taxa, or other biological units (e.g., genes or proteins) that are not derived from a common ancestor have independently acquired comparable (analogous) traits. Convergent evolution can be the result of adapting to, e.g., the same ecological niche, or can be the result of other selective pressures.
  • CRAM
    A framework technology combining highly efficient reference-based compression of sequence data with a data format that is directly available for computational use.
    Clustered regularly interspaced short palindromic repeats are segments of bacterial DNA containing short and repetitive base sequences.
  • Cryogenic Electron Microscopy
    An electron microscopy technique that uses samples that are cooled at very low temperatures to study the structure of biological macromolecules, such as proteins.
  • Curation
    In the context of biological databases, curation is the process of interpreting and representing biological data using standardised annotation, controlled vocabularies and standardised formats, so the data can be stored and made available.
  • Deletion
    Mutation where part of the gene is deleted.
  • Denaturation (PCR)
    First step in the polymerase chain reaction (PCR) cycle. In this step, the double-stranded DNA separates into single strands.
  • Deoxynucleotide triphosphate (dNTP) (PCR)
    In a polymerase chain reaction (PCR), deoxynucleotide triphosphates (dNTPs) consist of a mixture of deoxyadenosine triphosphate (dATP), deoxyguanosine triphosphate (dGTP), deoxycytidine triphosphate (dCTP), and deoxythymidine triphosphate (dTTP) to supply the PCR reaction with free nucleotide building blocks.
  • Deoxyribonucleic acid (DNA)
    A molecule that carries the genetic instructions for the development, functioning, and reproduction of all known living organisms. DNA is primarily located in the cell nucleus and consists of a double helix structure made up of nucleotides. These nucleotides consist of the sugar deoxyribose attached to a phosphate group and a nitrogen-containing base (adenine, cytosine, guanine, and thymine).
  • Dimer
    The term dimer describes the quaternary structure of a macromolecule made of two (di) subunits. A homodimer contains two identical subunits, while a heterodimer is made of two different subunits.
  • Diploid
    Cell nucleus containing two complete sets of chromosomes, one from each parent.
  • Distributed Annotation System (DAS)
    The Distributed Annotation System defines a protocol that is used to exchange biological annotations relating to biological entities (such as genomic regions). DAS allows a single machine to collate sequence annotation information from multiple distant servers and display it to the user in a single view, on an as-needed basis.
  • Divergent evolution
    Process by which organisms, taxa, or other biological units (e.g., genes or proteins) that are derived from a common ancestor have independently acquired distinct traits. Divergent evolution can be the result of adapting to, e.g., different ecological niches, or can be the result of other selective pressures.
  • DNA
    Deoxyribonucleic acid (DNA) is the hereditary genetic information of living organisms, and is composed of four types of bases: adenine (A), cytosine (C), guanine (G), and thymine (T).
  • DNA barcoding
    DNA barcoding is a molecular method for species identification of living organisms. The basis of this method forms so-called DNA barcodes – marker genes about 300-600 nucleotides in length. Similar to industrial barcodes which identify specific products in the shop, DNA barcodes are used to discriminate between species within a group of living organisms.
  • DNA polymerase
    Enzyme which synthesises DNA from nucleotide building blocks.
  • DNA repair
    Collection of processes by which a cell identifies and corrects damage to the DNA molecules which encode the genome.
  • DNA replication
    The process of making an identical copy of double-stranded DNA by using an existing strand of DNA as a template to make a new one.
  • Double strand break
    Process in which both strands in the DNA are cut. They are hazardous to the cell because they can lead to rearrangements of the genome.
  • DNA Sequencing
    A technique to determine the sequence of bases (adenine, cytosine, guanine, and thymine) in a DNA molecule. DNA sequencing helps scientists understand the genetic information encoded in DNA and study variations among individuals and species as well as the evolution of species.
  • Electron microscope tomography
    Used to obtain detailed 3D structures of subcellular structures and multi-component (for example, protein) complexes.
  • Elongation (protein synthesis)
    In the second phase of protein synthesis, the following happens: tRNA carrying the correct amino acid binds to the ribosome and the new amino acid forms a peptide bond with the growing polypeptide chain. Elongation is preceded by initiation and followed by termination.
  • EMBOSS Needle
    Tool to align two nucleotide sequences (pairwise alignment).
  • EMBOSS Seqret
    Tool which can be used to reverse complement a nucleotide sequence.
  • EMBOSS Transeq
    A tool which translates nucleic acid sequences to their corresponding peptide sequences.
  • Endocrine signalling

    This encompasses long-distance signalling between organs and is mediated by hormones which travel in the bloodstream.

