Topic 6 Flashcards
What does DNA profiling rely on
The fact that everyone’s DNA bar twins is unique
What are introns
They are non-coding blocks and are inherited in the same way as genes
What do introns contain
They contain STR satellites that are repeated several times
Although the same str occur at the same loci on both chromosomes of a homologous pair how do they differ
They differ in the number of times they are repeated
Why is the variation in the number of repeats of str on a loci good
Scientists use this to create unique DNA profiles
Gives the steps in obtaining a Tissue sample
A sample of DNA is collected from biological tissue i.e. Blood smear
The tissue sample is broken using a buffet solution that contains a salt and detergent the cell memebranes are disrupted
The DNA is separated from the rear of the cell debris by flirtation and centrifuging
Proteins are removed due the fact that protease enzymes are incubated and cold ethanol is used to precipitate the DNA
What two ways can be used in creating DNA fragments
Restriction enzymes or Polymerase chain reaction
Where do restriction enzymes come from
They are found in bacteria and its name is reflected by the bacteria it comes from
What do restriction enzymes do
They cut DNA at specific recognition sites at either side of the DNA which means the fragment is intact but cut from the rest of the genome
When do restriction enzymes cut a DNA sample
When their specific restriction sequence occurs
What are DNA primers
They are DNA sequences that contain fluorescent tags and are complementary to the DNA adjacent to the str
Describe the steps of PCR
A the DNA from a sample along with DNA polymerase, DNA primers with markers and nucleotides are added to a reaction tube
At 95 degrees the DNA separates into two strands
At 55 the DNA primers attach to the start of the str repeated sequence on each strand
At 70 DNA polymerase attach the two nucleotides together which extends the extend the DNA from the primer and the str repeated sequence along with the DNA adjacent are replicated DNA polymerase is attached
This cycle repeats its self producing a large number of DNA fragments
What method is used to separate the DNA fragments
Gel electrophoresis or southern blotting
What technique is used to separate DNA fragments
Gel electrophoresis Its done accordance to size
Describe what occurs in gel electrophoresis
The DNA fragments are placed in a gel of garose or polyacrylamide
The gel has electrodes connected to it and it produces a Pd across it and it’s placed in a buffer solution
The DNA fragments are negative charged and move through the gel in accordance to size and charge, so smaller sequences travel to the positive electrode faster
Fragments are measured in base pairs
What technique is used to visualise fragments
Southern blotting or
Gel electrophoresis
What is southern blotting used for
To transfer DNA fragments to a more resilient nylon membrane as gel is to fragile
Describe stages in southern blotting and when it’s used
After restriction enzymes
The membrane and dry absorber paper are place on the gel directly to draw the buffer solution up alive with DNA fragments denatures strands from double to single
- The membrane is incubated with excess of labelled DNA probe (either radioactive or fluroescent
- to visualise with a radioactive probe, the membrane is dried first and placed to an X ray film,if the probe has bound with DNA, the film go black
If the probe is fluorescent,the postion on the membrane is visualised under uv light
In southern blotting what is the DNA probe and what does it do
It’s a short DNA section complementary to the base sequence of target DNA and they are either radioactive or labelled with fluorescent marker
In a DNA profile why does a single bond occur
When a persons maternal and paternal chromosome have the same number of stars in a certain locus
When do 2 bands occur on a DNA profile
If the two chromsomes have a different number of repeats at a locus
In visualising DNA when do we use gel electroresis
After PCR
Describe the stages in Gel electrophoresis in analysing DNA fragments
The DNA primers have fluorescent tags
The DNA fragments with their tags pass through a laser in the gel,this causes the the dye in the tags to fluoresce and the coloured light is detected
This gives a time taken fragments to pass through the gel and the time length can be calibrated with the fragment size
Str loci can be analysed by using the tags that fluroresce at different wavelengths as they give different colours for each str loci
A computer processes this info from the sector and displays the results of this on s graph
What determines the size of the fragment t
Number of base pairs
How is time of death measured
Using temperature of the body
State of decomposition
Degree of rigor mortis
Entomology
How can body temperature be used to determine time of death and how is it measured
