Glossary

 

 

A : Short for adenine

ADA : Short for the enzyme Adenosine deaminase - genetic condition characterised by inability of the body to produce ADA enzyme needed for normal function of the immune system.

Adenine : One of the four bases contained in DNA.

Adenovirus : A Human virus normally responsible for respiratory infections. The modified forms of this virus are currently under testing for use as a vector for missing genes in animal models for genetic diseases.

AIDS : Short for acquired immune deficiency syndrome, a disease caused by the proliferation of HIV, in which the body’s immunological defences are destroyed, so making the sufferer susceptible to a wide range of infections.

Alanine : One of the twenty amino acids that are the constituents of proteins.

ALL : Acute lymphoplastic leukaemia; type of acute leukaemia where leukaemic cells are lymphoplasts which are the precursor of lymphocyte. Most common cancer in children.

Allele : One of several alternate forms of a gene that are present on a given chromosome. Since all mammals have two copies of each chromosome, each copy can either be identical (i.e. have the same allele) or be different in some way (different alleles on each chromosome to make the individual heterozygous.

Alzheimer’s disease : A dementia caused by a degenerative process in the brain.  Memory loss is the most obvious early symptom.

Amino acid : The building blocks of proteins.

Amniocentesis : Sampling of the fluid in the amniotic sac, the fluid that bathes the growing fetus in the uterus. In Human this is carried out between the 12th and 16th week of pregnancy by inserting a needle through the abdominal wall into the uterus.  Cells that are floating in the fluid can be isolated and used to determine the sex of the fetus and whether it is suffering from certain congenital diseases.

Anaemia : A decrease in red blood cells or in haemoglobin.

Animal model : An animal that has been induced to have a disease, which is essentially similar to one affecting Human, and can therefore be used to study possible methods of treatment.

AML : Acute myloplastic Leukaemia; leukaemic cells are myloplastic which are the Precursor of mylocyte. Most common type of acute leukaemia in adults.   

Antibiotic : Literally a substance that is antagonistic to living organisms but generally applied to substances that kill or prevent the growth of bacteria while having less effect on eukaryotes.

Antibody : Proteins produced by special blood cells, which can combat disease by recognising and binding to foreign molecules, such as those on the surface of viruses or bacteria.

Arginine : One of twenty amino acids that are the constituents of proteins.

Asparagine : One of the twenty amino acids that are the constituents of proteins.

Aspartic acid : One of the twenty amino acids that are the constituents of proteins.

Autosome : A chromosome that is not a sex chromosome.

Autosomal dominant mutation : A mutant gene situated on an autosome that is responsible for a recessive phenotype.

BAC : Bacterial Artificial Chromosome, a cloning vector used for cloning relatively large fragment of DNA in E coli .

Bacterium : A type of prokaryotic organism (simple unicellular). There are many types of bacteria, many are beneficial and few are pathogenic (causing disease).

Base : For the purpose of this book, a base is a chemical compound consisting of atoms of the element carbon, nitrogen, hydrogen and oxygen that is a component of nucleic acids.  Genetic information is encoded by the order of bases in DNA.

Base pair rule : A description of the pairing of bases in DNA. Adenine in one of the strands of DNA can only pair with and so lie opposite thymine in the other strand.  Similarly guanine can only pair with cytosine.

Bhopal : An Indian town located between Bombay and New Delhi where an insecticide factory was exploded in 3/12/1984. The people living in this town are still suffering as a consequence of this disaster.

BRCA : Short for BReast CAncer.

BSE : Bovine Spongiform encephalopathy. It is a viral disease affecting the nervous system of the cattle and hence the alternative name is mad cow disease.

C : Short for cytosine.

C. elegan : Caenorhabditis elegan belong to invertebrate, small microscopic Soil namatode used as a major model system for the study of a great variety of problems in biology and medicine. One of its significant advantages its simplicity both in anatomy and genetic organisation.  

Carcinogen : A chemical or other environmental factor (e.g. UV light) that causes cancer.

Carcinoma : A malignant and invasive tumour that is able to spread.

Cell : The basic unit of all living organisms. Some organisms such as many bacteria, consist of a single cell. Most plants and animals contain many millions of cells, of many different types, each type specialised for a particular function.