  • Ensembl
    An online portal providing freely available genome information and automatic annotation of vertebrate genomes. Ensembl is a joint project between the EMBL-EBI and the Wellcome Trust Sanger Institute.
  • European Nucleotide Archive (ENA)
    Database providing a comprehensive record of the world’s nucleotide sequencing information, covering raw sequencing data, sequence assembly information and functional annotation. ENA is made up of a number of distinct databases that include EMBL-Bank, the Sequence Read Archive (SRA) and the Trace Archive.
  • Evolution
    The process by which species change over time. It occurs through the accumulation of genetic variations in populations, leading to the emergence of new species and the extinction of others. Evolution is driven by processes such as natural selection, genetic drift, and mutations.
  • Extension (PCR)
    The third step in the polymerase chain reaction (PCR) cycle. In this step, the DNA polymerase starts making a new strand of DNA by adding nucleotides in sequential order.
    The FASTA format is a text-based format to display and store nucleic acid sequences (DNA and RNA) and amino acid sequences (protein). Each sequence starts with a single line containing a greater-than sign (>) and a descriptive header (this is the name of the sequence). The name of the sequence is added without introducing a space. FASTA information may be stored in .fas, .seq or .txt files, the two latter ones of which can be opened and edited using a basic text editor (e.g. Windows NotePad or Mac TextEdit).
  • Fluorescence
    The emission of electromagnetic radiation from a substance which occurs when the substance is exposed to electromagnetic radiation of a different wavelength (such as ultraviolet light or X-rays).
  • Fluorescent tag
    Fluorescent protein that is widely used to tag proteins of interest to make them visible under the microscope.
  • Genome
    The complete set of genetic material (DNA) present in an organism or a cell. The genome contains all the instructions necessary for an organism’s growth, development, and functioning. In humans, the genome consists of 23 pairs of chromosomes that are all located within the cell nucleus.
  • Haematopoiesis
    This is the process of blood cell formation. It starts with multipotent haematopoietic stem cells, goes through multipotent progenitor cells and ends with specialised daughter cells. It mainly happens in the bone marrow.
  • Heterotetramer
    A protein made up of four (hence tetra) subunits, where the chains are not identical (indicated by hetero).
  • Heterozygous
    Having two different forms of alleles.
  • His-tag
    A polyhistidine tag (his-tag) is an amino acid motif made of (usually) 6 histidine amino acids which are added to one end of a recombinant protein to allow purification of the protein by affinity chromatography.
  • Homeostasis

    This is the situation where a balance is reached between an organism’s or cell’s internal and external environments.

  • Homologous recombination
    A type of genetic re-organisation in which nucleotide sequences are exchanged between two similar or identical molecules of DNA.
  • Homologue
    Biological units (e.g., genes or proteins) are homologues if their feature of interest (e.g., sequence, structure, or function) is identical or very similar and they originate from the same ancestral biological unit (common ancestor). Homologues can either be paralogues or orthologues.
  • Homotetramer
    A protein made up of four (hence tetra) subunits, where the chains are identical (indicated by homo).
  • Homozygous
    Having two identical alleles.
  • Hormone

    A small protein molecule which organs use to communicate with each other and to control the body’s response to an internal or external requirement. An example is the hormone insulin, which regulates the blood glucose level. It can even regulate erythropoietin, which is involved in controlling the oxygenation levels of blood by red blood cells.

