Genetics

Question 2

Cell Death

Answer 2

Apoptosis is a normal part of embryo development and may play a role in the following:
* a. Sculpts form
* b. Destruction of vestigial organs
* c. Separation of tissue layers
* d. Creation of lumens

Question 3

Pattern Formation and Morphogenesis

Answer 3

1. Morphogen gradients (a mechanism by which the emission of a signal from one part of an embryo can determine the location, differentiation, and fate of many surrounding cells) establish the major body axes.
2. The sequential activation of genes leads to body segmentation.
3. Segment identity is controlled by homeotic genes (including Hox genes).
   Hox genes (i.e. homeobox-containing genes) are transcription factors that affect cell behavior associated with organ morphogenesis ( the biological process that causes a cell, tissue or organism to develop its shape). The homeobox is a 180nt (60aa) DNA-binding domain.
   Homeosis – Occurs when one body segment takes on the identity of another.

Question 4

Cell Migration

Answer 4

Differentiating cells need to migrate to their proper location in the developing embryo. The ability to modulate adhesion both to other cells as well as to the extracellular matrix is essential.
* Cadherins – Transmembrane proteins that mediate Ca2+-dependent homophilic binding.
* Integrins – Transmembrane proteins used to bind the cytoskeleton to the extracellular matrix. Binding can serve as an anchor but can also activate signal transduction pathways leading to growth of the cytoskeleton or the activation of gene expression.