Cell culture : A method of growing cells outside the body of the organism from which they were obtained.

Cell division : The process by which cells proliferate. Cell division usually results in daughter cells, which contain genetic information, identical to one another, and to that of the mother cell from which they came.

Centromere : The dense non staining region of a chromosome that attaches it to the spindle during cell division.  

Challenger : The American space shuttle that was exploded after 73 seconds of its’ took over  and all of its’ 7 astronauts were killed instantly.

Chemotherapy : The use of chemicals to treat a disease.

Chernobyl : One of the 15 nuclear plants in Soviet Union in Pripyat town had exploded in 26/4/86 and the radiation was recorded in all Europe. more than one million people were affected by this tragedy.                   

Chorionic Villus Sampling (CVS) : A genetic testing procedure which can be done earlier than amniocentesis and in which cells are collected through a tiny tissue sample from the developing fetus. The test can reveal many but not all, genetic abnormalities.  The choice between amniocentesis and CVS is optional, as they carry minor risks and the choice to have them should be discussed with your health care provider.

Chromosome : A structure in the nucleus of eukaryote cells which contains the genetic material DNA, complexed with special proteins that allows the compact packaging of DNA.

Clone : A number of identical organisms or DNA molecules.

Coding region : The sequence of DNA in a gene that codes for the order of amino   acids in a protein.

Codon : A sequence of three adjacent bases in a DNA molecule used to determine the insertion of a specific amino acid into a protein. The dictionary of codons (which amino acid, each codon specifies) is usually called the genetic code.

COMSTECH : Organisation of Islamic Conference Standing committee on Scientific and Technological Cooperation

CJD : Creusfeldt Jakob disease, fatal slow-developing virus disease of the nervous system which result in mental deterioration and loss of co-ordination of limbs.

Cysteine : One of the twenty amino acids that are the constituents of proteins.

Cystic fibrosis : An inherited disease that affects the respiratory system, caused by an autosomal recessive mutation of the CFTR gene.

Cytosine : One of the four bases contained in DNA.

Deletion (mutation) : A change in the DNA involving the loss of one or more bases.

Developmental biology : The branch of biology which studies how complex biological structure develop from simpler ones.

Diabetes : A condition characterised by a high level of the sugar, glucose, in the blood.  In insulin-dependent diabetes, patients require a supply of insulin, usually administered by injection, to survive. Patients with insulin-dependent diabetes do not need to be administered insulin to survive.

Diphtheria : An acute contagious infection of the respiratory tract, caused by the bacterium, Corynebacterium diphtheriae. Untreated, diphtheria can lead to heart failure and sudden death.

Diffuse large B cells lymphoma : a kind of leukaemia.

DNA : Short for deoxyribonucleic acid. A macromolecule, containing the bases, adenine, cytosine, guanine and thymine, the sugar deoxyribose, phosphate, used by all organisms with the exception of some viruses, to store genetic information, which is encoded by the order of the bases in the two chains of the molecule.

DNA methylation : A process that specifically modifies DNA by the addition of methyl groups (CH3) to certain bases. DNA methylation can be used to control the use of a gene. Bacteria use modification enzymes to methylate the DNA target sequences recognised by restriction enzymes, so making these sequences resistant to cutting.

DNA polymerase : An enzyme which is a key player in the synthesis of DNA.

DOE : Department of Energy.

Dominant phenotype : A phenotype caused by the possession of a single copy of a mutant gene, i.e. the phenotype is observed even if a normal copy of the same gene is present.

Down’s syndrome : A collection of characteristics which usually includes abnormal physical and mental development.  Ninety five percent of those with Down’s syndrome have three copies of chromosome 21 (instead of two copies).

DSO : Distinguish Service Order.

Duchenne muscular dystrophy : genetic disease characterised by defective gene responsible for coding dystrophin.

Dystrophin : A protein found in muscle. Dystophin is coded for by a gene that is defective in sufferers of Duchenne muscular dystrophy.

E coli : Short for Escherichia coli.

ELSI : Ethical, Legal and Social implications.

Electrophoresis : A technique used to separate DNA molecules of different sizes, in which an electric field is applied across a gel upon which a mixture of DNA molecules has been placed.