  • Hypothalamus
    An area in the brain located below the thalamus and just above the midbrain region of the brainstem. The hypothalamus controls the autonomic nervous system and the secretion of hormones by the pituitary gland.
  • Initiation (protein synthesis)
    In the first phase of protein synthesis the following happens: positioning of ribosome on mRNA, binding of first tRNA, and association of the large and small ribosomal subunit. Initiation is followed by elongation and termination.
  • Insertion
    Mutation where one ore more nucleotides are inserted into the genomic DNA.
  • JalView
    Java-based bioinformatics tool which allows to visualise, analyse and edit multiple sequence alignment.
  • Jmol
    A free, open source molecule viewer based on Rasmol but written in Java.
  • Juxtacrine signalling

    This refers to the communication between cells that are direct neighbours. It usually occurs via specific proteins of the two cells.

  • Karyogram
    Depiction of the chromosomes of a cell, arranged in homologous pairs and in a numbered sequence.
  • Karyotype
    Full set of chromosomes of a cell arranged with respect to size, shape and number.
  • Large ribosomal subunit
    The large ribosomal subunit contains the peptidyl transferase centre (PTC), where amino acids are incorporated into the growing peptide chain by peptidyl transfer.Ligand
  • Ligand
    A substance that specifically and reversibly binds to a biomacromolecule to form a larger complex and alters its activity or function.
  • Locus
    The position of a gene on a chromosome. The term locus is usually restricted to positions of genes which are expressed.
  • Macromolecule
    A large molecule, frequently made up of smaller subunits. Usually refers to nucleic acids, proteins, carbohydrates and lipids.
  • Malignant melanoma
    A type of skin cancer that originates in melanocytes, specialised pigment cells. The main cause of malignant melanoma is overexposure to UV light.
  • Mastermix (PCR)
    In a polymerase chain reaction (PCR), a mastermix is a solution containing all reagents (except DNA template and primers) required to make new strands of DNA by PCR. A typical mastermix contains DNA polymerase, free nucleotides and reaction buffer.
  • Membrane topology
    Location of a protein or protein domain with respect to the cell’s membrane. For example, its membrane topology describes whether the protein/domain is located in the cytosolic side, non-cytosolic side, or is integrated into the membrane (transmembrane).
  • Messenger RNA (mRNA)
    The mRNA contains the transcribed copy of a specific DNA sequence; its role is to transport the information stored in the DNA to the site of protein synthesis, where it can be translated into an amino acid sequence.
  • Metastatic
    Referring to metastasis where a tumour or cancer spreads from its site of origin to more distant tissues and organs.
  • Multiple sequence alignment
    Alignment of three or more biological sequences (nucleic acid or protein) for the purpose of comparing these sequences.
    MUltiple Sequence Comparison by Log-Expectation (MUSCLE) is a tool to align and compare multiple sequences, particularly suitable for amino acid sequences.
  • Mutation
    Any permanent change or alteration in the genetic material that changes the nature of the product made under the direction of that gene.
  • Myelodysplasia
    Myelodysplastic syndromes are disorders affecting the production of blood cells derived from bone marrow.
  • Neural circuit
    A group of interconnected neurons which function together as a unit. A functional neural circuit comprises three parts: sensory input, information processing, and motor output. An example of a simple neural circuit is the knee-jerk reflex.
  • Next-generation sequencing
    Sequencing technologies that produce thousands of sequences simultaneously. Post-sequencing, this requires that multiple stretches of short sequence (sequence reads) are assembled together. This is done based on overlapping areas of sequence.
  • Non-homologous end joining
    A pathway that repairs double-strand breaks in DNA. “Non-homologous” refers to the fact that the break ends are joined without the need for a homologous template (in contrast to “homology directed repair”, which requires a homologous sequence to guide repair).
  • Nuclear magnetic resonance (NMR) spectroscopy
    A spectroscopy technique that uses the magnetic properties of atomic nuclei to determine the physical and chemical properties of atoms or molecules. NMR spectroscopy has been particularly important for resolving the high resolution 3D structures of proteins.
  • Nucleotide
    Basic building block of nucleic acids such as DNA and RNA. DNA nucleotides are made of pentose sugar (deoxyribose), phosphate group(s), and a base (either adenine, thymine, cytosine, or guanine). RNA nucleotides are made of pentose sugar (ribose), phosphate group(s), and a base (either adenine, uracil, cytosine, or guanine).
  • Nucleotide BLAST
    Nucleotide Basic Local Alignment Search Tool is a tool which searches nucleotide databases using nucleotide sequence query. It identifies regions of local similarity between nucleotide sequences and can thus be used to find the identity of unknown nucleotide sequences in the database.
  • Nucleus
    The nucleus (Latin nucleus/nuculeus: kernel/seed) is a membrane-enclosed organelle found in eukaryotic cells, which contains most of the cell’s DNA.
  • Open reading frame (ORF)
    Region in a sequence of nucleotide triplets which starts with a start codon and ends with the next stop/termination codon. All open reading frames can potentially be translated into a protein. However, in eukaryotes, the open reading frame may contain non-coding stretches (introns) and may therefore differ from the actual codon sequence, which is the sequence that is translated into amino acids.
  • Opsin
    An opsin is a protein which belongs to the opsin family of light-sensitive G protein-coupled receptors.
  • Optogenetics
    A method which uses light to control defined molecular events within defined cells of living organisms. It requires genetically-engineered proteins which are sensitive to light and able to switch on and off defined neurons in response to the light impulses. Optogenetics can be used to investigate the structure and function of neural networks.
  • Orthologue
    Homologous biological units (e.g., genes or proteins) are orthologues if they are found in different species and originate from the same ancestral biological unit (common ancestor). Orthologues arise through speciation from a common ancestor and have usually retained the same or similar function over the course of evolution.
  • Outgroup
    In evolutionary analysis, an outgroup is a group of organisms, taxa or other biological units (e.g., genes or proteins) which is only distantly related to the actual group of study (ingroup). Comparing traits between the outgroup and ingroup helps to determine whether the traits of interest are ancestral (present in common ancestor) or derived (not present in common ancestor) and can thus assist in creating an evolutionary tree.
  • Pairwise alignment
    Alignment of two biological sequences (nucleic acid or protein) for the purpose of comparing these sequences.
  • Paracrine signalling

