Topic 6- Glossary Flashcards
Fingerprints
The pattern of skin folding on the fingers of humans (and some other animals) – each person’s pattern is unique.
DNA fingerprinting or DNA profiling
A technique to identify individuals; relies on differences in the number of times a mini- or micro- satellite sequence is repeated on each chromosome. At least 10 or more microsatellite sequences are used to produce a unique profile for each individual with the exception of identical twins.
Dental records
*Records of these can be used to identify bodies that are damaged, as they are very slow to decay, and more resistant to burning.
Introns
Non-coding bocks of DNA, or intragenic regions.
Exons
Coding regions of DNA, or expressed regions.
Short tandem repeats
Another term for satellites- DNA sequences within introns repeated many times. Also known as mini or micro-satellites.
Restriction enzyme
Or restriction endonuclease
An enzyme produced by bacteria that can cut DNA molecules at specific sites.
Recognition site
The sequence of nucleotides in DNA to which a restriction enzyme binds and then cuts the DNA.
Agarose gel electrophoresis
Use of an agarose gel matrix placed in salt buffer in which molecules of DNA can be separated on the basis of size, when a current is passed through the gel.
Southern blotting
The process by which DNA fragments are transferred from the agarose gel to a nylon or nitrocellulose membrane.
Nylon or nitrocellulose membrane
A charged membrane that provides a solid support to which DNA separated by gel electrophoresis can be transferred. Used to allow subsequent manipulations of the DNA.
Agarose
A substance that when heated with buffer and cooled forms a gel.
Hybridisation
The process where two complementary DNA strands will anneal (bond together) by hydrogen bonding
X-ray film
Light or radioactive sensitive film.
Labelled DNA probe/gene probe
A short single stranded length of DNA, that is complementary to a target gene sequence that has attached to it a fluorescent or radioactive marker.
Polymerase chain reaction
A technique that allows the automated replication of a particular stretch of DNA using a thermostable DNA polymerase. Involves several rounds of denaturation, annealing of primers to the template strand, and polymerase extension from the primers. It will result on many identical copies of the target sequence.
DNA polymerase
An enzyme which catalyses the joining together of individual nucleotides to form a molecule of DNA.
Primers
Short single stranded sections of DNA used in the above procedure, which are complementary to the sequence either side of the target sequence. They are marked with a fluorescent tag.
Amelogenin (amg) gene
Gene found on the X and Y chromosome, which codes for a protein found in tooth enamel. The alleles on the X and Y chromosome are different lengths and provides a method for determining gender on a DNA profile. PCR of this gene will produce 1 band on a gel if female and 2 bands if male.
Core temperature
Internal body temperature – 36.2 - 37.6C
Sigmoid curve
Cooling of the body follows a __________ __________
Rigor mortis
The stiffening of muscles after death due to lack of ATP in muscle cells
ATP
Adenosine triphosphate. The common “energy currency” of all cells.
Lactic acid
Chemical formed by anaerobic respiration in animal cells, which causes the pH to drop, inhibiting further enzyme reactions.
Decomposition
Also known as putrefaction; the break-down of body tissue to simpler molecules.
Autolysis
Early stage of decomposition involving the body’s own enzymes from the digestive tract and lysosomes.
Bacteria
Enzymes will also be released from these organisms, resulting in further decomposition and gas formation.
Greenish decolourisation
One of the first signs of decomposition
Hydrogen sulphide, methane, carbon dioxide ammonia and hydrogen
Bloating of the body due to these gases building up in the gut and tissues
36-72 hours after death
Time taken for discolouration of abdominal wall to occur
1 week, 3 days if temperature 26-30 C
after death
Time taken for gas formation to occur
Forensic entomology
The application of knowledge about insect lifecycles to estimate time of death.
Larva
The pre-adult form of fly that hatches from an egg, also called a maggot.
Instar
An immature stage of an insect between successive molts.
Pupa
Stage between larva and adult of some insects during which metamorphosis occurs.