Enzyme : A protein molecule that has a catalytic function, allowing reactions to proceed more quickly than they would otherwise.

Epilepsy : A recurrent disorder of brain functions, characterised by sudden changes of consciousness and of muscle activity.

Escherichia coli : A species of bacterium which has been and continues to be used very widely, for the study of basic biological mechanisms and for genetic engineering.

Eugenics : The ‘science’ of improving the Human race by genetic means.

Eukaryote : An organism with a cell organisation that includes the packaging of its genetic information into chromosomes within a nucleus. All plants and animals and some microbes are eukaryotes.

Fanconi’s anaemia : An autosomal recessive disorder characterised by bone marrow failure.

Fragile-X syndrome : A condition caused by the possession of an X-linked recessive mutation, which results in retarded mental development.

Foot and Mouth : It is a viral infection of Cattle, Sheep and pigs characterised by vesicular eruption of mouth and feet.

G : Short for guanine.

Gamete : The special cells, sperm and eggs, which pass on genetic information to the next generation.

GATT : General Agreement on Tariffs and Trade. An international treaty signed in 1947 to promote trade by elimination and/or reduction of tarrifs.

Gel : A jelly made with special chemicals, used for techniques such as the separation of molecules by electrophoresis.

Gene : The basic unit of genetic information. Originally defined in very general terms, it is convenient now to note that most genes contain the genetic information both to code for the assembly of amino acids in the correct order to form a protein and to regulate where, when and how much of that protein is made. The main components of a gene are the promoter and the coding region.

Genetic code : ‘The little dictionary that shows how to relate the four-letter language of nucleic acids to the twenty-letter language of the proteins.

Genetic engineering : Procedures that allow the intentional alteration of genetic information.

Genetic information : Information contained in the structure of molecules that is passed on from parent to offspring. Almost all of the genetic information of all prokaryotes and eukaryotes, as well as of many viruses, is contained in the order in which bases occur in DNA.

Genetic linkage map : A map of relative position of genes and other regions on a chromosome, determined by how often loci inherited together.

Genetic recombination : The process that brings together genetic information contained in two different organisms into a single organism.

Genetic screening : Method to determine whether an individual possesses a mutant gene, before the relevant phenotype is observable.

Genetics : The study of all aspects of inheritance.

Genome : The complete set of genetic information possessed by an organism.

Genotype : Genetic constitution of an organism.

Germ line : Those cells that have the potential to produce gametes and therefore to pass their genetic information on to the next generation.

Glutamic acid : One of the twenty amino acids that are the constituents of proteins.

Glutamine : One of the twenty amino acids that are the constituents of proteins.

Glycine : One of the twenty amino acids that are the constituents of proteins.

GM : Genetically modified; the alteration of the genetic make up of an organism.

Gonorrhoea : An acute infection of the sexual organs of Human, caused by the bacterium Neisseria gonorrhoea.

Growth factor : Small proteins that are used to pass signals from one cell type to another, often leading to changes in gene usage.

Growth hormone : A Human hormone required for normal growth and development.

Growth-promoting gene : A gene that specifies a protein that promotes cell division.

Guanine : One of the four bases contained in DNA.

Haemoglobin : The red-coloured protein contained in red blood cells that is used to transport oxygen from the lungs to the rest of the body.

Haemophilia : A condition caused by the possession of an X-linked recessive mutation, in which blood clotting is impaired, because proteins necessary for the formation of blood clots are missing. Clotting factor VIII is deficient in haemophilia A, while clotting factor IX is deficient in haemophilia B.

Helix : A linear double-stranded DNA polymer molecule is twisted to form a spiral molecule, similar to a spiral staircase. This spiral arrangement is called a helix.

Hepatitis : Inflammation of the liver that can be caused by either hepatitis viruses (e.g. type A or B) or by some drugs or excess alcohol.

Heterozygote : An individual that has two different alleles or genes encoding a protein; usually one copy is normal and the second copy encodes a non-functional or abnormal protein.

HGAC : Human Genetic Advisory Commission.

HGH : Human growth hormone produced by pituitary gland responsible for normal growth.

Histidine : One of the twenty amino acids that are the constituents of proteins.

