| Timecourse experiments yield a higher level of detail than single-
timepoint experiments, including temporal information
2) Determine the appropriate time points that will reveal the genomic
expression response … it is easy to miss rapid responses that occur and subside within a short period (eg 15 minutes)
B. Plan the experiment: ONE VARIABLE ONLY!
As in any experiment, it is very important to insure only One variable in genomic expression experiments. Often, experimental variables that overlooked can provoke substantial changes in genomic expression and confound analysis of the results.
1. Hypothetical and real examples of multiple variable experiments:
a. ** Diauxic shift during experiment: likely the most common oversight
is the progression of the cells through diauxic shift, when the cells become limited for glucose and alter their metabolism accordingly. The expression of thousands of genes is altered during this phase of growth. The timing of diauxic shift is dependent on the culture conditions (strain, media, growth temperature, aeration, environmental stress) so it is very important to know when diauxic shift occurs under your conditions and avoid it (see more below).
b. Pleiotropic drugs will result in pleiotropic cellular effects and thus genomic
expression
1) The “DNA damaging agent” Methyl-methane sulfonate (MMS)
methylates many cellular targets in addition to DNA
2) High sodium – alters ionic strength, osmotic strength, as well as Na concentration
c. Experiments with extensive cell handling: account for cell handing in a
control experiment
1) Changes in culture aeration can lead to hypoxia
d. Drugs suspended in a carrier solution: add carrier alone in mock control
上一篇：Post-Processing of Arrays 下一篇：Antigen Array Probing 共7页: 上一页 [1] 2 [3] [4] [5] [6] [7] 下一页 | 