When the body dies it cools as their is no more heat being produced by chemical reactions
An abdominal stab or measuring via rectum is how core body temp is measured
Why isnt a normal clincal thermometer used
It’s to short and has too small temperature range
What factors affect post mortem cooling
Clothing -reduces heat loss as it insulates the body
Body postion -curled up would reduce heat lose
Air movement -cools the body down faster
Body size
Humidity
Temperature of surroundings
Water
What is rigor mortis
The stiffening of muscles,with joints becoming fixed
What happens after RM
It passes and muscles relax again
Name the stages of Rigor mortis
- after death,muscle cells become deprived of oxygen and oxygen dependent reactions stop
- Anaerobic respiration occurs in cells and lactic acid is produced
- the ph in cells drop,which inhitbs enzymes and so anaerobic respiration is inhibited
- ATP is no longer produced and its needed for muscle production, this results in the bonds between muscles proteins becoming fixed
- The proteins can no longer shorten muscle as they can’t move over one another,it means muscle and joints are now fixed
How long does rigor mortis normally take and what muscle stiffen first
It lasts 6-9 hours and smaller muscles stiffen first
What are the first stages of decomposition
Autolysis occurs first which is when cells are broken down by the body’s own enzymes,from lysosomes
After death tissues are invaded by bacteria from the gut,the release of enzymes result in decomposition
What are the stages and signs of decomposition
The greenish discolouration in the lower abodonm,it’s caused by sulfhaemoglobin occurring in the blood and it spreads and chanted colour from purple to black
The formation of Co2,NH4,H,CH4,H2S in tissues and intestines causes the body to smell and become bloated
The body will deflate due to the tissues further decomposing and gases being released
How can autolysis be delayed
If the heat is to intense as enzymes involved are denatured
What are antigens
Molecules that are recognised by the hosts immune system and they are recognised as foreign
Give the differences between viruses and bacteria
Bacteria are prokaryotes
And they don’t have any memebranes bound organelles
And they reproduce via binary fissions,so they divide into two
Bacteria have double strand DNA virus have single
In bacteria what is the cell wall made from and give the two types of cell wall
It’s made from a polysaccharide called protideoylycan which is crossed linked by peptide bonds
Two types are gram positive cell wall and gram negative cell wall
Distinguish between gram positive and gram negative cell wall
Gram postive cell wall have thicked walls as they have additional proteins and polysaccharides that are cross linked
Gram negative have thinner walls and a surface layer of proteins and lipids from protection
How do viruses replicate
They enter the the cells of the host and uses its metabolic system to make more viruses
Describe the stages of viral infection
Viruse attaches to the host of the cell
It’s nucleic acid is inserted into the cell
The viral nucleic acid replicates
Viral protein coats synthesis
New virus particles are formed
Cell lysis releases the virus particles
What is lysis
The bursting of a cell
What are pathogens
Bacteria and viruses that cause disease
Give examples of barriers in the our body that help prevent infection
Stomach acid
Skin
Lysozyme
Gut and skin flora
In what ways does the skin act as a barrier in protection from infection
It contains keratin which is a protein and it’s a hard outer layer that stops entry of microorganisms
Blood clots form if the skin is broken,wounded so it seals the wound so no microorganisms and enter
How does gut and skin flora provide protection
Flora are harmless microorganisms found in skin and the gut and they compete with pathogens for nutrients and space so they limit they amount of pathogens that can grow
They are produced by lactic acid
How do mucous membranes protect us
They are produced by goblet fells and trap any particles and microbes that are carried away by beating clia to be swallowed
How does lysozyme protect us
They are produced in our eyes,mouth nose
They damage the bacterial cell walls causing it to burst which kills it
What are the two responses that the immune system produces
Non specific response
Specific response
Distinguish between the non specific and specific response
Non specific helps in destroying any invading pathogen
Sordid response is directed at a specific pathogen
Give the 4 ways that the non specific immune system responds to infection
Lysozyme
Inflammation
Phagocytosis
Interferon
When does the inflammatory response occur
When we receive a cut to the body
Describe the inflammatory response
Histamines are released by damaged mast cells
They cause dilation of arterioles in the area and they cause increased permeability of the capillary walls so this results in increase in blood flow to the capillaries at the infected site and the white blood cells in the blood at the time act and destroy the pathogen
