Topic 6 Flashcards
What are Exons?
Sequences that contain code for a polypeptide (Coding parts of DNA)
What are Introns?
- Non Coding sequences of mRNA
- with introns, you have short tandem repeat sequences (STR) also called satellite DNA
- an STR can contain from 2-50 base pairs and can be repeated from 5 several hundred times
- more similar repeats= more related
What is Post Transcriptional Modification?
- Allows for one gene to code for many proteins
- Through alternative splicing of exons
- In Spliceosome
What are the steps for Post Transcriptional Modification?
- Introns are removed from the gene
- Exons are re-ordered
- Then are translated to create different proteins
What is DNA Profiling?
Where DNA is used for identification as well as comparing genetic relationships between organisms
What are the main stages of DNA Profiling?
- Sampling
- Amplification
- Sorting + Comparison (Gel electrophoresis)
How does sampling work?
Obtaining DNA Sample
- Requires biological tissue (Cheek Swap, Blood Smear + Skin Cells)
- Tissue is broken down in buffer solution to disrupt cell membranes
- DNA is separated through a centrifuge
- Protease is added and the solution is incubated removing proteins
- Cold ethanol is added to precipitate the DNA
How does DNA amplification work?
PCR Steps
- DNA sample + Taq polymerase, DNA primers and Nucleotides are added to REACTION CYLINDER
- 95C - DNA strands are separated
- 55C - Primers attach at the start of STR sequences
- 70C
- Taq polymerase attaches and replication occurs at each primer using the nucleotides
- STR fragments are replicated again and again
What is the definition of Core temperature?
- The internal body temperature of a person before death
- Normal Temp 37
- Drops rapidly after death
What is the definition of Rigor Mortis?
- Stiffening of muscles after relaxing post death
- Joints become fixed
- Depends on position (flexed or extended)
What is Autolysis?
- Body enzymes from lysosomes and small intestine
- Break down cells and tissue
- Gut bacteria invade other tissues after death
- Releasing decomposition tissues
What is putrefaction?
- First signs of decomposition
- Discolouration of lower abdomen skin
- Sulfhaemoglobin formation in the blood
- Spreads across the body turning reddish green → purple-black colour
- Gas or Liquid blisters
- Formation of CH4, HS, CO2, NH3, H2 gas in intestines + Tissues
- Body smells and bloats
- Caused by bacteria
What factors determine the time of death?
Factors that estimate time of death:
- Core temperature + Post Mortem Cooling
- Rigor Mortis
- Stage of Decomposition
How does body temperature relate to the time of death?
Body Temperature
- Core temp is 36.2 - 37.2 Degrees
- Lack of heat-producing chemicals causes post-mortem cooling
- This means the accuracy decreases over time
- Measured through a long thermometer/temperature probe via the rectum or abdomen
- Follows a sigmoid curve
- Plateau lasts 30-60 Min
- Assumes death at normal temp
- Assumes no hypothermia or fever
What effects post mortem cooling
********Factors that affect post-mortem cooling********
- Body size
- Body position
- Clothing
- Air Movement
- Humidity
- Temperature of surroundings
What are the steps in Rigor Mortis?
Steps in Rigor Mortis
- Muscle cells become starved of oxygen, stopping oxygen-dependent reactions
- Lactic acid produced from anaerobic respiration
- Causing a drop in cell pH inhibiting enzyme reactions including respiration
- ATP is no longer produced for fixing muscle proteins
- Protein cant move over one another fixing muscles and joints
How does Rigor Mortis Relate to the time of death?
Rigour Mortis will occur quicker if env temp is high or if physical activity before death
How does Decomposition relate to the time of death?
Decomposition
- Abdominal wall discolouration 36-72 hours after death
- Gas formation occurs after a week
- Colder temperatures slow down decomposition
- Warmer temperatures speed up decomposition
- Injuries allow entry of bacteria aiding decomposition
What happens hours after a death?
Hours after Death
- body temp dec.
- bacteria + enzymes decompose body cells + tissue→ this is called autolysis
- fly eggs present
- rigour Mortis (4-6 hours after death)
What happens days after death?