    This is communication occurring between neighbouring cells. It can be through secreted chemicals or proteins.

  • Parallel evolution
    Process by which organisms, taxa, or biological units (e.g., genes or proteins) that are derived from a common ancestor have independently acquired comparable (analogous) traits. Parallel evolution can be the result of adapting to, e.g., the same ecological niche, or can be the result of other selective pressures.
  • Paralogue
    Homologous biological units (e.g., genes or proteins) are paralogues if they are found in the same species (often the same organism) and have arisen through (recent or ancient) gene duplication within this species/organism. Over time, paralogues usually become different to each other in function (and sometimes sequence).
  • Peptidyl transfer
    Peptidyl transfer is the formation of a peptide bond by covalently linking the amino acid on the growing polypeptide chain (which is attached to its tRNA bound to the peptidyl (P)-site on the ribosome) to the amino acid which is attached to its tRNA bound to the ribosomal aminoacyl (A)-site. This process is catalysed by the rRNA of the large ribosomal subunit.
  • Periaqueductal grey (PAG)
    Also called central grey. An area in the midbrain involved in the regulation of pain.
  • Phenotype
    Observable trait of an organism (e.g., morphology or behaviour).
  • Phylogenetic tree
    A phylogenetic tree (also called evolutionary tree) is a branching diagram which shows the evolutionary relationships among organisms, taxa or other biological units (e.g., genes or proteins).
  • Phylogenetics
    The study of evolutionary relationships among taxonomic groups (e.g., organisms, species and populations) or other biological units (e.g., genes and proteins).
  • Polymerase chain reaction (PCR)
    The polymerase chain reaction (PCR) technique is a technique that amplifies a piece of DNA, generating millions of copies of this particular piece of DNA.
  • Polymorphism
    When two or more clearly different phenotypes exist in the same population of a species.
  • Post-translational Modifications
    Chemical modifications that occur on proteins after they are synthesised. These modifications can alter a protein’s structure, stability, and function, and may include processes such as phosphorylation, glycosylation, acetylation, and methylation.
  • Primer (PCR)
    In the polymerase chain reaction (PCR), a primer is a single-stranded piece of DNA which serves as starting point for DNA replication. Primers have the complementary sequence to the particular sequence of DNA to be copied.
  • Primer, degenerate (PCR)
    A degenerate primer is a primers containing at least one nucleotide position which can code for more than one possible nucleotide (degenerate nucleotide). This characteristic is achieved by special, synthetic nucleotides which can pair with more than one nucleotide (e.g. A or G). The table below lists the standardised nucleotide codes for standard as well as degenerate nucleotides, and illustrates the availability of degenerate nucleotides degenerate primer synthesis. Degenerate primers are used in cases where the exact DNA sequence to be amplified is unknown or sequence variation in the sequences to be amplified might be required.
  • Proteins
    Large molecules that are made up of chains of amino acids. Proteins perform a wide range of functions in living organisms, including providing structure, catalysing chemical reactions, and transporting molecules.
  • Protein BLAST
    Protein Basic Local Alignment Search Tool is a tool which searches protein databases using a protein query. It identifies regions of local similarity between protein sequences and can thus be used to find the identity of unknown proteins in the database.
  • Protein Data Bank in Europe (PDBe)
    A database containing information on the structure of biological macromolecules.

