Essential Knowledge 2.E.1

Timing and coordination of specific events are necessary for the normal development of an organism, and these events are regulated by a variety of mechanisms.

Observable cell differentiation results from the expression of genes for tissue-specific proteins.

Induction of transcription factors during development results in sequential gene expression. Homeotic genes are involved in developmental patterns and sequences. Embryonic induction in development results in the correct timing of events. Temperature and the availability of water determine seed germination in most plants. Genetic mutations can result in abnormal development. Genetic transplantation experiments support the link between gene expression and normal development. Genetic regulation by microRNAs plays an important role in the development of organisms and the control of cellular functions.

Programmed cell death (apoptosis) plays a role in the normal development and differentiation.

Examples:

• Morphogenesis of fingers and toes
• Immune function
• C. elegans development
• Flower development

Students should be able to:

LO 2.31 Connect concepts in and across domains to show that timing and coordination of specific events are necessary for normal development in an organism and that these events are regulated by multiple mechanisms.

LO 2.32 Use a graph or diagram to analyze situations or solve problems (quantitatively or qualitatively) that involve timing and coordination of events necessary for normal development in an organism.

LO 2.33 Justify scientific claims with scientific evidence to show that timing and coordination of several events are necessary for normal development in an organism and that these events are regulated by multiple mechanisms.

LO 2.34 Describe the role of programmed cell death in development and differentiation, the reuse of molecules, and the maintenance ofdynamic homeostasis.