Forensics, Immunity And Infection Flashcards
Explain the role of DNA primers in PCR
Have a specific base sequence
Bind to complementary bases of the DNA to be amplified
So they provide a site for the DNA polymerase to bind
Explain why the amplified DNA fragments for 2 alleles are different
Base sequences of the alleles are different
Restriction enzyme cuts at a specific site
That is only present in one allele
Devise an experiment to determine the optimal number of cycles for PCR to amplify DNA
Need DNA, polymerase, primers, mononucleotides
Control temp at diff stages: 95, 55, 70
Change number of cycles
Use gel electrophoresis to determine quantity of DNA produced
Choose smallest number of cycles that produces an observable band
body farms use the bodies of pigs to study the changes in insect species on a body after death
describe how this study could be carried out
standardisation of pigs studied eg same size/ breed/ mass/ age/ sex
control temp
record presence of diff species of insects
at regular time intervals eg every 24 h
describe how DNA profiling could be carried out to show that snakes are diff species
DNA obtained from 2 types of snake
restriction enzymes used to produce fragments of DNA
gel electrophoresis used to analyse DNA samples and separate fragments
more differences in pattern of bands produced indicated that the snakes are different species
describe the changes that occur inside the body un the first week after death
body temp falls
rigor mortis
break down of cells by enzymes in the body
discolouration/ bloating
describe the role of decomposers in the carbon cycle
break down organic material from the dead body
respire
releasing CO2
explain the effect on temp on the rate of growth of insects on the dead body
temp affects enzymes
an increase in temp increases kinetic energy
producing more frequent collisions between enzyme and substrate molecules
devise a procedure using gel electrophoresis to compare amplified DNA
restriction enzymes used to cut DNA into fragments
DNA samples loaded onto agarose gel
potential difference applied across gel
fluorescent dyes added to visualise bands
the position of the bands produced can be compared
explain the affect of ambient temperature on the rate of decomposition
increase in temp increases rate of decomposition
increases enzyme activity
increases growth rate of bacteria/ fungi/ decomposers
describe how one PCR cycle would increase the quantity of DNA present
heat to 95º to break H bonds between DNA strands
joining of primers/ annealing at 55º
addition of nucleotides, DNA polymerase involved in formation of phosphodiester bonds
to double the quantity of DNA
describe the infection control practices that hospitals have introduced
hand wash stations
docs/ nurses not to wear ties/ long sleeves/ watches
testing patients for presence of antibiotic resistant bacteria before admission and quarantine of infected patients
increased disinfection of surfaces
explain how changes in the blood vessels result in the redness and swelling seen at the site of inflammation
histamine released
causes vasodilation
increases blood flow to site, causing redness
also causes permeability of caps to increase
allowing plasma to leave caps, causing swelling
describe how HIV particles are able to enter T helper cells
GP120 on surface of the virus
bind to CD4 receptors on surface of T helper cells
viral envelope fuses w membrane of T helper cell
viral RNA enters the cell
explain why the destruction of T helper cells causes the symptoms of AIDS
reduces cytokine production
reducing cloning/ activation of B cells
reducing antibody production
increased risk of opportunistic infections
which cell produces antibodies
plasma cell
explain why the presence of microorganisms on the skin and in the gut helps to prevent pathogenic organisms multiplying in the body
flora in gut and skin better adapted to conditions
therefore can outcompete pathogenic organisms
bacteria in the gut secrete chemicals/ lactic acid which help to destroy pathogens
explain the role of the T cells in the body of a person who becomes infected with a virus that they got vaccinated for
a vaccinated person will have T memory cells
recognise specific antigens
T helper cells that activate B cells/ T killer cells
T killer cells destroy cells infected with virus
explain why there are relatively few species of bacteria in the stomach
pH in stomach is too low for enzymes of most bac to function
bac that live in the stomach have adaptations that enable them to survive
state what is meant by the term bacteriostatic antibiotic
a substance which can inhibit the growth/ prevent multiplication of bacteria
what type of chemical reaction takes place in decomposition
hydrolysis
why is there a decrease in mass during decomposition
decomposers release enzymes for decomposition
monomers formed that are soluble and soak into ground/ taken up by organisms
respiration of glucose by decomposers
CO2 released
explain what effect an increase in temperature would have on the rate of decomposition
increase rate
increased kinetic energy increases number of collisions and enzyme- substate complexes formed
above a certain temp, rate of decomposition would decrease/ stop
enzymes become denatured
suggest 2 ways in which scientists can share their results
scientific/ peer reviewed articles/ journals
scientific conferences
media reports eg TV, radio