Days after death
- microorganisms decompose tissue + organs→ self-digestion
- discolouration of the skin of the lower abdomen- the first sign of decomposition (putrefaction)
What happens Weeks after death?
Days after death
- microorganisms decompose tissue + organs→ self-digestion
- discolouration of the skin of the lower abdomen- the first sign of decomposition (putrefaction)
What happens months ad years after death?
**Months =** Skeleton
****Years =**** Skeleton disintegrates
What is the definition of forensic entomology?
- The study of the colonisation of organisms on a dead corpse to determine the time of death.
- The rate of maggot development is determined through maggot mass and temp of air around the body
- The age of maggots through time eggs are laid gives the minimum time since death
What is the succession of organisms in a corpse?
Organism Succession
- Bacteria
- Flies + Larvae
- Beetles
- No organisms
What are the changes in tissue after death?
- Post-death
- Decomposed tissue
- Dry Tissue (Flies leave here)
- No Tissue
What is succession?
- One group of organisms feeds on the decomposing body
- Changing the conditions attracts another group of organisms
- Forensic entomologists can then determine the stage of the sequence of organisms the corpse is in to determine the time of death
- Through the age of maggots and the time eggs were laid
That investigation could be carried out to study the effect of temperature on the time taken for the first instar maggot to become a pupa?
1) use a range of temps
2) water bath
3) timing starts when eggs hatch into instar maggots + ends when the third instar maggots begin to pupate
4) provide food for maggots
5) control humidity
What factors affect the life cycle of an insect?
conditions affecting the life cycle of an insect
- dugs
- humidity
- oxygen
- temp
What is Bacteria?
Bacteria
- Belong to the prokaryote kingdom
- Pathogen
- Reproduce rapidly
- Releases toxins that cause lysis of cells
- Cell walls made of Peptidoglycan (Peptides and Sugar molecules)
What is a Virus?
Virus
- Nucleic Acid (DNA or RNA) surrounded by a capsid protein coat
- Electron microscope required to see
- Has some type of genetic material RNA or DNA
- Some have enzymes or an outer envelope - useful for virus replication
- Virus reproduction requires a host and can mutate
What is the structure of a bacteria cell?
Flagellum - Allows the bacteria to move around
Pili - Allows the bacteria to attach to other cells
Plasmid - Contains genetic information of the cell and can be transferred from bacteria to bacteria
Capsule - Protects the cell
Cell Wall - Supported the cell
Ribosome - Translated mRNA into protein
What is the lytic cycle?
Lytic Cycle
- Attaches to a receptor on the cell
- Injects genetic material into the cell
- Starts following the genetic material instruction
- Copying the virus to the point where cell lysis occurs
What is the lysogenic cycle?
Lysogenic cycle (Longer Cycle)
- Inject material
- Genetic material binds with the cell
- Meaning mitosis copies the cell and virus genetic material
- Once triggered into the lytic cycle (Chemical, Lack of food)
What is innate immunity?
- Any generalised response to any pathogen
Non-specific immunity / innate immunity
How does the skin prevent pathogens from entering the body?
Skin
- Skin is physical barrier pathogens have difficulty passing it
- Skin flora - Microbes which don’t allow other bacteria
How does the lysomes prevent pathogens from entering the body?
Lysozyme
- Chemical defence
- Enzymes breaking down the cell membrane
- -some = sac
- -lysis = break down
- -cyte = cell
How does the Mucous Membranes prevent pathogens from entering the body?
Mucous Membranes
- Lacks kertain
- traps microbes
- contains lysozyme
How does the stomach acid prevent pathogens from entering the body?
Hydrochloric Acid
- pH of 2
- Acidic
- Bacteria cant survive
How does the ciliated cells prevent pathogens from entering the body?
Ciliated cells
- Line inside the nose
- Carries dust and pathogens out of the body
How does the Gut Flora prevent pathogens from entering the body?
Gut flora
- Bacteria found in large and small intestines
- 100 different species
- Warm moist and plenty of food
- Aid digestive process and exclude pathogenic bacteria from competition
- Mutualistic relationship
How does inflammation work?
