embryology and inductive signals - lecture 9

Question 1

What do transcription factors do?

Answer 1

Bind to the DNA , stimulating gene expression. Determine cell fates by being activated at different points in development

Question 2

What are inductive signals?

Answer 2

messengers/signals which activate different transcription factors

Question 3

How do the concentrations of the inductive signals change?

Answer 3

Further from the signalling cells produce inductive signals , induce lower concentration of the signal

Question 4

What is the actual mechanism of inductive signals

Answer 4

Receptors span the plasma membrane.

Protein enters nucleus and activates the transcription , to activate transcription of the genes.

Question 5

What is a homeotic gene?

Answer 5

ny of a group of genes that control the pattern of body formation during early embryonic development of organisms

Question 6

What happens when you separate an fertilised embryo , but both contain a grey crescent?

Answer 6

Normal development

Question 7

What happens when the grey crescent isn’t present?

Answer 7

Only a belly piece develop

Question 8

What happened when a dorsal lip is cut out and transferred to the ventral half of another embryo?

Answer 8

Resulted in a two headed embryo. Therefore the dorsal lip is responsible for the spinal region

Question 9

Who was given the noble prize for discovery of the function of the spemann

Answer 9

Hans Spemann

Hilde Mangold

Question 10

What change in fate does the Spemann organiser graft make?

Answer 10

It induces a Dorsal fate in cells that would otherwise follow a ventral fate. Forms a backbone instead of belly

Question 11

How can you find the gene responsible for different embryological growth?

Answer 11

Make a plasmid library. Inject mRNA into the embryo, lots of protein is then made by the mRNA.Does this alter protein development

Question 12

Why is UV used to inhibit dorsal structures?

Answer 12

Then lots of different mRNAS were injected to find one which rescued head development

Question 13

What is Noggin?

Answer 13

Secreted signalling molecule that can promote dorsal structures

Question 14

What is the correct amount of Noggin for normal development

Answer 14

Low concentrations

Question 15

How to find where the gene is expressed?

Answer 15

• Fix the embryos
• RNA probe added which binds to floating mRNA
• Antibody (labelled with an enzyme) binds to a RNA complex
• Embryos washed , antibody has an enzyme attached which allows for production of a coloured ppt

This is called in situ hybridisation

Question 16

Where is noggin expressed?

Answer 16

In the Spemann organiser

Question 17

What fates do cells far form the Spemann organiser follow?

Answer 17

ventral fate . Cells close follow dorsal fates

Question 18

What happened in Hans Spemann and Hilde Mangold experiments?

Answer 18

• removed the Spemann organiser (dorsal lip) which forms on the side of the embryo which will give rise to the dorsal side - the side with the brain and spinal chord
• grafted to the ventral side
• made an embryo with an extra head and spinal chord

Question 19

How was Noggin identified as an inductive signal/ inducing factor?

Answer 19

• plasmid library was made which has many random genes
• Each plasmid was used to make mRNA
• Each mRNA was injected into separate Xenopus laevis embryos , in order to make the proteins that the RNA codes for
• some embryos treated with UV to lose their dorsal structures
• RNA injected into these embryos that promotes dorsal structure again , ended up being noggin

Question 20

What role does signal transduction play?

Answer 20

relays the ‘message; from the extracellular signal from the membrane to the nucleus where it activates gene expression via a transcription factor

Question 21

What is the Spemann organiser the same thing as?

Answer 21

the dorsal lip