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module:DNA: Structure and function


acid group  
Phosphoric acid is part of nucleotides, and therefore part of DNA and RNA, the 'A' in both terms stands for 'acid'
adenine, A  
DNA and RNA base, pairs with thymine (T) in DNA or uracil (U) in RNA.
amino acid  
Building blocks of proteins, there are about 20 different amino acids.
A serious infection caused by the bacterium Bacillus anthracis, possible candidate for biological warfare
Complex protein which is capable of recognising and eliminating foreign particles in the body, such as bacteria and viruses.
asexual reproduction  
Cloning, the creation of an exact copy of an existing organism. Also happens in nature. Bacteria reproduce in this way as do many plants e.g. strawberry 'runners' are all clones of the parent plant. Identical twins are also clones.
Simple, single-celled organism responsible for some diseases (e.g. anthrax) but very important in decay processes. DNA of bacteria is very easily extracted and modified
base pairs  
The 'rungs' of the twisted ladder that is DNA. Only certain combinations of bases can form complete chemical 'rungs' producing the so-called 'base pairing rule'
An ecological term reflecting the degree of genetic variability in an ecosystem. Generally, the larger the biodiversity the greater the ecosytem's ability to respond to change, due to the richness of genetic potential within it.
The exploitation of biological processes for industrial, research or environmental purposes. This includes genetic engineering, and also brewing, baking, sewage treatment and biological washing powders, amongst many others.
Bovine Spongiform Encephalopathy or 'mad cow disease'
Disease caused by uncontrolled cell division, producing a mass of functionless cells which invade and destroy normal organs (a tumour). Invariably caused by critical mutations (changes) to DNA responsible for controlling cell growth.
Cancer-promoting chemicals.
The basic unit of all living things, including plants, animals, fungi and bacteria. Viruses and prions are the only biological particles that do not possess cells.
A threadlike "package" or structure of genes, made up of DNA in the nucleus of a cell. Chromosomes direct the activity within the cell and pass on genetic information to new cells. Different kinds of organisms have different numbers of chromosomes. Humans have 23 pairs, 46 in all: 44 autosomes and two sex chromosomes.
Creutzfeldt-Jakob Disease, new variants of this are likely to be identical to BSE
An individual produced by asexual reproduction. Although common in many living things, cloning is rare in animals and very rare in higher species. Identical twins are the only natural clones in mammals, producing clones in any other way is a technically complex process, with very low success rates. Potentially, clones could be very useful in agriculture e.g. the cloning of a prize dairy cow, but is fraught with ethical concerns when applied to humans, where practical applications are rather more limited.
cylosine, C  
DNA and RNA base, always pairs with guanine (G)
cystic fibrosis  
Genetic disease in which the body produces abnormally thick mucus, producing symptoms in the intestines (poor digestion), lungs (infections and wheeziness) etc.
5 carbon sugar within the DNA molecule (D of DNA stands for deoxyribose)
deoxyribonucleic acid  
Stable polymer which forms a double helix structure, rather like a twisted ladder. DNA is the molecule that carries inherited features from generation to generation and controls the activities of cells. See also DNA
Hormonal disease in which blood sugar is abnormally high, caused by lack of the hormone insulin or apparent insensitivity to its effects (insulin normally lowers blood sugar).
DNA is the molecule that carries inherited features from generation to generation and controls the activities of cells. See also deoxyribonucleic acid.
DNA ligase  
Enzyme which can join together two strands of DNA 'end-to-end' producing a new gene. Acts rather like DNA 'glue'
dominant gene(s)  
Dominant genes require only a single line of inheritance to cause symptoms
double helix, double helices  
The final appearance of the DNA molecule produced by two sugar phosphate backbones twisting around each other, the space between them being filled with pairs of bases joined by hydrogen bonds.
environmental stress  
Any outside factor which influences the expression of genes e.g. In very simple terms, a gene for dark skin will only be fully expressed if you are exposed to enough sunlight.