Inflammation
- Itis = Inflammation
- Injury can cause microbes to enter the field
- Damages white blood cells release histamines
- Plasma fluid, wbcs and antibodies leak into capillaries causing swelling
How do histamines work?
Histamines
- Released by damaged white blood cells
- High temp reduces pathogen reproduction
- Blood vessel dilation increased blood flow
- An increased amount of white blood cell
How does a Fever Work?
Fever
- Hypothalamus sets the higher temp
- Reducing pathogen reproduction and enzyme usage
- More successful at fighting the infection
- Spikes in very high when viruses burst out of cells and then drop again
How do Interferons work?
Interferon
- Interferes with viral replication
- Releases interferon and diffuses to surrounding cells
- Binds to receptors on the surface to unaffected cells and makes them resistant to infection
- Since the viruses can’t bind to the cell
- Meaning that the virus that does break out doesn’t infect other cells
What is TB and what causes it?
- Tuberculosis is a contagious disease
- Caused by Bacteria (Mycobacterium tuberculosis)
- Can be respiratory or pulmonary (affects lungs)
How is TB transmitted?
- Bacteria is inhaled or lodged in the lungs
- Bacteria Multiplies
- Going into the primary and active stages
What are the symptoms of the TB?
Symptoms of TB (Active)
Symptoms aren’t shown during the primary stage
- Only 30% of people will become infected
- 5-10% develop symptoms
- Coughing (Blood)
- Shortness of breath
- Loss of appetite and weight loss
- Fever and Extreme Fatigue
How does Primary Infection work for TB?
Primary Infection with TB
- No symptoms and lasts for several months
- Bacteria causing an inflammatory response
- Macrophage engulfs bacteria through phagocytosis (Forming granuloma Tissue)
-
Thick waxy cell wall resists killing mechanisms
Difficult to break down- Can lie dormant for years in tubercles breeding
- Only released when the immune system is weakened
- Breaking out of the tubercles
- Targeting and suppressing T Cells and reducing antibody production and attack by Killer T Cells
What can cause Active tuberculosis?
Active Tuberculosis
- Occurs if the patient’s immune system cannot contain the disease on arrival in the lungs
- Due to the number of bacteria being too large
- Very old or very young age having slower immune responses
- AIDS and HIV weaken the immune system
How does active tuberculosis work?
- Happens in the lungs
- bacterial multiplies rapidly
- Destroys lung tissue
- Creating holes and gravity which is fatal
- Antibiotics needed to prevent death
What is HIV and what causes it?
Caused by a Human Immunodeficiency Virus and is an STD
How does HIV affect the body?
HIV affects the T helper cells and changed he changes the cell’s protein synthesis
What is the structure of HIV?
HIV Structure
- Structurally complex enveloped virus
- RNA
- 20-sided protein capsid coat
- Lipid envelop
- Viral glycoprotein molecules
How does HIV invade T helper Cells?
- Contains a glycoprotein gp120 on the viruses surface
- Which binds to the CD4 receptors on T cell
- The virus envelope fuses with the T helper cell membrane
- Meaning RNA can enter the cell
How does HIV affect protein synthesis in a cell?
- Reverses normal transcription
- Through enzyme reverse transcriptase
- Producing HIV DNA which is integrated into the host DNA through intergrase
- Which can be translated and transcribed in the host to produce more proteins
How does HIV kill T helper cells?
- HIV Virus protein, glycoprotein and nuclear material produced
- Making more viruses that bud out of the cell
- Taking cell membranes in their envelope
- Killing the helper T cell
- Less helper T cells MORE Viruses
How does the acute phase work?
Acute Phase
- HIV bodies appear in blood (3-12 weeks)
- Fever, Sweats, headache, sore throat, swollen lymph nodes OR asymptomatic
- Rapid replication of Virus + Loss of Helper T Cells
- After weeks T killer cells destroy infected Helper T cells
How does the chronic phase work?
Chronic / Latent Phase
- Can last for many years
- Virus numbers still increase but some control by the immune system
- NO symptoms but an increase in secondary infections that take longer to go away
- Dormant diseases can activate (TB)
How does the disease phase work?
