Case unit 1

Question 1

what is a case study

Answer 1

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

Question 2

advantages of case studies

Answer 2

focus on specifics
large amounts of data
help adapt ideas and produce novel hypothesis
challenge theoritcal assumptions

Question 3

disadvantages of case studies

Answer 3

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

Question 4

what is a case control study

Answer 4

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

Question 5

advantages of case control study

Answer 5

good for studying rare conditions of disease
less time needed 
simultaneously look at risk factors 
useful as inital studies 
less costly

Question 6

disadvantages of case control studies

Answer 6

retrospective - rely on past data and memory
can be difficult to find a suitable control group
selection bias
limited to examining one outcome

Question 7

what is a cohort study

Answer 7

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

Question 8

advantages of cohort studies

Answer 8

subject cohorts can be matched 
standarisation of criteria is possible 
easier and cheaper than randomaised 
multiple exposures and outcomes measured 
demonstrate direction of causality

Question 9

disadvantages of cohort studies

Answer 9

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

Question 10

what is a randomised control study

Answer 10

randomly assigning participants into an experimental group or control group
effect of specific treatment/practice

Question 11

advantages of randomsied studies

Answer 11

easier to blind
results can be analysed with well known stats
populations of participating individuals are clearly idenified
provide strong epidemiological evidence

Question 12

disadvantages of randomised studies

Answer 12

expensive 
time consuming
volenteer bais - popluation may not be representative of the whole 
does not reveal causation 
inefficient for rare diseases

Question 13

what are kock postulates

Answer 13

1. the microorgaism must be found in abundance in all orgasims suffering from the disease but should not be found in healthy organisms
2. the microrganism must be isolated from a diseased organism and grown in pure culture
3. the cultureed microorganism should cause disease when introduced into a healthy orgaism
4. the microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original

Question 14

what is the paradigm shift

Answer 14

a change in the way we view concepts and practices

Question 15

how does a paradigm shift occur

Answer 15

evidence builds up that contridicts the prevaling theory
the current theory undergoes crisis
a new paradigm is eastblished
scientists work normally again

Question 16

what is PCR used for

Answer 16

to amplify a section of DNA
to detect specific DNA sequences
alter DNA sequences
clone DNA

Question 17

what are the 3 stages of PCR

Answer 17

denaturing
anneling
extending

Question 18

what happens in the denaturing stage

Answer 18

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

Question 19

what temp is reached in the denaturing stage

Answer 19

94-95 degrees

Question 20

what happens in the annealing stage

Answer 20

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

Question 21

what are primers

Answer 21

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

Question 22

what happens in the extending stage

Answer 22

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

Question 23

how long is the extending stage

Answer 23

depends on the lenght of DNA sequence being amplified but normally 1 mintue for 1000 bases

Question 24

how are the results of PCR seen

Answer 24

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

Question 25

what is qPCR used for

Answer 25

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

Question 26

how does qPCR work

Answer 26

use reverse transcriptase to create cDNA from mRNA
run normal PCR
die attached to primers, becomes flourescent when bound in double DNA strand

Question 27

what is the ct value

Answer 27

value when the PCR curve crosses the threshold

Question 28

what does a higher ct mean

Answer 28

less mRNA detected

Question 29

calculation for delta ct

Answer 29

ct gene test - ct endogenous control