HIV : Human immune deficiency virus, the cause of AIDS (See AIDS).

Homozygote : An individual that has two identical alleles or genes encoding a protein.

Hormone : A molecule used by the bodyto signal between different cell types.

HMS : Her/His Majesty’s Ship.

Huntington’s disease : A condition which develops in middle age of persons who possess an autosomal dominant mutation of the HD gene. Characterised by spasmodic uncontrolled movements and progressive intellectual deterioration. Also called Huntington’s chorea.

Hydrogen bond : Hydrogen bond is a type of chemical bond and is important in determining the order of the bases in the two strands of DNA pair according to the base pair rule.

Immune system : The complex system in Human that combats disease by producing antibodies.

Insertion mutation : A change in the DNA sequence resulting in the insertion of one or more bases. Transposons are a common cause of insertion mutations.

Intron : Sequences of bases, the function of which is unknown, that occur within the coding regions of most genes in eukaryotes. Introns are transcribed into RNA.

In vitro : A term that describes a reaction or process that is taking place in a laboratory using an isolated sample that has been removed from a cell or a tissue. The term is commonly used to distinguish it from a process that is being carried out inside a cell (in vivo).

In vivo : A term that describes a process or reaction that is taking place inside a cell or organism.

IQ : Short for intelligence quotient. A measure used to attempt to assess a person’s intelligence by means of a test (an IQ test).

Isoleucine : One of the twenty amino acids that are the constituents of proteins.

Junk DNA : Refer to DNA that carries no useful function -non-coding sequence.

Lambda virus  : A much-studied virus that infects the bacterium Escherichia coli.

Leucine : One of the twenty amino acids that are the constituents of proteins.

Ligase : Enzyme that is able to join together two molecules of DNA.

Linked genes : Genes which are located on the same DNA molecule (i.e. on the same chromosome) and therefore tend to be inherited together.

Lysosome : A membrane-bounded structure inside most mammalian cells that contains a collection of enzymes that are capable of degrading most types of molecules down to a smaller building blocks.

Macromolecule : Very large organic molecules, including proteins and nucleic acids.

Manic depression : A psychological state in which there is alternation between periods of extreme excitement and of depression.

Meningitis : Inflammation of the membranes enclosing the brain and spinal cord. Can be caused by either a bacterial or viral infection and can be fatal.

Metastasis : The process in which cells of a primary tumour acquire the ability to break off and form new secondary tumours in other locations.

Methionine : One of the twenty amino acids that are the constituents of proteins.

Microbe : A popular term for any small organism, that can only be seen with the aid of a microscope. Microbes, often also called micro-organisms, include bacteria, protozoa and some single-celled plants.

Microgram : A millionth of a gram.

Microlitre : A millionth of a litre.

Molecule : A basic unit of a chemical that is made up of a number of atoms of the same or different elements, for example a molecule of oxygen consists of two oxygen atoms; a molecule o urea consists of one atom of carbon, one of oxygen, two of nitrogen and four of hydrogen.

mRNA : RNA produced by transcription of the sense strand of DNA and used during the process of translation to assemble amino acids in the correct order to form proteins.

Mutagen : A substance or condition that causes mutation. Mutagens include some chemicals and UV light.

Mutant gene : A gene that has been changed as a result of mutation, resulting in a change of phenotype (e.g. in Human, red/green colour blindness, phenylketonuria).

Mutation : The process that alters genetic information. Mutation may result in the change of a single base in a gene (a point mutation) or may lead to the removal of one or many bases a deletion mutation) or may lead to the insertion of one or many bases (an insertion mutation). The term mutation is now also often used to describe the effect of mutation, i.e. a mutant gene.

Myotonic dystrophy : genetic disorder characterised by progressive wasting of muscles resulting in difficulty in walking.

NIH : National Institutes of Health.

Nucleic acid : Macromolecules originally identified because they were localised in the nuclei of eukaryote cells.

nm : Nanometre. One thousand millionth of a metre.

Nucleus : The compartment of a eukaryote cell which contains DNA.

OBE : Order of the British Empire.

Peptide bond : The bond that connect the amino acid sequence.

PCR : Polymerase chain reaction, a technique that is used to amplify DNA molecule million times quickly and cheaply.