Disease Phase
- The decline in T cells and spike in Viruses
- Immune system vulnerable
- Other diseases can take advantage and replicate rapidly (Opportunistic infections)
- Which are FATAL (AIDS, TB)
- Weight loss, Dementia, Tumours
What is active immunity?
- Immune system makes its own antibodies
- After being stimulated by antigens that have entered the body
Can happen artificially or naturally - Long term protection
- Memory cells produced
What is passive immunity
- Antibodies are made by another organism
- Not made by you (artificial or natural)
- No exposure to antigen
- Immediate Protection
- No memory cells produces
How can passive immunity be gained naturally?
- Transfer of maternal antigen to baby
- Through placenta (decreases over the first few weeks)
- Through breast milk (longer lasting but still decreases)
- Premature babes are more at risk as they haven’t had antibodies passed to them
How can passive immunity be gained artificially?
- Administration of pre-formed antigens through
- Tetanus injection
- Rabies injection
- Anti venom antigens
- Which need to be repeated
- NO memory lymphocytes are produced
How is active immunity gained naturally?
- Gained through being infected
- Exposure to antigen and production of antibodies
- Producing memory cells
- Long lasting immunity
How is active immunity gained artificially?
- Through vaccines against a disease
- Uses a weakened pathogen or inactive part of the cell
- Immune response without causing symptoms
What can vaccines contain?
- Attenuated viruses - weakened viruses
- Dead Bacteria
- Toxins that have been altered to be homeless
- Antigen fragment of a pathogen
What are the different uses of vaccines in eradication programmes?
- Herd vaccination
- Vaccinate most/all people
- Stops infection spreading in a population
- Ring vaccination
- Vaccinate all people around victim
- Contains the spread in a ring
- Stopping transmission
What is the steps in cell mediated?
- Phagocytosis is carried out
- Turning the macrophage into an **********Antigen Presenting Cell (APC)************
- Helper T cell receptors attach to the antigens on the APC and activate the helper T cells
- Causing itis to replicate larger numbers of Helper T cells
- The T helper cells then differentiate into different cells
- Remain as helper T cells to activate macrophages
- Some become memory cells for the specific antigen
- Some become T-killer cells
What are the steps for the humoral response
What is the structure of antibodies?
- Y shaped molecules
- Membrane bound or blood bound
- Constant region - standard across antibodies
- Variable region - antigen binding site which is specific to pathogen antigen
- Hinge region allows for readjustment of variable region for better more accurate binding
How does antibodies work?
- Marks pathogens and gourps them together
- Aggultanation reduces spreading as well as allow for easy phagocitosis of the grouped up pathogen
What does bactericidal mean?
- Antibodies would kill the bacteria
**-cide = to kill****
What does bacteriostatic mean?
- Prevents the multiplication of the bacteria so their immune system can destroy the bacteria
What can bactericidal antibiotics do?
- Change permeability of cell membrane (too much water)
- inhibit wall synthesis
- Example - Penicillin
What can bacteriostatic antibiotics do?
- inhibit the nucleic acid synthesis - prevents cell division and preventing the production of enzymes
- Inhibits the production of bacterial enzymes
- Example - macrolides
Why can bacteria evolve quickly?
- Bacteria can reproduce fast (Division every 20 min)
- Populations in the billions meaning there are cells with mutations in vast
- Random mutations will allow the cell to use different resources and infect hosts more effectively causing higher rates of survival and reproduction
How do antibiotics cause vertical evolution?
- Antibiotics act as a selection pressure
- Where bacteria that don’t possess a gene for resistance will die
- Whereas those who do will reproduce causing the frequency of this allele to increase
- As the gene is passed vertically from one generation to the next
What is horizontal evolution?
- Gene is passed from one bacterium to another
- Can be interspecies through cell-to-cell contact (Conjugation)
What policies have been put in place for hygiene?
Tightened infection control:
- Hand wash stations
- Rules preventing ties and watches
- More sanitising of beds and surfaces