Calliphora vicina,
Most common blue bottle (or blowfly) found on bodies
Cocaine
An example of a drug that can affect the rate of maggot development.
Succession
In entomology, the gradual sequential series of changes in species of insect found in a decomposing body. Note, unlike with the comparable situation with plants, most of the early insects will still remain on the body.
Decomposers
The bacteria and fungi essential in sustaining the carbon cycle are also known as these.
Post mortem
The examination of a dead body to ascertain cause of death.
Tuberculosis
A contagious disease principally affecting the lungs, caused by the bacterium Mycobacterium tuberculosis
Human immunodeficiency virus (HIV)
A human retrovirus which that infects T helper cells and so disables the immune system, leading to AIDS.
AIDS
The result of infection by HIV, where the immuno-compromised person is susceptible to opportunistic infections.
Peptidoglycan
A polysaccharide, cross-linked by peptide chains, and the major constituent of the bacterial cell wall.
Gram positive bacteria
These bacteria have walls that are thickened with additional polysaccharides and proteins.
Gram negative bacteria
These bacteria have thinner walls, but also have a surface layer of lipids for protection.
Pilus (plural pili)
Protein tubes that allow bacterial attachment to surfaces and cells.
Mesosome
Infolding of the bacterial cell surface membrane and the site of respiration.
Capsule
Mucus layer surrounding the cell wall of the bacteria providing protection and preventing dehydration; it also allows bacteria to form colonies. Only present in some bacteria, e.g. TB
Flagellum
Used for cell movement.
Plasmid
Small circles of DNA found in some but not all bacteria, in addition to the main loop of genomic DNA.
Glycoprotein
Compound of protein and polysaccharide.
Host
Organism supporting a parasite (e.g. a virus), in or on its body to its own detriment. (Can also be used to describe an organism supporting a commensal organism.)
Lysis
Destruction of cells through damage of the plasma membrane.
icosahedral
Viruses come in a wide variety of shapes and sizes; a spherical virus is also described as _____________
Tobacco mosaic virus
First virus discovered. A rod shaped plant virus.
Bacteriophage
A virus that infects bacteria.
Pathogen
A disease causing parasite, usually a microorganism.
Droplet infection
Infection by inhalation of droplets of mucous and saliva containing the infectious organism.
Body fluids
HIV is carried in some of these, e.g. blood, vaginal secretions, and semen, (but NOT saliva or urine).
Sexually transmitted infection
Any diseases transmitted through (unprotected) sexual contact.
Maternal transmission
Transfer of HIV from mother to unborn child or infant.
Immune response
Mechanisms mounted by the immune system to attempt to destroy an invading pathogen.
Antigen
Any large molecule that triggers an immune response by lymphocytes. These are usually proteins, but may be other types of molecule such as polysaccharides, or lipids.
Antibodies secreted by lymphocytes will bind (specifically) to these molecules.
Lysozyme
Enzyme found in tears, saliva and nasal secretions, that kills bacteria by breaking down their cell walls
Inflammation
A non-specific response to infection which results in redness, oedema, pain and an increase in temperature. Due to the release of histamine from damaged white blood cells and mast cell.
Mast cells
Cells found in connective tissue below the skin and around blood vessels, which release histamine (along with damaged white blood cells) in response to cell damage.
Histamine
A chemical released by white blood cells and damaged mast cells. Responsible for the increase in capillary permeability resulting in oedema, and dilation of capillaries resulting in reddening of the area from increased blood flow.
Oedema
Swelling of an area due to excess tissue fluid accumulation
Phagocytes
A white blood cell that engulfs microorganisms and other foreign matter by endocytosis
Neutrophils
Majority of white blood cells that destroy bacteria. Leave the blood capillaries by squeezing between the cells of capillary walls. Short lived.
Macrophages
A type of white blood cell that develops from monocytes that also leaves the blood capillaries by squeezing between the cells of capillary walls to engulf and destroy bacteria, foreign matter and cell debris.
