DEVELOPMENTAL FUNCTION

Question 1

Describe early embryogenesis?

Answer 1

AROUND 3 HOURS:

• nucleus divides in wave of synchronous division as a synctium structure
• nuclei then migrate to peripheries
• TF’s encoded and diffuse as if they are signalling molecules
• embryo cellularises and toolkit genes come on

Question 2

What is a synctium?

Answer 2

a multinucleate structure in a common cytoplasm

Question 3

What did Kathoff (1968) show with his anterior UV radiation attack on the anterior axis of newly fertilised egg? What does this suggest?

Answer 3

• development of two posterior ends

- RNA localises at anterior

Question 4

What is Bicoid?

Where/ when is it found and transcribed?

Answer 4

maternal effect gene whose protein concentration gradient patterns the anterior-posterior axis during Drosophila embryogenesis.

Question 5

What do bicoid mutants show?

Answer 5

normal abdominal dentile patterns but lost all of thoracic and heart segmented units. Instead get more abdominal units

Question 6

What are nurse cells? How are they connected to oocyte?

Are they diploid or haploid? Why is that important?

Answer 6

connected to oocyte by cytoplasmic bridges which supply RNA to egg

DIPLOID- meaning that even if the mother is heterozygous for a mutation she will still produce functioning Bicoid protein

Question 7

What does bicoid associate with?

Answer 7

dyenin

Question 8

Where does bicoid localise?

Answer 8

anterior

Question 9

What does Oskar associate with?

Answer 9

kinesin

Question 10

Where does Oskar localise?

Answer 10

posterior

Question 11

What is the 3’UTR ? How is it used for the embryo to distinguish between bicoid and oskar?

Answer 11

• the untranslated region between a stop codon and the poly A termination site
• bicoid mRNA localisation requires sequences in the 3’-UTR

Question 12

What does it mean for bicoid to be a morphogen ?

Answer 12

different concentrations have differing cellular influences

Question 13

Anterior organiser works by activating genes in zygote, known as __ pattering genes.

Answer 13

AP

Question 14

What activates Huncback?

Answer 14

bicoid

Question 15

What is the difference between Hunchback and Bicoid expression along the AP axis? Why is this the case?

Answer 15

• bicoid is expressed in a gradual gradient along the AP axis
• Hunchback, however, is a much sharper on/off mechanism with sharp localised thresholds

Why? - because hunchback has multiple bicoid binding sites which allow the interaction of bicoid proteins which can shift equilibrium

Question 16

What are gap genes? __ & __ are both examples of gap genes.

Answer 16

• mutants that cause gaps in the phenotye

- Hunchback and OTD

Question 17

What is OTD responsible for coding?

Answer 17

antennae on anterior end

Question 18

Why is OTD expressed in a much narrower region than hunchback?

Answer 18

• because OTD has fewer matching bicoid binding sites, so loads of bicoid must bind in order to trigger transcription, must breach threshold

Question 19

Bicoid has a higher affinity for ____ enhancer DNA binding sites than ____.

Answer 19

Hunchback than OTD