BIOL103 GENETICS AND DEVELOPMENT LECTURE 5 STUDY GUIDEVivian Irish

Concepts to know (terms to know and be able to use are underlined):

You should be able to diagram a gene and the important facets of its architecture; including promoter, cis-regulatory (or enhancer) sequences, coding region, 5 untranslated region (5 UTR), 3 untranslated region (3 UTR).

Homeotic genes specify segmental or regional identity; homeotic gene products act in combination to specify these identities (in a process often described as a combinatorial code). Homeotic genes are generally expressed in domains larger than one segment or one region, but it is the combination of homeotic gene functions that can uniquely specify an identity. You can think of this code like a zip code. Homeotic genes encode transcription factors that specify these regional identities by binding to the regulatory regions of genes and turning them on or off in particular regions of the body.

You should understand the concept of necessary and sufficient as they pertain to gene function, and how to test for necessity and sufficiency. You should understand the concept of rescue experiments, ectopic expression experiments, loss of function, and gain of function.

You should understand that gene sequences can be conserved, and that gene functions can be conserved, and understand the distinction between these two concepts.

You should understand the distinction between cytoplasmic determinants (that can be asymmetrically apportioned to daughter cells, resulting in differences in daughter cell gene expression) and induction (whereby one group of cells produced an extracellular signal that impacts the fate of neighboring cells, resulting in differences in cell fate).

Induction is frequently accomplished by one cell producing an extracellular ligand that binds to a receptor on a neighboring cell. Binding of the ligand to the receptor initiates a signal transduction cascade in the receiving cell that culminates in changes in gene expression.

Early animal development starts with fertilization, followed by cleavage of the fertilized zygote. Cleavage produces a hollow ball of cells called the blastula (or blastocyst in mammals). Cells in the blastula then rearrange during the process of gastrulation to produce three germ layers; the ectoderm, mesoderm, and endoderm.

Following gastrulation, neurulation (initiation of the nervous system) occurs (in vertebrates). Organogenesis (the formation of organ systems) follows neurulation. The movements of cells during these processes results in cells having new neighbors, which then can allow for new inductive interactions to occur.