Case unit 1 Flashcards
what is a case study
study of a particular situation/individual
used to narrow down a very broad field of research into one more easily researchable topic
testing whether scientific theories and models work in the real world
advantages of case studies
focus on specifics
large amounts of data
help adapt ideas and produce novel hypothesis
challenge theoritcal assumptions
disadvantages of case studies
opinion based research
large amounts of data from multiple sources
hard to replicate
hawthorne effect - people change their behaviour when they know they are being watched
researcher bias
time consuming
what is a case control study
a study that compares individuals who have a disease or outcome of interest with indivudals who do not
looks back retrospectively
determins a relationship
often observational
advantages of case control study
good for studying rare conditions of disease less time needed simultaneously look at risk factors useful as inital studies less costly
disadvantages of case control studies
retrospective - rely on past data and memory
can be difficult to find a suitable control group
selection bias
limited to examining one outcome
what is a cohort study
one or more samples are followed prospectively and subsequent status evaluations with respect to disease or outcome are conducted to determine which risk factors are associated with it
advantages of cohort studies
subject cohorts can be matched standarisation of criteria is possible easier and cheaper than randomaised multiple exposures and outcomes measured demonstrate direction of causality
disadvantages of cohort studies
cohorts can be difficult to identify due to confounding variables
no randomisation
outcome of interest could take time to occur
costly and time consuming
participants may move between groups
not good for rare diseases
what is a randomised control study
randomly assigning participants into an experimental group or control group
effect of specific treatment/practice
advantages of randomsied studies
easier to blind
results can be analysed with well known stats
populations of participating individuals are clearly idenified
provide strong epidemiological evidence
disadvantages of randomised studies
expensive time consuming volenteer bais - popluation may not be representative of the whole does not reveal causation inefficient for rare diseases
what are kock postulates
- the microorgaism must be found in abundance in all orgasims suffering from the disease but should not be found in healthy organisms
- the microrganism must be isolated from a diseased organism and grown in pure culture
- the cultureed microorganism should cause disease when introduced into a healthy orgaism
- the microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original
what is the paradigm shift
a change in the way we view concepts and practices
how does a paradigm shift occur
evidence builds up that contridicts the prevaling theory
the current theory undergoes crisis
a new paradigm is eastblished
scientists work normally again
what is PCR used for
to amplify a section of DNA
to detect specific DNA sequences
alter DNA sequences
clone DNA
what are the 3 stages of PCR
denaturing
anneling
extending
what happens in the denaturing stage
a cocktail containing the template DNA and all other core ingredients is heated to 94-95 degrees
the high temp causes the H bonds between the bases of the two strands to break
the strands seperate, these will act as the templates
temp must be maintained for long enough to ensure strands seperate
usually takes between 15-30 secs
what temp is reached in the denaturing stage
94-95 degrees
what happens in the annealing stage
reaction cooled to 50-60 degrees
primers attached to a specific location on the single strand by way of H bonds
once primer is bound, polymerase enzymes attach and start making the complementary strand
the two seperate strands are complementary and run in opposite directions
this steps usually takes about 10-30 secs
what are primers
a single strand of DNA around 20-30 bases long which are designed to be complementray in sequence to the start of each section to be copied
what happens in the extending stage
heat is increased to 72 degrees to enable Taq DBA polymerase
primers and bases attached
results in brand new strand of DNA and a double stranded molecule of DNA
how long is the extending stage
depends on the lenght of DNA sequence being amplified but normally 1 mintue for 1000 bases
how are the results of PCR seen
visualised using gel electrophoersis
fragments of DNA are pulled through a gel matrix by an electrical current and seperare DNA according to size
forms a band on the gel
what is qPCR used for
to qualify the amount of a specific DNA sequence in a sample
quanify experssion levels of specific mRNA to see how active a gene is
how does qPCR work
use reverse transcriptase to create cDNA from mRNA
run normal PCR
die attached to primers, becomes flourescent when bound in double DNA strand
what is the ct value
value when the PCR curve crosses the threshold
what does a higher ct mean
less mRNA detected
calculation for delta ct
ct gene test - ct endogenous control