Phagocytosis
A form of endocytosis, where the white blood cells engulf and then digest the bacteria.
Platelets
Fragments of cells important in the blood clotting process
Pus
Thick fluid that forms in an infected area consisting of dead cells, mostly neutrophils.
Lymph nodes
Specialised lymphoid tissue regions that act as filters for microorganisms and contain lymphocytes and macrophages.
Lymph
A clear watery fluid that contains lymphocytes. There is a series of vessels that run throughout the body, collecting excess tissue fluid and returning it to the bloodstream
Lymphocytes
White blood cells that help to defend the body against specific diseases. Two types: T and B cells.
Septic shock
Widespread infection or “blood poisoning”
Interferon
Non-specific defence chemical produced by virus infected cells, it diffuses to the surrounding cells where it can prevent viruses from multiplying, by inhibiting viral protein synthesis.
B cells
Lymphocytes that are produced in the bone marrow, which develop into a plasma cell and secretes antibodies in response to antigens.
T cells
Lymphocyte, produced in the bone marrow and matured in the thymus gland. Two type: T helper and T killer cells.
Specific immune response
Response by lymphocytes to specific disease microbes
Immunoglobins or antibodies
A class of proteins secreted by B cells, that can bind antigens. They consist of four polypetide chains held together by disulphide bonds forming a characteristic Y shape.
Antigen binding site
The variable part of the antibody that can bind specifically to on type of antigen as the shape of the antibody and antigen are complementary.
Constant region
The region of an antibody that shows little variation between different types of antibodies.
Clonal selection
The process where B- cells (and T cells) divide to produce two clones of the original cell that has bound to the antigen.
Plasma cells
An antibody-secreting cell that differentiated from a B effector cell.
B memory cells
Long-lived B cells produced from clonal selection following antigen recognition, important in immunity.
Primary immune response
The first time that B cells are selected by the antigen and plasma cells produced (10 to 17 days)
Secondary immune response
The second time a person is infected, the memory cells divide to produce plasma cells within 2 to 7 days. More antibodies are produced and the response lasts longer. The person is said to be immune.
Bone marrow
The bone tissue which forms the blood cells.
Thymus gland
Located within the thorax. A portion of the lymphoid system in which T cells mature and differentiate after they have migrated form the bone marrow where they were produced.
Cytokines
Proteins produced by activated T cells that stimulate division and differentiation of B cells.
CD4 receptors
Receptor on the surface of T cells which binds to the antigen/MHC complex on the surface of antigen presenting cells. (CD = cluster of differentiation proteins). HIV has evolved to use this receptor to allow entry into the T helper cells.
T killer cells
T-cells which destroy pathogen infected cells by releasing chemicals that caused pores to form in the infected cells causing lysis. They can also attack other foreign cells that enter the body.
T helper cells
T-cells which produced cytokines which stimulate B-cells to become plasma cells and to enhance the activity of phagocytes, and stimulate the T killer cells to divide.
Antigen presenting cell (APC)
A cell that displays an antigen on its surface in conjunction with MHCs (major histocompatibility complex).
Lock and key mechanism
Mechanism proposed for binding of enzyme to substrate due to the active site of the enzyme having a complementary shape and charge to the substrate.
Auto-immune diseases
Diseases caused where body tissues are targeted by inappropriate action of the immune system. Examples of such diseases include rheumatoid arthritis, multiple sclerosis and type I diabetes.
Apoptosis
The process by which cells are “programmed” to die, also known as programmed cell death. This is distinct from cell death due to infection or damage.
Primary infection
First phase of TB lasting for several months with possibly no symptoms.
Obligate aerobes
Organisms which require oxygen to survive.
M. tuberculosis bacteria can survive inside macrophages because they have _______________________________
Thick waxy cell walls
Dormant
Describes the state where the M. tuberculosis remain alive but inactive (very low metabolic activity) for many years.