What is a problem with histamines and the inflammatory response
They can cause swelling in tissues like odema due to the fact histamines increase permeability in capillary wallls
What happens in phagocytosis
When white blood cells engulf bacteria and other foreign in blood and tissues these white blood cells are called phagocytes
The ingested material is enclosed within a vacuole the vacuole fuses with lysosomes which release digestive enzymes which destroy bacteria or foreign material
Name the 3 types of white blood cells
Neutrophils
Lymphocytes
Monocytes
What are neutrophils
They last only a few day
Ingest and destroy bacteria
What are the two types of lymphocytes and what are they involved in
B cells and T cells
They are involved in the immune response i.e. Immunity
What are monocytes and what are their roles
They become macrophages which engulf bacteria and cell debris and foreign matter
What are lymphocytes
White blood cells involved in the specfic immune response they help defend against specfic diseases
What’s the role of the lymphatic system
They help in preventing the spread of bacteria, macrophages are present in lymph nodes
Describe the stages that occur when preventing the spread of infection in the non specfic immune system
Tissue fluid is drained into lymphatic vessels
The fluid known as lymph flows along these lymph nodes and its passes through them via thoracicducts and lymphatic as it returns to the blood
As lymph passes through lymph nodes lymphocytes and macrophages become activated if any pathogens are present and they destroy it
What is interferon and what is its role
It’s and antimicrobial protein
It produced by cells that are infected with viruses and diffuses to other cells to prevent spread of infection
It inhibits viral proteins synthesis but has side effects
What are B cells covered in and where are they produced
They are covered in proteins called antibodies and they are produced in bone marrow
Once activated what occurs with the B cells
Antibodies are secreted by a B cell when it’s activated
They bind onto antigens and label them which enables phagocytes to recognise and destroy the cell
Give the stages that in phagocytosis
Neutrophils arrive and they engulf bacteria and they become inactive
Macrophages are next and they destroy 100 bacteria by phagocytosis they ingest debris from damaged cells along with any foreign matter
The ingest material is enclosed within a vacuole and it fuses with lysosomes which released digestive enzymes which destroy bacteria
Pus forms as a result due to the area being now filled with dead cells
What do T cells contain and where they are produced
In the bone marrow and they contain a specific antigen receptor which binds to an antigen with a complementary shape
What are the two types of T helper cells
T helper cells
T killer cells
What are t helper cells
They stimulate B cells to divide and they become capable of producing antibodies and they inhance phagocytes activity and they contain cd4 receptors
What are t killer cells
Any cell that has a foreign antigen is killed by these cells
Describe the process in the activation of t helper cells in the primary immune response
Once a macrophage engulfs a pathogen they present themselves as a antigen presenting cell
This acts as s signal to the immune system m
The CD4 receptor on a t helper cell bind on to the antigen in the APCs
And this binding activates the t helper cells causing them to divide and produce a clone of active T cells and a clone memory cell
These clones remain in the body for years meaning they can react faster if the same antigen is occurs again
What are the two types of B cells
B memory cells
B effector cells
Describe the stages of clonal selection and what are the two things are produced
B cells become APCs
They bind with active t helper cells
This binding results in the releasing of cytokines by t helper cells
These chemicals stimulate division and differentiation of B cells into B memory and b effector cells
What are B effector and B memory cells ( part of primary immune response)
B effector cells -they differntiate to produce plasma cells and these release antibodies into lymph and blood last for a few days
B memory cells- they remain for years in the body which allows individuals to respond more quickly to the same antigen
Describe the stages in t killer cells activation and state their role
B cell is infected with bacterium and it becomes and antigen presenting cell and a t killer cell with a complementary receptor binds on to it
This binding causes the T cells to divide into t killer and t memory cells cytokines helps in this reaction
They cause pores to occur in infected cell membranes by releasing enzymes to create these pores this causes lysis
Which causes the pathogen to