Phenotype : The appearance of an organism. Phenotype is the result of both the genetic constitution of an organism (genotype) and of the environment in which it has developed.

Phenylalanine : One of the twenty amino acids that are the constituents of proteins.

Phenylketonuria : A condition caused by the possession of an autosomal recessive mutation of the PH gene, which results in elevated levels of the amino acid, phenylalanine. If not treated by a special diet from soon after birth, the condition can result in mental retardation.

Physical map : An overlapping collection of DNA fragments which span a particular chromosomal region, physical map may also be locations of identifiable markers spaced along the chromosomes.

Pituitary dwarfism : Abnormally short stature caused by a malfunction of the anterior pituitary gland. One of the major causes is a genetically determined deficiency in the production of growth hormone, which can now be treated by the administration of the hormone.

Plasmid : Circular DNA molecules that can exist in bacterial cells and which contain genetic information that codes for their own proliferation. Plasmids may also contain genetic information that codes for such characters as antibiotic resistance. Plasmids are widely used in genetic engineering to clone DNA from a wide variety of sources.

Point mutation : A change in the DNA sequence of a gene involving a single base.

Polio : Short name for poliomyelitis, an acute viral infection, which may result in permanent paralysis.

Polymorphism : The term refers to the variation in the sequence of a gene within a given species. Since there is a constant occurrence of mutations in the genetic information of an organism and, thus, there is a natural variation in the sequence of most genes within a population. Some of the variations result in no change in the protein sequence or result in protein sequence changes that have no impact on the function of the protein. These polymorphisms are called neutral polymorphisms or silent mutations. Other mutations can be inactivating and result in genetic defects.

Prion : Infectious protein responsible for CJD.

Positional Cloning : Identifying and cloning a gene starting from knowledge of the chromosomal map position of the gene.            

Prokaryote : An organism that does not have its DNA contained in a nucleus; bacteria are prokaryotes.

Proline : One of the twenty amino acids that are the constituents of proteins.

Promoter region : That part of the DNA sequence of a gene that is recognised by proteins that control when the coding region of the gene is to be used.

Protein : A polymer consisting of a linear string of amino acids. He order in which different amino acids occur in a proteins determines that protein’s properties. There are twenty different amino acids commonly found in proteins.

Protozoa : A group of eukaryote microbes.

Recessive phenotype : A phenotype caused by the possession of a mutant gene but which is only seen when both copies of the gene are mutant, i.e. if a normal copy of the same gene is present, the effect of the mutant gene will not be seen.

Repressor : A protein that binds to the promoter region of a gene to stop that gene being transcribed. In the presence of an appropriate signal, the repressor no longer binds and the gene can start being used.

Restriction enzyme : An enzyme that can recognise a specific sequence in a DNA molecule, called a restriction site and cut the DNA at that site.

Restriction site : A DNA sequence recognised by a restriction enzyme.

Retrovirus : A virus that contains genetic material in the form of an RNA molecule that commonly infects mammalian organisms. In Human the most characterised retrovirus is HIV, the virus that causes AIDS.

Reverse transcriptase : An enzyme that catlyses the synthesis of DNA from RNA.

Ribosome : A complex of proteins which is needed for the translation of messenger RNA into protein.

Rhino virus : A member of the group of viruses that are the cause of the common cold.

RNA : Short for ribonucleic acid. Macromolecule containing the bases, adenine, cytosine, guanine and uracil, the sugar ribose and phosphate. RNA is used by some viruses to store genetic information.  See also mRNA.

RNA polymerase : The enzyme which generates messenger RNA from the sense strand of DNA in the process called transcription.

rRNA : Structural component of the ribosome of which there are several classes. They play different roles in determining the structure and function of the ribosome. 

Seveso : A town in north Italy, evacuated in 1976 after contamination by poisonous cloud of dioxin from a factory.

Schizophrenia : A psychological condition characterised by disturbances in thought processes, feelings and behaviour.

Serine : One of the twenty amino acids that are the constituents of proteins.

Sex chromosome : A chromosome the presence of which influences the sex of an individual. The sex of a Human is determined by the X and Y sex chromosomes.  Females have two  chromosomes whereas males have an X and a Y chromosome.

