Question

Your team has posed the question: Does MAD1 control the metaphase checkpoint?

The hypothesis was: If MAD1 gives the signal to progress to anaphase after chromosomes have aligned, then a group of mutant MAD1 cells will more often have imperfect chromosome numbers after a series of cell divisions compared to normal cells.You investigated this question by comparing the cell division of cells that have the normal, or “wildtype” MAD1 gene to the division of cells with the mutant MAD1 gene. In your experiments, you compared the number of “aneuploid” cells (imperfect chromosome numbers) to the number of “euploid” (correct chromosome numbers) in your experimental group of MAD1 mutant cells and your control group of MAD1 normal cells.

Question:

Identify the independent, dependent, and standardized variables in the experiment described above.

Answer 1

Some basic definitions:

The independent variable is the part/ aspect of a particular experiment that can be changed according to pre-set conditions to find a solution

The dependent variable is the part/aspect of the experiment which is affected by the change in the independent variable.

The standardized variable is the part/aspect of the experiment which remain constant throughout the experiments.

According to above definitions, the variables in above described experiment are -

Independent variable: Signal from MAD1 (since it is not dependent on external factor here)

Dependent variable: Ploidy of chromosomes (since it is dependent on correct signal from MAD1)

Standardized variable: These would be the conditions in which both the normal and mutant cells were cultured. For example, nutrients, oxygen, temperature, humidity, and light conditions etc. all constitute standardized variables.