Experiments

Question 1

How is a control group formed?

Answer 1

•provide placebo or inactive drug
•otherwise treated exactly the same way

Question 2

What is the best graph to use for relationship between 2 discrete variables (independent)?

Answer 2

•scatter graph

Question 3

What should be considered when deciding no. of test subjects for experiment? (E.g mice)

Answer 3

•large no. to improve reliability/reduce sampling error
•ethical considerations e.g leads to death/suffering
•no. of mice related to cost/space available

Question 4

Why should you be careful to accept claim when investigating on animal?

Answer 4

•use of animal not humans do not possible to predict effect on humans
•side effects
•only tested e.g on one cell type
•may not be carried out on living organism in e.g on cells so don’t know effects

Question 5

During investigation using volunteers why should test drug be given in addition to?

Answer 5

•not ethical to replace conventional treatment
•as life of patient is at risk

Question 6

Why is log scale used for graphs?

Answer 6

•very large increase in no. = exponential

Question 7

Why is a control used?

Answer 7

•to show that any results are due to the independent variable and not due to another factor

Question 8

What are the method limitations in the enzyme practical?

Answer 8

•end point is subjective so inaccurate time taken measurements
•water bath not thermostatically controlled
•not enough intermediate PH values tested so optimum PH cannot be accurately measured
•range of tested pH not wide enough

Question 9

What are the equipments used in mitosis practical and why?

Answer 9

•HCl= break down cell wall to allow stain to diffuse into cell or cell to be squashed. It will also stop mitosis
•stain=make chromosomes visible
•mounted needle=lower coverslip and prevent air bubbles
•root tip used=mitosis is occurring (meristems)

Question 10

Why do you press down firmly on cover slip?

Answer 10

Get thin layer of cells so light can pass through

Question 11

When counting cells for mitotic index, what do you do to ensure count is accurate?

Answer 11

•examine large no. of fields of view
•ensures representative sample

Question 12

What aseptic techniques are used to form a Petri dish?

Answer 12

•sterilise all equipment to kill microbes
•sterilise work surfaces with disinfectant
•wash hands with soap to remove microbes
•work near Bunsen burner as warm air wafts away microorganisms
•open Petri dish lid at an angle

Question 14

Why are different mitotic indexes calculated?

Answer 14

•root tips are different ages
•root tip from different species
•single field of view is not representative of a root tip
•cells undergo mitosis at different times