X-linked inheritance : A pattern of inheritance resulting from a gene being located on the X chromosome and resulting in a different pattern of inheritance in males and females.

Sexual reproduction : Any natural process that can give rise to a Genome derived from more than one parental Genome.

Sickle-cell anaemia : Anaemia caused by having abnormal haemoglobin as a result of the possession of a mutant gene. Individuals having one mutant and one normal gene, do not have severe anaemia and are resistant to malaria.

Somatic cell : A cell that is unable to give rise to gametes and contains the total number of the chromosomes (2X).

SNP : Single Nucleotide Polymorphism, common single base-pair variations in DNA.

Splicing : A technical term used for the joining together of two parts of a messenger RNA molecule, after the removal of an intron.

Spontaneous mutation : A mutation that occurs without the action of a mutagen.

Stem cells : An unspecialised cell type that can continue dividing indefinitely, generating daughter cells that can differentiate into various cell types.

Sticky end : A colloquial term used to describe the single stranded end of a DNA molecule generated by cutting with a restriction enzyme. The ends are called sticky because the single stranded region can repair with the single stranded region of another sticky end generated by the same restriction enzyme.

Syphilis : A contagious disease, caused by the bacterium Treponema pallidum, normally transmitted by sexual contact. Untreated, can cause dementia.

T : Short for thymine.

Tay Sachs : fatal neurological disease of early childhood characterised by seizures and paralysis.

Terminator Gene : A gene that act as a signal for termination of the transcrition. It is the inserting of this gene to the already transformed plants to kill the seeds just as they are completing their development on the parent plant. The reason for doing this is to prevent farmers who have bought the seeds of transformed crops from producing successive generations for their own use circumventing the need for further purchase of seed.

Thalassaemia : Anaemia caused by having abnormal haemoglobin as a result of the possession of a mutant gene. Individuals having one mutant and one normal gene, do not have severe anaemia and are resistant to malaria.

Three Mile Island : An American place in Pennsylvania where an accidents happened in nuclear power plant resulted in the release of radioactive materials in 1979. More than 140.000 of its’ inhabitants were evacuated.

Threonline : One of the twenty amino acids that are the constituents of proteins.

Transcription : The process, catalysed by RNA polymerase, that produces messenger RNA from the sense strand of DNA.

Transformation : A method of sexual reproduction in which an organism receives genetic information in the form of pieces of DNA and uses this to modify its Genome.

Translation : The process in which genetic information coded in the sequence of bases in a messenger RNA molecule is used to specify the order into which amino acids are joined together to form a protein.

Transposon : A sequence of DNA that has the property of being able to move from one position in a Genome to another.

tRNA : The RNA molecule that provides specificity to the translation process. tRNA carries specific anticodon which is complementary to the codon on the mRNA and result in an amino acid being placed in the lengthening molecule.   

Tryptophan : One of the twenty amino acids that are the constituents of proteins.

Tumour : A clump of cells produced as a result of the loss of the normal mechanisms controlling cell division.

Tuskegee : Is a town in Alabama in the United States where an experiment were conducted in 1932 on black people who had syphilis. Those people had neither been told about the disease nor had been given the antibiotics for treatment. The US Public Health services withheld treatment from 399 black person from 1932-1072 to study how Syphilis spread and how it killed. Only 8 persons survived this tragic and inhuman incident.

Tyrosine : One of the twenty amino acids that are the constituents of proteins.

U : Short for uracil.

Uracil : A base contained in RNA but not in DNA. Uracil replaces thymine in RNA, which does not contain thymine.

Valine : One of the twenty amino acids that are the constituents of proteins.

Vector : Used in genetic engineering to describe a DNA molecule, usually derived from a virus or a plasmid, which can be used for cloning DNA.

Virus : microorganism composed of proteins and nucleic acid, that can only grow and divide within a living cell. The nucleic acid can be either DNA or RNA.

X-linked recessive mutation : A mutant gene located on the X chromosome, that in females is recessive, i.e. both copies of the gene must be mutant for the phenotype to be affected (males only have one X chromosome and so will be affected if this contains the mutant gene).

Zygote : The single cell formed as a result of the fusion of two gametes (e.g. egg and sperm) in sexual reproduction.