Lecture 6 - Development

Question 1

Cell Differentiation

Answer 1

The process of unspecialized cells becoming distinct cell types, e.g. neurouns, muscle cells, blood cells, etc

Question 2

Mechanisms of cell differentiation:

Answer 2

cytoplasmic determinants, induction

Question 3

Cytoplasmic determinants

Answer 3

Regulatory molecules are unequally distributed to daughter cells

Question 4

Induction

Answer 4

One daughter cell receives an extracellular signal that the others do not

Question 5

Cell differentiation signals come from:

Answer 5

extra-embryonic development (eg. gravity in the egg/womb needed for development of a chick), or from other cells (ex. neuron development)

Question 6

Cytoplasmic determinants occur in:

Answer 6

Simple animals with very few cells, where the loss of cells leads to the loss of body parts

Question 7

Induction occurs in:

Answer 7

Complex animals with many cells, as embryos can compensate for the loss of a single cell

Question 8

Developmental mechanisms control:

Answer 8

which cells in the embryo divide, when they divide, how many times they divide

Question 9

Signaling molecules are

Answer 9

Usually proteins

Question 10

Ligand

Answer 10

Binds to the receptor, and may be secreted

Question 11

Receptor

Answer 11

Can be inside of or on the surface of the cell

Question 12

Lateral inhibition

Answer 12

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

Question 13

Gastrulation

Answer 13

A form of cell movement that positions the germ layers (endoderm, ectoderm, mesoderm) to develop into bodily systems

Question 14

Neural tube development

Answer 14

A form of cell shape change forming the embryonic structure that ultimately forms the brain and spinal cord

Question 15

Apoptosis

Answer 15

A highly regulated series of events that lead to the death of a cell

Question 16

Central dogma

Answer 16

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

Question 17

Transcription factor

Answer 17

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)

Question 18

Body plan patterning - flies

Answer 18

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

Question 19

Bicoid

Answer 19

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

Question 20

Morphogen

Answer 20

A concentration gradient providing spatial information to embryonic cells

Question 21

Eyeless gene (ey) in fruit flies

Answer 21

(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)

Question 22

Hox genes

Answer 22

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