Proteins which speed up biochemical reactions. Without enzymes life processes would be very slow!
The theory that all living things have been produced from simpler, more primitive ones by a series of gradual changes brought about by chance over immense periods of time.
Sex cells e.g. sperm or eggs. These always contain half the normal amount of DNA and also contain a random assortment of the 'parent' DNA.
Length of DNA (genetic code) which codes for a single protein molecule.
gene therapy  
An approach to treating genetic diseases which involves replacing mutated genes with normal ones. For example, cystic fibrosis sufferers can inhale viruses or tiny droplets containing 'normal' genes which can become incorporated into their lungs.
Pertaining to genes or DNA, for example genetic disease, genetic engineering
genetic code  
The sequence of bases along a sugar phosphate backbone, when read in three letter 'words' (e.g. TTA, AGC etc.). This, in turn, encodes the structure of a particular protein
genetic engineering  
The use of modern techniques to 'cut' and 'stick' DNA into the genome of an organism, enabling it to express new characteristics e.g. pest resistance in crop plants.
genetic fingerprint  
A technique which exploits the fact that everyone has different DNA (apart from identical twins) to produce a unique profile, appearing rather like a bar code, from which individuals can be identified.
genetic material  
A reference to DNA in bulk, such as that from a blood sample or similar.
genetic modification  
Genetic engineering
genetic recombination  
The random 'mixing' of genes, both within individuals as gametes (sex cells) are formed, and between individuals when these gametes combine to produce a new individual
genetically inherited diseases  
Congenital diseases caused by the sufferer inheriting one or more copies of a defective (mutant) gene
All of the DNA in a normal cell from a particular species. In humans, the genome refers to all the DNA contained within the 46 chromosomes found in normal cells
The composition of a person's DNA with respect to a particular characteristic e.g. eye colour. This may include 'hidden' recessive genes that the person does not express.
germline therapy  
An approach to gene therapy, currently illegal. Germline therapy involves inserting a 'normal' gene into an embryo which is carrying a genetic disease while it is still composed of only a few cells. This essentially 'cures' the disease at source and the resulting individual will never suffer the disease. Banned because the human genome is irretrievably altered, not only for the individuals concerned but all of their children, grandchildren etc.
Genetically Modified
GM food  
Genetically Modified food. Foodstuff containing ingredients from genetically modified organisms (usually crop plants).
GMOs, genetically-modified organisms  
Any living thing subjected to genetic modification/engineering
guanine, G  
DNA and RNA base, always pairs with cytosine - C
The protein which fills red blood cells, giving them, and blood, their characteristic red colour. Essential in carrying oxygen to the body.
Chemical messengers released into the blood to produce a response elsewhere e.g. adrenaline
Human Genome Project  
The completed project to 'read' the genetic code of all the DNA contained within the human genome
Huntingdon's chorea  
Genetic disease in which degeneration of the nervous system produces gradually worsening paralysis and eventual death, usually in middle age.
hydrogen bond  
Weak chemical bonds between bases in DNA, the pairs of bases form the 'rungs' of the twisted ladder of DNA and are kept in place by hydrogen bonds.
The process by which features are passed on from parent to child, DNA is the molecule that is the inherited material.
Natural hormone which lowers blood sugar, can also be synthesised in genetically engineered bacteria and used to treat diabetics who lack the hormone.
Infectious disease common in the tropics, transmitted by mosquitoes. Causes recurrent bouts of fever and can cause anaemia and fatal convulsions.
mitochondrial DNA  
Mitochondrial DNA (mtDNA) is found in cell mitochondria - tiny structures in a cell, outside the nucleus that help produce cell energy. Unlike nuclear DNA, mitochondrial DNA is only passed on through the egg - some traits are inherited only through the maternal line.
The smallest particle of any pure substance produced from the combination of basic elements (e.g. carbon, oxygen).