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  • Recombinant DNA
    DNA which has been artificially engineered by recombinant technology and does not occur in such a way in nature. If the recombinant DNA is expressed, the resulting product is defined as a recombinant protein.
  • Recombinant protein
    A protein that is produced from the expression of recombinant DNA, i.e. DNA which has been artificially engineered by recombinant technology and does not occur in such a way in nature.
  • Regeneration

    This refers to the process of rebuilding damaged or old tissue by the production of new specialised cells from stem cells.

  • Reticulate evolution
    Process by which genetically distinct lineages/species recombine and a new species, which is reproductively isolated from the parent species, arises. This speciation event is called hybrid speciation. Considering reticulate evolution events when constructing a phylogenetic tree might mean that a strictly hierarchical tree structure might not be appropriate to reflect evolutionary relationships of this particular study group.
  • Residue
    A residue refers to a single unit in a polymer, such as an amino acid in a protein or a single nucleotide in a nucleic acid.
  • Ribbon diagram
    A ribbon diagram is a graphical representation of the three-dimensional structure of macromolecules. Ribbon diagrams have become a standard way of representing such three-dimensional structures.
  • Ribosome
    Molecular machine consisting of ribosomal RNA (rRNA) and proteins. The ribosome decodes the information encoded in the mRNA sequence and joins amino acids in the order specified by the mRNA. The ribosome is made of a small and a large subunit.
  • Ribosome 70S
    The 70S ribosome is the ribosome found in prokaryotes. The prokaryotic ribosome is made of a small (30S) and a large (50S) subunit. The eukaryotic ribosome is called 80S.
  • Ribosome 80S
    The 80S ribosome is the ribosome found in eukaryotes. The eukaryotic ribosome is made of a small (40S) and a large (60S) subunit. The prokaryotic ribosome is called 70S.
  • RNA
    Ribonucleic acid, a molecule that plays a crucial role in protein synthesis and gene expression. There are different types of RNA, including messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).
    SDS-Polyacrylamide Gel Electrophoresis (SDS-PAGE) is a molecular biology technique used to separate proteins in a mixture according to size by running it through a polyacrylamide matrix in the presence of the denaturing agent sodium dodecyl sulfate (SDS).
  • Self renewal

    The ability of a stem cell to divide and produce another stem cell.

  • Sequencing Chromatogram
    A sequencing chromatogram displays the data produced by the sequencing machine as a so-called trace. Each of the four nucleotides is represented by a different colour (A = green, C = blue, G = black, T = red) and the sequence can be “read” as a sequence of individual peaks. Chromatograms are stored as .abi or .ab1 files and can be viewed using specialist software (chromatogram viewers).
  • Signal peptide
    A signal peptide is a short amino acid sequence at the N-terminus of the nascent polypeptide which targets proteins to the secretory pathway (this pathway transports proteins out of the cell).
  • Signal recognition particle (SRP)
    A signal recognition particle is a protein-RNA complex which is responsible for targeting nascent proteins to the endoplasmatic reticulum (eukaryotes) or plasma membrane (prokaryotes) by binding to the protein’s signal sequence during translation.
  • Signalling molecule

    This can be a protein or chemical which can be used for communication between cells or organs in short-range or long-range interactions. An example for signalling molecules are hormones.

