Lecture 6 - Development Flashcards
Cell Differentiation
The process of unspecialized cells becoming distinct cell types, e.g. neurouns, muscle cells, blood cells, etc
Mechanisms of cell differentiation:
cytoplasmic determinants, induction
Cytoplasmic determinants
Regulatory molecules are unequally distributed to daughter cells
Induction
One daughter cell receives an extracellular signal that the others do not
Cell differentiation signals come from:
extra-embryonic development (eg. gravity in the egg/womb needed for development of a chick), or from other cells (ex. neuron development)
Cytoplasmic determinants occur in:
Simple animals with very few cells, where the loss of cells leads to the loss of body parts
Induction occurs in:
Complex animals with many cells, as embryos can compensate for the loss of a single cell
Developmental mechanisms control:
which cells in the embryo divide, when they divide, how many times they divide
Signaling molecules are
Usually proteins
Ligand
Binds to the receptor, and may be secreted
Receptor
Can be inside of or on the surface of the cell
Lateral inhibition
An example of cell-cell interaction; that determines which cells will become neurons. It involves signaling from cells, that reduces signaling from neighboring cells to compete to become a neuron. Only one cell wins and becomes a neuron
Gastrulation
A form of cell movement that positions the germ layers (endoderm, ectoderm, mesoderm) to develop into bodily systems
Neural tube development
A form of cell shape change forming the embryonic structure that ultimately forms the brain and spinal cord
Apoptosis
A highly regulated series of events that lead to the death of a cell
Central dogma
In differential gene expression, the changing from DNA to mRNA to a protein. All cells in the organism have the same DNA but form into different cell types (eg. muscles, neurons, etc.0
Transcription factor
A protein that binds to DNA and recruits (activates) or blocks (represses) RNA polymerase. Different cell types express different transcription factors which stops them from being a different cell type (Ex. neural protein is expressed but muscle protein isn’t)
Body plan patterning - flies
Segments of the fly arranged in anterior-posterior order, with three tagmata (functionally integrated groups of segments) formed that become separate organs, one for head, another for thorax, another from abdomen
Bicoid
The transcription pattern allowing for formation of the anteroposterior axis, with high levels of bicoid in one part causing a part of a body to be more anterior, and with low levels of bicoid causing it to be more posterior. When a fruit fly does not express bicoid, posterior structures will be on both the anterior and posterior parts of the animal
Morphogen
A concentration gradient providing spatial information to embryonic cells
Eyeless gene (ey) in fruit flies
(ey) codes for a transcription factor expressed in the developing eye, causing eyes to occur only in the area where eyes should be, if it is lost it can lead to loss of eyes, if it is misexpressed it can cause ectopic eyes (eyes in the wrong place such as on the leg)
Hox genes
Can specify segment identity (ex. wings on the second thoracic segment and halteres on the third thoracic segment). Each Hox gene has its own expression pattern and specifies unique segment morphology
