Topic 6 Flashcards
(36 cards)
Question
Body farms use the bodies of pigs to study the changes in insect species on a body after death.
i. Describe how this study could be carried out
I.
-Standardisation of pigs studied eg same sex,breed,mass,age
- temperature should be controlled
-record the presence of different species of insects
-at regular intervals of the day 24/every day
ii. Explain how the results of this study could be used to help establish the time of death of a human
-record which insects are present on the human
-compare with results from investigations on pigs to determine time of death
-take into account which stages of the lifecycle are present
Describe how DNA profiling could be carried out to show that two snakes are different species.
-DNA obtained from 2 types of grass snake
- PCR used to produce fragments of DNA
- gel electrophoresis used to analyse the DNA samples
- gel electrophoresis used to separate fragments of DNA
-more differences in the pattern of bands produced would indicate that the snakes are different species
Describe the changes that occur inside the body in the first week after death
-body temperature falls
- rigor mortis- stiffening of muscle
- autolysis - breakdown of cells by enzymes in the body
- discolouration and bloating occurs
Describe the role of decomposers, such as microorganisms, in the carbon cycle.
-decomposers break down organic material from the dead body
- respiration takes place
- carbon dioxide is released into atmosphere
Devise a procedure using electrophoresis to compare amplified DNA from a modern human skull and a neanderthal skull
- restriction enzymes are used to cut DNA into fragments
- DNA samples are loaded into agarose gel
- electric current is passed through
- markers are added to visuals the bands
- the position of bands produced can be compared
Explain the effect of ambient temperature on the rate of decomposition
- an increase in temp will increase the rate of decomposition
- an increase in temperature increase enzyme activity
- an increase in temperature increases growth rate of decomposers / bacteria
Describe the infection control procedures hospitals have introduced
-hand wash stations
- doctors / nurses not to wear ties/watches/ long sleeves
-testing patients for the presence of antibiotic resistant bacteria before admission of infected patients
- increased wash of bedding and disinfecting bedding
Explain how changes in blood vessels result in the swelling seen at the site of inflammation
-histamine is released
- histamine causes arterioles to dilate
-this increases the blood flow to the site causing redness
- histamines also cause the permeability of capillaries to increase
- which allows blood plasma to leave capillary and enter tissues causing swelling
Explain why the prescence of microorganisms on the skin and in the gut help prevent pathogenic organisms multiplying in the body
-flora in the gut and skin are better adapted to the conditions
- therefore they can outcompete pathogenic organism
- bacteria in the gut secrets chemicals which help to destroy pathogens
What is meant by the term phagocytosis
-idea of binding the bacteria to the phagocytic cell
- idea that bacteria is engulfed by endocytosis into the cell
-bacteria is then inside a vacuole
What is meant by non specific response
-the body defends itself from a pathogen
- the response is not dependent on the specific virus
What is meant by infection
-bacteria inside tissue cells
Describe the role of antigen presentation in three body’s specific immune response to infection by viruses
-the macrophages present to T helper cells
- T helper cells are needed to activate T killer and B cells
- B cells act as an antigen presenting to cell
- B cells result in plasma cells that produce antibodies
- the infected (host cell) present s antigen to T killer cells
- T killer cells destroy infected host cell
Distinguish between the structure of bacteria and viruses
-bacteria’s are cells but viruses are not particles
- bacteria is surrounded by cell wall and plasmids where as viruses do not have plasmids
- bacteria are DNA but viruses can be DNA/RNA
- bacteria is circular genetic material but viruses are linear
Describe how infection with a bacterium results in the production of-plasma cells
Macrophage engulfs bacteria and displays bacterial antigen on its surface become APC
T helper cell activated – CD4 receptors bind to complementary antigen on macrophage clones of T helper cells and T memory cells produced
B cell meets bacteria and presents bacterial antigen on its surface APC
Activated T helper cell with complementary receptor binds to B cell
T helper cell produces cytokines
B cell divides to form clone of B effector cells and B memory cells
B effector cells differentiate to become plasma cells
Plasma cells produce antibodies
Antibodies stick to bacteria causing marking them and sticking them together so they can be engulfed by macrophages
How does the body respond to bacteria
Macrophage engulfs virus and displays bacterial antigen on its surface become APC
T helper cell activated – CD4 receptors bind to complementary antigen on macrophage clones of T helper cells and T memory cells produced
B cell meets virus and presents bacterial antigen on its surface APC
Activated T helper cell with complementary receptor binds to B cell
T helper cell produces cytokines
B cell divides to form clone of B effector cells and B memory cells
B effector cells differentiate to become plasma cells
Plasma cells produce antibodies
Antibodies stick to viruses causing marking them and sticking them together so they can be engulfed by macrophages
Cell infected by virus puts viral antigen on its surface APC
T killer cell with complementary receptor binds to infected cell
Activated T helper cells bind to T killer cells with complementary receptors. T helper cells release cytokines T killer cells divide to form clones of active T killer cells and T memory cells
Activated T killer cell releases enzymes which make pores in cell surface causing it to burst killing cell and virus
Explain the role of T cells within a vaccine
- vaccinated person will have memory T cells
- memory T cells will recognise antigen’s specific to set virus
- T helper cells activate B cells and T killer cells
- T killer cells destroy cells infected with virus
What is PCR and why is it used
PCR is used to amplify fragments of DNA. This is important because the DNA sample collected at a crime scene doesn’t contain enough material for accurate analysis.
What are the 3 stages of PCR
Denaturation
Annealing
DNA synthesis
What happens in denaturation in PCR
Add DNA nucleotides/polymerase/primers to your sample
Addition of heat (95) needed to separate the 2 strands of the DNA molecule
What happens in annealing in PCR
2 DNA strands that have now been separated by the heat are going to be cooled and be joined by primers
The temperature (55)for this step should allow the primers to bind to specific segment
What happens in DNA sythsies in PCR
Make more copies of DNA
DNA polymerase can now bind to primer
DNA polymerase will begin to work on both of these strands and it will use the DNA nucleotides as its building material to amplify the DNA
Temperature at this step should be a little warmer than previous (70)
The temperature (70) has to be specific for the DNA polymerase to be used - optimum temp
what happens after 3 stages of PCR
End of A cycle 1 - you have 2 double stranded DNA molecules
A cycle 2
Start with 2 DNA strands then you repeat A cycle 1 and end with 4 double stranded DNA
