12 - Genetics of Development

Question 1

Determination

Answer 1

the process that leads up to the observable differentiation of a cell

Question 2

How is a determined cell different from a differentiated cell?

Answer 2

A determined cell has the master regulatory genes turned on, but not the cell-specific genes and does not have the physical appearance of the specific cell type, where as a differentiated cell has both master regulatory and cell- specific genes turned on and has the appearance of the specific cell

Question 3

Describe the process of determination of muscle cells

Answer 3

Signals from other cells result in the activation of the myoD master regulatory gene which results in the production of the MyoD transcription factor.
The cells are now myoblasts

Question 4

Describe the process of differentiation of muscle cells

Answer 4

MyoD activates the expressions of other muscle specific transcription factors which results in the activation of genes for the production of specific proteins (such as myosin) and the prevention of cell division which allows the myoblasts to form muscle fibres

Question 5

Three main phases of Drosophila development

Answer 5

I. Establishing the main axes
II. Establishing the segments: head, thorax, abdomen
III. Filling in the details – i.e. building the various organs of the animal (wings, legs, and eyes etc.)

Question 6

What are egg polarity genes?

Answer 6

Genes that determine the polarity of the egg (I.e. where the head and tail are) by encoding for transcription factors

Question 7

How does the Bicoid protein provide positional information along the anterior-posterior axis of the fly embryo?

Answer 7

It is a gradient, with high concentrations at the anterior end and low concentrations at the posterior end which results in a higher rate of transcription of bicoid mRNA at the anterior end

Question 8

What are the three types of segmentation genes?

Answer 8

gap genes, pair-rule genes, segment polarity genes

Question 9

What do gap genes do?

Answer 9

divide embryo into broad segments and induce pair-rule genes

Question 10

What do pair rule genes do?

Answer 10

establish pairs of segments and induce segment polarity genes

Question 11

establish pairs of segments and induce segment polarity genes

Answer 11

establish anterior-posterior gradient within each segment and induce homeotic genes

Question 12

What are homeotic genes?

Answer 12

regulatory genes that determine the location and organization of body parts

Question 13

Hox genes

Answer 13

encode transcription factors with a conserved DNA binding domain (the ‘homeobox’ domain)
• Hox genes occur in clusters, arranged in the same order as the regions they affect (‘colinearity’)