348

25

Phenomics

it has long been recognized that the determination of PON1 status requires more than

genotyping: ³ both the catalytic activity of individual molecules and their abundance

in serum are important. ⁴ Within a given population, serum PON1 activity can vary

by one to two orders of magnitude; it is modulated by numerous transgenic factors,

including environmental chemicals, drugs, diet and age.

25.2

Phenotype Microarrays

Microbes, with their relatively limited phenotypic repertoire, and even individual

cells from multicellular organisms, are amenable to high throughput array-based

assays analogous to gene microarrays (Sect. 18.1). Systems in current use are based on

arrays of microwells, each well containing the cells and other necessary components.

One approach is based on cell respiration as a universal monitor of cellular activity;

it is monitored colorimetrically via the reaction of NADH with a reporter dye. ⁵

Another approach is based on OWLS (Sect. 23.8.2) in an array format. ⁶ The latter is

potentially much more powerful because a much more detailed view of phenotype

can be obtained, including the kinetics of shape changes and of the redistribution of

material within the cell. ⁷

25.3

Ethomics

The phenotype of multicellular organisms needs more sophisticated approaches than

what can be achieved using a microarray (Sect. 25.2). ⁸

The enormous growth in computing power has rendered feasible camera-based

methods for automatically quantifying the individual and social behaviours of crea-

tures as sophisticated as flies. ⁹ Such methods rely on machine-vision algorithms

capable of accurately tracking many individual flies, and classification algorithms

for the diverse behaviours displayed by the flies. Once the trajectories have been

captured, one needs to reduce the data in order to allow, for example, classification

into behaviours. This can be achieved by classifying segments of trajectories into

discrete behavioural states. ¹⁰

3 Richter and Furlong (1999).

4 Furlong (2008).

5 Bochner et al. (2001).

6 E.g., Orgovan et al. (2014).

7 Ramsden and Horvath (2009).

8 See Zumpe and Michael (2001) for an excellent introduction to the behavioural science of higher

organisms.

9 E.g., Branson et al. (2009).

10 Branson et al. (loc. cit.).