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CSC8309 -- Gene Expression and Proteomics

In this practical, we have focused very heavily on quality metrics. However, there is still a lot of downstream analyses that we can perform.

Although, in this case, we are analysing sequences from a plant which has been fully sequenced, it is also possible to make microarrays de novo, to cDNA libraries. In these cases, microarray analysis would uncover a set of uncharacterised genes (with known sequences).

quest
  1. How would you analyse these genes, to determine their function?

Another common task is to split genes into groups which behave similarly. This is normally the next step following a time-course experiment. For example, rather than asking which genes are over-expressed, which might also want to know about genes which are under-expressed following infection. Or genes which are are over-expressed at 6hr, but under at 12hr.

Clustering links together genes based on their expression profile — how their expression changes over time.

quest
  1. What form of statistic would you use to perform clustering?
  2. What R packages exist for clustering?

Finally, a common question is to ask "what do these genes of interest actually do"? An easy question to answer if you have 5 genes, but if you have 50? Is there any commonality between their functions?

quest
  1. How would you summarise the function of 50 genes?
  2. Can you find any tools which allow you to do this?

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