The cascade continues as this gradient of gene expression results in further differentiation and specialization of the body segments. Homeotic genes are master controls that function during embryonic development in animals to determine the developmental fates of different groups of cells destined to become different tissues. Their improper functioning can lead to bizarre changes in morphology B. Signal-transduction pathways convert messages received at the cell surface into responses within the cell 1. The gene expression of one cell can affect the gene expression of other cells. This is the result of signal-transduction pathways.
Signal transduction plays a major role in the regulation of the cell cycle.
The importance of signal-transduction pathways is also shown in the discussions of cancer and control systems 2. C. Key developmental genes are very ancient 1. Virtually every homeotic gene found in fruit flies contains a common 180- nucleotide sequence . Very similar sequences have been found in virtually all eukaryotic organisms studied. These organisms range from unicellular organisms such as yeast to plants, earthworms, frogs, chickens, mice, and humans.