Lecture 7B: Mechanisms of Development

Question 1

A gene similar in structure and evolutionary

origin (and likely function) to a gene in another species

Answer 1

Homologous gene

Question 2

What concept is described by, “All cells contain the same set of genes, but different cells express diff sets of genes.” What provides evidence that all cells have identical genetic material?

Answer 2

Genome equivalence. Somatic nuclear transfer.

Question 3

Only a small percentage of the genome is expressed in cell type describes what concept?

Answer 3

Differential gene expression

Question 4

Name levels at which gene expr is regulated at?

Answer 4

•
differential gene transcription
•
selective nuclear RNA processing
•
selective mRNA translation
•
differential protein modification

Question 5

The expression of different sets of genes in different cells coordinates development by controlling four essential cellular processes by which the embryo is constructed. What are they?

Answer 5

Cellular proliferation, specialization, interactions, and movement.

Question 6

Induction

Answer 6

One group of cells changes the behavior of an adjacent group of cells.

Question 7

Name the two components to every inductive interaction

Answer 7

Inducer and responder (responder must be ‘competent’)

Question 8

Competence is actively acquired. What signal makes the ectoderm competent to respond to inductive signals from the optic vesicle?

Answer 8

Pax6

Question 9

By what means of signaling are signals transmitted between inducers and responders?

Answer 9

Juxtacrine and paracrine.

Question 10

Paracrine signaling molecules that cause conc-dependent effects are called? Elaborate on their function?

Answer 10

Morphogens. A morphogen can specify more than one cell type to be directed into a certain developmental pathway by forming a concentration gradient

Question 11

Asymmetric fluid flow in the node establishes a morphogen gradient of what molecule that is asymmetrically expressed on the left side of the node/organizer region? This signal is then relayed to create a broad stripe of its expression in the lateral plate mesoderm along the left side.

Answer 11

Nodal

Question 12

What gene links the outcome of the Nodal/
Lefty (antagonist of Nodal) interactions to subsequent anatomical development? What are the genes involved in that the gene in question is thought to regulate the expression of?

Answer 12

Pitx2. The transcription factor Pitx2 is expressed on the left side of the developing heart, gut and brain. Pitx2 is thought to regulate expression of genes that mediate asymmetric morphogenesis of these organs.

Question 13

The Nodal signaling cascade is involved in what?

Answer 13

Left-Right patterning.

Question 14

What phenomena controls the relay of Nodal asymmetry?

Answer 14

Cell-cell signaling cascade.

Question 15

Autosomal dominant mutations in Pax6 cause [blank]

Answer 15

Aniridia

Question 16

Morphogen gradients pattern the neural tube. Describe their role in D/V patterning.

Answer 16

Bmp/Wnt D to V (from roof plate), Shh V to D (from floor plate).