M. tuberculosis can also ____________ T cells. This reduces antibody production and attack by T killer cells.
suppress
Active tuberculosis
Second phase of TB, this occurs if the patients immune system was unable to contain the primary infection, or if an old infection breaks out if the patient becomes immuno-compromised.
Hypothalamus
A part of the brain which lies below the thalamus and contains the thermoregulatory centre. It coordinates water balance, reproduction, metabolism as well as temperature.
Homeostasis
Mechanisms, which maintain a relatively constant internal body environment.
Set point
Also known as norm value, the condition at which homeostasis mechanisms will maintain the body.
Denature
Loss of activity of an enzyme because of a change in enzyme structure due to heat, pH changes or other means.
(Term can also refer to the separation of two DNA strands when heated)
Glandular TB
Main symptoms include enlarged lymph glands due to infection with TB. More common in Asian people.
Enveloped virus
Lipid membrane surrounding some viruses which is derived from the host cell membrane
gp120
Glycoprotein, which projects through the viral envelope, important for HIV virus binding to the host cell.
Reverse transcriptase
Enzyme which uses viral RNA as a template to form a complementary strand of DNA
Integrase
Enzyme which inserts viral DNA into host DNA.
Triplet code
The genetic code is this type of code, whereby 3 bases code for one amino acid
On the DNA strand a group of three bases that codes for one amino acid is known as the triplet code. The sequence of three nucleotide bases on a messenger RNA molecule that codes for a particular amino acid is known as a __________
codon
mRNA
This molecule carries information from DNA in the nucleus to the cytoplasm for protein transcription. Genes are sections of DNA which code for particular proteins. DNA is too large to pass through the nuclear pore, so this molecule takes a copy of the genetic code into the cytoplasm, where it enables amino acids to be assembled in the correct sequence to make a protein.
transfer RNA (tRNA)
A molecule of RNA which folded to form a shape resembling a t; it has an amino acid binding site at one end and a specific anticodon at the other.
ribosomal RNA (rRNA)
This is a type of RNA which is found in ribosomes – a complex structure of RNA and protein.
Transcription
The synthesis of RNA using one strand of DNA as the template. The mRNA molecule leaves the nucleus to be translated.
RNA polymerase
Enzyme which catalyses the polymerisation of RNA nucleotides in a 5’ to 3’ direction to form RNA
Promoter
Links to Topic 3 and 7. The sequence of bases just prior to the gene where RNA polymerase binds to start transcription.
Transcription factors
Links to Topic 3 and 7. The additional proteins that form a complex with RNA polymerase and the promoter, without which transcription could not start.
Transcription initiation factors
The complex formed when RNA polymerase and transcription factors bind to the promoter and transcription is initiated.
Template strand
Antisense strand, strand of DNA used to produce mRNA
Coding strand
Sense strand of DNA.
mRNA splicing
The process between transcription and translation, where the non-coding introns on the mRNA strand are removed, and the coding regions rejoined, prior to translation. Different proteins can be formed from one RNA depending on how the coding sequences are rejoined
Translation
A process which takes place on a ribosome, where amino acids are joined to form a polypeptide. The mRNA produced during transcription leaves the nucleus and becomes attached to the ribosome where this process takes place; tRNA molecules collect the appropriate amino acid from the cytoplasm and bring it to the ribosome where the protein is being synthesised.
Ribosomes
Sometimes free in the cytoplasm, sometimes linked to endoplasmic reticulum. A small organelle made of RNA and protein found either free in the cytoplasm or attached to the membranes of the rough endoplasmic reticulum. Protein synthesis takes place on ribosomes.
Anticodon
A sequence of three nucleotide bases on a transfer RNA molecule, which is complementary to the corresponding messenger RNA codon.
Acute phase
Early infection with HIV. Phase of rapid replication of virus and loss of T helper cells. HIV antibodies appear in the blood after 3-12 weeks.
