Light-to-dark transition of genes. Synechocystis, a type of bacterium that can grow and survive under a wide range of conditions, is used by scientists to model DNA behavior.

In the Journal of Bacteriology (July 2002), scientists isolated genes of the bacterium responsible for photosynthesis and respiration and investigated the sensitivity of the genes to light. Each gene sample was grown in an incubator in “full light.” The lights were then extinguished, and LO3 any growth of the sample was measured after 24 hours in the dark (“full dark”). The lights were then turned back on for 90 minutes (“transient light”), followed immediately by an additional 90 minutes in the dark (“transient dark”).

Standardized growth measurements in each light–dark condition were obtained for 103 genes. The complete data set is saved in the GENES file. Data on the first 10 genes are shown in the following table.
Gene ID Full-Dark Tr-Light Tr-Dark SLR2067 -0.00562 1.40989 -1.28569 SLR1986 -0.68372 1.83097 -0.68723 SSR3383 -0.25468 -0.79794 -0.39719 SLL0928 -0.18712 -1.20901 -1.18618 SLR0335 -0.20620 1.71404 -0.73029 SLR1459 -0.53477 2.14156 -0.33174 SLL1326 -0.06291 1.03623 0.30392 SLR1329 -0.85178 -0.21490 0.44545 SLL1327 0.63588 1.42608 -0.13664 SLL1325 -0.69866 1.93104 -0.24820 Based on Gill, R. T., et al. “Genome-wide dynamic transcriptional profiling of the light to dark transition in Synechocystis Sp. PCC6803.” Journal of Bacteriology, Vol. 184, No. 13, July 2002.

a. Treat the data for the first 10 genes as a random sample collected from the population of 103 genes, and test the hypothesis that there is no difference between the mean standardized growth of genes in the full-dark condition and genes in the transient-light condition. Use a = .01.

b. Use a statistical software package to compute the mean difference in standardized growth of the 103 genes in the full-dark condition and the transient-light condition.
Did the test you carried out in part a detect this difference?

c. Repeat parts a and b for a comparison of the mean standardized growth of genes in the full-dark condition and genes in the transient-dark condition.

d. Repeat parts a and b for a comparison of the mean standardized growth of genes in the transient-light condition and genes in the transient-dark condition.