Be released which means it can be labelled by antibodies from B cells
When does the secondary immune response occur
When the same bacterium arrives again and the response occurs faster and it involves memory cells
Give symptoms of the disease tb
Shortness of breath
Loss of appiette and weight
Fever and fatigue
Coughing
In the primary response to Tb how does the immune system respond and what is formed
Macrophages engulf the bacteria and a granuloma forms
The conditions in the tissue mass anaerobic and they contain dead bacteria and macrophages
This controls the infection
How can bacteria survive from the attacks of the immune system (tb)
They contain thick waxy cell walls which are hard to break down and it means they can lay dormant for years in the tubercules
What is latent tb
When a person has inactive form of tb
State the ways active tb may form
Mulnutrition
Old age
Aids
Poor living conditions
What does active tb do
The bacteria multiply rapidly and destroy lung tissue creating holes in in the lung
State how a fever occurs
An inflammatory response in which substances are released by neutrophils and macrophages these chemical cause our hypothalamus to alter our core body temperature to a higher temperature in which effectors warm up the body to a new point
What are the benefits of the raised temperatures
It enhances immune function and phagocytosis
The bacteria and viruses reproduce at at a slower rate at high temperatures
Give two ways to tb can be diagnosed
Skin and blood tests
How does skin testing work for tb
A small amount of tuberculin is injected into a person
A positive result will show an inflamed area of skin around the injection site,this caused by antibodies indicating the presence of Tb antigens
How can HIV be spread
Via sex
Bodily fluid salvia,
Sperm
State the parts of a HIV virus
Glycoproteins pg 120
Viral proteins,which contain reverse transcriptase and integrase
Capside molecules made of protein United
Layer of viral proteins
State how HIV viruses invade our cells
Gp 120 binds onto the CD4 receptor on a t helper cell surface
The virus fuses with the CSM membrane of the t helper which allows virus RNA and enzymes to enter the cell
Once inside the cell reverse transcriptase is used to make a complementary strand of DNA from the viral RNA template
A double strand of DNA is made that is inserted in to the human DNA by the HIV enzyme intergrase
Once inside the human genome it transcripts and translated
As a result of HIV give two ways that t helper cells are destroyed and killed
As the HIV virus is being made it buds out of the t helper cell which kills it
As a result of HIV the t helper cell is infected and is destroyed by t killer cells
What happens in mrna splicing and what does this means
When mrna is edited between translation and transcription
In this process some sections called introns are removed they are non coding
The remaining sequences are called exons and can be spliced in various ways,(these sequences can be expressed)
It means several proteins can be made from the same mrna
What happens in the acute phase of HIV
HIV antibodies appear in the blood
The symptoms that occur are fever sweats,headaches,sore throat,
after a few weeks T killer cells destroy infected cells
What is the latent phase in HIV
When the symptoms aren’t present as the virus is under check by the immune system
Can last up to 20 years
What is the diease phase in HIV
When HIV is now aids by the increase of number of viruses in the blood
The immune system is now weakened by the decline in t helper cells
State the four types of immunity
Active natural immunity
Active artificial immunity
Passive natural immunity
Passive artificial immunity
What is active immunity and state the difference between the two types
This is when our immune system makes its own antibodies by stimulation by an antigen
Natural is when after catching the disease you become immune
Artificial- when your given a vaccine contains a harmless dose of antigens
What’s passive immunity
When we receive antibodies from an other organsims
Natural ie when baby because immune after receiving antibodies from mother via breast milk
Artificial when antibodies are injected into another organism
What may a vaccine contain
A toxin that is in harmless form
Killed bacteria
Antigen bearing fragments
How do we gain immunity
By vaccination in which we are Injected with dead or inactive pathogens
What is herd immunity
When are large percentage of the population ie immmue to an infection
What is ambient temperature
The temperature of the surroundings and it determines core body temperature
What is infection
When a pathogen invades a cells
Give 3 ways HIV evades our immune system
It reduces the number of immune system cells so it has less chance of being detected
HIV has a high mutation rate which causes new strain of the virus to appear means memory cells are unable to recognise different types of antigens produce by HIV