Chronic phase
Prolonged stage of HIV infection, where the virus continues to reproduce rapidly, but the numbers are kept in check by the immune system.
Disease phase
Phase associated with a high HIV viral load, a declining T helper cell count and subsequently the onset of AIDS
Opportunistic infections
Organisms that less commonly cause disease in people with functional immune systems, but which can invade those who are immuno-compromised, usually when the T helper cell count drops below 200 per mm3 of blood.
Kaposi’s sarcoma
A tumour (obvious purple black patches) frequently found in AIDS patients, but rare in the general population.
Physical barriers
Barriers to prevent pathogen entry e.g. the skin
Chemical defenses
Non-specific chemicals produced by the body, which help to prevent pathogen entry.
Skin flora
Microbes that live on the skin, not usually causing any disease. Act to prevent colonisation by other bacteria, as they are well adapted to the conditions on the skin and out compete other microbes.
Mucus
A slimy viscous fluid secreted by specialised cells.
Cilia
Hair-like projections from a cell, which beat in a co-ordinated rhythm, commonly move fluids or mucous.
Stomach acid
Produced to aid digestion, but also kills bacteria that enter with food
Passive natural immunity
Short term immunity produced when antibodies are passed from mother to foetus via the placenta and to her infant through her milk. Antibodies are not produced by the foetus/infant.
Active natural immunity
Immunity produced by the specific immune response to an infectious organism. The infected person produces antibodies.
Active artificial immunity
Immunity produced in response to vaccination. The vaccinated person produces antibodies.
Passive artificial immunity
Short term immunity produced by injection of antibodies. Antibodies are not produced by the person.
Vaccine
The use of a pathogen antigen to bring about an immune response. Whole, attenuated or killed, microorganisms can be used, or just a part of the pathogen. A harmless version of a bacterial toxin can also be used.
Attenuated
Pathogen which has been weakened in some way so that they no longer produce disease.
Herd immunity
When a significant proportion (will vary according to the disease) of the population are immunised, the rest of the population are less likely to contract the disease.
BCG vaccine
Bacille Calmette Guerin
Vaccine to protect against TB; used to be given to young people between the ages of 10 to 13 years. Contains chemically attenuated bacteria. Only given now to selected people.
Reverse transcriptase inhibitors
Drug which prevents the HIV viral RNA from making DNA
Protease inhibitors
Drug which prevents the cutting of large proteins into small polypeptides
Antibiotics
A chemical substance, produced by microorganisms, which has the capacity to inhibit growth or destroy bacteria in dilute solutions.
Alexander Fleming
Research scientist who discovered Penicillin
Penicillin
An antibiotic that inhibits bacterial cell wall synthesis. Affects many bacteria e.g. pneumonia, scarlet fever, but not TB
Waksman and Schatz
Co-discoverers of streptomycin, found by testing many soil organisms for antibacterial activity.
Streptomycin
First drug found that could cure tuberculosis.
Bactericidal
A substance which destroys bacteria
Bacteriostatic
A substance which stops the bacteria from multiplying
Antibiotic resistance
The ability of the bacteria to survive in the presence of the antibiotic, due to a mutation.
Selection pressure
An environmental factor that, when present, is a survival or reproductive disadvantage to a proportion of a population.
Evolutionary race
Pathogen and host will always be co-evolving in an ___________ _________: the pathogens, which are best able to grow and multiply, will be selected for, and the hosts, which are most resistant to pathogens, and therefore more likely to survive, will be selected for.
Plasmid
A circular piece of DNA, distinct from the bacterial genomic DNA. Is replicated along with the chromosomal DNA.
Conjugation
A process that occurs in bacteria in which DNA (usually a plasmid) is passed from one cell to another, usually through the pilus.
Multiple resistant strains
Bacteria which have evolved resistance to several antibiotics
MRSA
Staphylococcus aureus which is resistant to most antibiotics including methicillin.
HCAIs
Healthcare associated infections