Change, usually to DNA. Generally human mutations are damaging, even fatal. Occasionally they are beneficial and contribute to evolution
nervous system  
Brain, spinal cord and peripheral nerves connected to sense organs, muscles and glands.
nuclear DNA  
Nuclear DNA is found in the 46 chromosomes within the cell nucleus. 23 chromosomes come from the mother's egg, the other half from the father's sperm.
Pertaining to the nucleus, the 'heart' of the cell. The nucleus not only contains most of the DNA of a cell, but also RNA and protein in large amounts
The building blocks of DNA and RNA, which are both polynucleotides (polymers of nucleotides). Each nucleotide, in turn, is made up of a 5 carbon sugar (deoxyribose in DNA, ribose in RNA), a phosphoric acid and an organic base (adenine, thymine, cytosine or guanine in DNA; adenine, uracil, cytosine or guanine in RNA)
nucleotide base(s)  
The crucial component of a nucleotide, and therefore of DNA or RNA. The base sequence along either molecule is the genetic code.
The 'heart' of a cell, containing DNA, but also RNA and protein.
Living thing.
phenotypic genes  
Genes which are apparent or expressed in the person carrying them. Essentially, phenotype = genotype + environment.
pipette, pipetting  
Accurate transfer of volumes of liquid
Small loop of DNA which bacteria can transfer to one another, thereby taking on new characteristics e.g. antibiotic resistance. Can also be exploited by genetic engineers who use plasmids to 'deliver' new genes into bacteria for their own purposes.
Infectious protein which has the remarkable property of causing other, normal proteins to change shape and become infectious. Responsible for BSE, CJD and other rare brain diseases.
Long-chained molecules used to build and repair cells, made of one or more chains of amino acids
protein synthesis  
The production of proteins using RNA molecules as a 'template', this RNA being, in turn, produced from an original DNA code (a gene)
recessive gene(s)  
Recessive genes require two mutant genes - one from each parent - to cause symptoms
Copy. DNA has the remarkable ability to produce identical copies of itself, a by-product of the strict 'base pairing rule'
restriction enzyme technique  
Restriction enzymes are capable of cutting the sugar-phosphate backbone of DNA, producing two or more fragments. Essentially, DNA 'scissors'
A five-carbon sugar within the RNA molecule (R of RNA stands for ribose)
Tiny particles in cells which assemble proteins from amino acids by reading RNA 'templates'
RNA (ribonucleic acid)  
Long molecule that reads the genetic code carried by DNA, consisting of information needed to build proteins.
sickle cell anaemia  
Genetic disease in which red blood cells collapse during exercise or at high altitude producing pain, anaemia, stroke or heart attack
somatic therapy  
The current approach to gene therapy. 'Normal' genes are delivered in some way to the body (somatic) cells of sufferers from genetic diseases, helping to relieve the symptoms. However, this approach will not 'cure' the disease as these somatic cells will not live forever and when they die, mutated cells will replace them, meaning the treatment must be repeated. Also, the sufferer will still be capable of transmitting the disease to their children.
sugar phosphate backbone  
The strong 'thread' which holds DNA or RNA molecules together. Made of alternating sugar and phosphoric acid components of the component nucleotides
synthesis, synthesise  
Create or produce
Tranquilizer drug, notorious for its ability to produce limb deformities in the children of mothers who consumed it during pregnancy.
thymine, T  
DNA base, always pairs with adenine (A)
uracil, U  
RNA base, always pairs with adenine (A)
A means of preventing infectious diseases by exposing the immune system to a 'safe' version of the causative bacterium or virus. This stimulates the immune system to produce appropriate antibodies, which protect the person vaccinated from the actual infection. e.g. measles, small pox etc.
Non-cellular infectious particles composed of a protein coat and DNA or RNA genome. Cause diseases such as AIDS, common cold, measles
vitamin A  
Naturally occurring vitamin which is necessary for the formation of epithelia (linings and coverings of the body e.g. skin) and a light sensitive chemical in the eye responsible for vision in dim light. Vitamin A deficiency is therfore associated with scarring of the skin and other epithelia, particularly the covering of the eye (cornea) and 'night blindness'.

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