It disrupts antigen presentation in cells meaning the immune system can’t recognise and kill it
How does Tb evade detection
It disrupts antigen presentation in infected cells which prevents them being killed by infected phagocytes
When engulfed by pathogens they produce substances that prevent lysozyme fusing and killing it meaning it can multiply and divide
What are antibiotics and state the two types
Chemical that kill the or inhibit the growth of microorganisms
Bateriocidal and bateriostatic
State which ways antibiotics inhibit bacteria and metabolism
They disrupt their cell membrane which can lead to lysis due to change in permeability
Inhibit the cell wall synthesis
They prevent cell division it inhibits nucleic acid synthesis replication and transcription
It inhibits protein synthesis meaning enzymes and other proteins are produced so it can’t carry out important metabolic processes
What are antiviral drugs
These are drugs that reduce HIV production and they are used in combination
State the two main types of antiviral drugs and their function and state other antiviral drugs
Reverse transcriptase inhibitors they prevent viral RNA from making DNA that would be integrated into host genome
Protease inhibitors that inhibit protease which catalyse the cutting down of larger proteins into small polypeptides which are used in constructing new viruses
Integrase inhibitors and fusion inhibitors
In terms of the evolution what do antibiotics and the immune system provide bacteria
They act as a selection pressure
How can bacteria develop resistance to antibiotics in terms of natural selection
Random mutations occur in the gene in a bacteria, with antibiotics acting as a selection pressure it means that a gene could become advantageous,these bacteria are able to survive and when they reproduce via binary fisson or a sexual reproduction the gene is passed onto the new bacteria formed increasing allel frequncy
What is conjugation
This is when bacteria cell to cell contact and its aids in evolution
What are hospital acquired infections
These infections are caught while a person is in hospital
How are HAI transmitted
Cough and sneezes not being contained
Hospital staff and visitors not washing their hands before and after visiting someone
Equipment and surfaces not being disinfected after use
State ways to prevent and control Hai
Hospital staff and visitors should be encouraged to wash their hands before and after they have been with patient
Equipment should be disinfected after use
State way to control hai caused by antibiotic resistant
Antibiotics shouldn’t prescribe antibiotics to prevent infections
Patients should complete there full course of prescription
Doctors should rotate the use of different antibiotics
Doctors should use narrow spectrum antibiotics when possible(only affect specfic bacterium)
Name differences between viruse and bacteria
Bacteria have a cytoplasm virus don’t
Bacteria have double strand DNA,virus have a single strand
Some bacteria have plasmid virus don’t
Bacteria have ribosomes,plasma membrane not virus
Name the structures in a bacteria and their roles
Flagellum allows them to move
Ribosomes-produce proteins from mrna
Pilli-They allow bacteria to stick to cells used in gene transfer
Plasmid small loops of DNA
slime capsule- helps protect bacteria from attack
Describe the structure of an antibodies and state their functions
Hinge region-enables flexibility when binding to antigens
Disulfide bridges-holds the polypeptide chains together
Has 4 polypeptide chains two heavy and two light chains
Variable region- they are antibody binding sites and its shape is complementary to a specific antigen and this region is different between antigens
Constant region-its the same in all antibodies and it allows binding to receptors of immune system cells
Describe the ways antibodies help to clear infections
Agglutination of pathogens- this is when they clump pathogens together as the antibodies have two bindings sites so they can bind to two pathogens at the same time (allows phagocytosis to occur)
Neutralising toxins-the toxins that are produced by pathogens are binded onto by antibodies neutralising them meaning they can’t damage human cells
Inhibiting then from binding to human cells - when antibodies bind to antigens on pathogens they block the cell surface receptors from pathogens meaning the pathogen can’t bind to the host cell
State the difference between active immunity and passive
Active you are able to stimulate your own antibodies
Passive you are injecting with antibodies
What is an infection
When a pathogen evades barriers and is inside tissues/cells
What is meant by the immune system being non specific
It’s reacts against any microorganism/pathogen and it involves,inflammation,phagocytosis,lysozyme
Explain how macrophages present antigens to t helper cells
Macrophages bind on to a t helpers cell CD4 receptor it’s also becomes an antigen presenting cell