  • Single nucleotide polymorphism (SNP)
    A single base pair of DNA that shows variation within a population.
  • Small ribosomal subunit
    The small ribosomal subunit contains the decoding centre, which ensures that a tRNA carrying the correct amino acid according to the mRNA sequence is selected.
  • Stem cell

    A cell which can self renew and differentiate to give rise to specialised cell types.

  • Stem cell differentiation

    This is the process through which a stem cell gives rise to specialised daughter cells.

  • Stem cell niche

    The specific environment where stem cells reside.

  • Stem cell potency

    This describes the range of cell types a given stem cell can form. A newly fertilised egg cell is totipotent as it can form a whole embryo, including the placenta. Embryonic stem cells or haematopoietic stem cells are called multipotent because they can respectively form an embryo and all blood cells. Multipotent stem cells have a more restricted lineage potential, they include intermediate progenitor cells between haematopoietic stem cells and their specialised daughter cells.

  • Sticks representation (molecular structures)
    A “sticks representation” is a graphical representation of the three-dimensional structure of macromolecules. The atoms and their connecting covalent bonds are represented as lines or “sticks”. Compare to “balls and sticks representation”.
  • Synapse
    The junction of two cells which allows the transmission of a signal. Synapses usually occur between two neurons, or between a neuron and muscle or gland cell. Synapses can either be chemical or electrical and transmit signals via neurotransmitters or gap junctions, respectively. In the case of a typical neuron-neuron synapse, the signal is released from a cell’s axon terminal (signal input), ‘travels’ through the synaptic cleft, and is received from an adjacent cell’s dendrites (signal output).
  • TALENs
    Transcription activator-like effector nucleases are restriction enzymes that can be engineered to cut specific sequences of DNA.
  • Taq polymerase
    Thermostable DNA polymerase named after the thermophilic bacterium Thermus aquaticus from which it was originally isolated. It is frequently used in PCR.
  • Termination (protein synthesis)
    In the third and final phase of protein synthesis, the following happens: synthesis of polypeptide stops when the stop codon is reached; the newly synthesised protein is then released. Termination is preceded by initiation and elongation.
  • Thermocycler
    Laboratory apparatus commonly to copy DNA fragments during PCR. The cycler raises and lowers the temperature of the reaction mix in pre-programmed steps.
  • Transcription
    The process by which genetic information encoded in DNA is copied into a molecule called RNA (ribonucleic acid). Transcription is a crucial step in gene expression and allows the cell to produce different types of RNA molecules (e.g. mRNA) for various functions such as the production of proteins.
  • Transfer RNA (tRNA)
    During protein synthesis, the tRNA helps to decode the mRNA sequence into proteins. At one end, the tRNA carries a three-nucleotide sequence (anticodon) which can recognise and decode a specific codon on the mRNA. The other end of the tRNA is attached to the amino acid which corresponds to the mRNA codon. During translation, tRNAs transport the right amino acids to the ribosome, so they can be added to the growing polypeptide chain.
  • Transmembrane domain
    Three-dimensional domain of a protein which is integrated into the cell’s membrane (e.g., as part of an integral membrane protein).
  • Translation
    The process by which the genetic information carried by messenger RNA (mRNA) is used to produce the respective sequence of amino acids during protein synthesis.
  • Tripeptide
    Peptide made of three (tri) amino acids joined together by peptide bonds.
  • UCSF Chimera
    Programme for the interactive visualisation and analysis of molecular structures.
  • Uniprot
    A catalogue of protein information, including protein sequences and functions.

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  • X-ray crystallography
    A method of determining the arrangement of atoms within a crystal, in which a beam of X-rays strikes a crystal and causes the beam to spread in many specific directions. From the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density, the positions of the atoms in the crystal can be determined, as well as their chemical bonds. X-ray crystallography is used to determine the atomic structure of many materials, such as salts, minerals and metals as well as organic and biological molecules such as proteins and drugs.

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  • Zinc finger nuclease
    Artificial restriction enzymes engineered to target specific desired DNA sequences. It is most commonly used for a type of genome editing.

Topic area:  Resource collections

Age group:  16-19

Author: ELLS Team