What Controls Development?

Question 1

What controls development?

Answer 1

Cytoplasm

Genes

External environment

Question 2

What was the Spemann Experiment?

Answer 2

Cut two salamander zygotes differently

If both segments got some gray crescent, both develop into fully formed adults

If only one segment gets the gray crescent then only the one with it turns into a fully formed adult

Conclusion = cytoplasmic factors in gray crescent are necessary for development

Question 3

What is genomic activation?

Answer 3

The transition from maternal control to embryonic control

Timing varies by taxa

Question 4

What is genomic equivalence?

Answer 4

No information is lost in early stages of embryonic development

Question 5

What is cytoplasmic segregation?

Answer 5

Dividing cells receive unequal amount of material that were distributed unevenly in the zygote

Question 6

What causes cell differentiation?

Answer 6

More material at vegetal pole

Bottom cells would give different signals than the top ones

Question 7

What is primary induction in amphibians?

Answer 7

Cells moving over dorsal lip of the blastopore (Spemannn Organiser)

Induces overlaying ectoderm to form neural tissue

Question 8

What is primary induction in birds?

Answer 8

Cells moving over Henson’s node are induced to form CNS

Question 9

What is secondary induction in vertebrate eye?

Answer 9

Forebrain bulges out to form optic vesicles

Signals from vesicles induce surface tissue to form lens placo tissue

Tissue gives rise to sensory organs

Tissue differentiates into lens

As it differentiates it influences optic cup and cornea formation

Question 10

What makes something a morphogen?

Answer 10

Directly affects target cells

Different concentrations cause different effects

Question 11

What causes positional information?

Answer 11

Given by the concentration gradient of a morphogen

Question 12

What genes establish body segmentation and how?

Answer 12

Gap genes = organise large areas along anterior-posterior axis

Pair rule genes = divide embryo into units of two segments each

Segment polarity genes = determine segment boundaries

Homeotic genes = expressed along length of the body and determine what segments will become

Question 13

What do segmentation genes influence?

Answer 13

Number, boundaries and polarity of body segments

Question 14

What do Hox genes control?

Answer 14

Control differentiation along body axis

Question 15

Where is Hoxb1 expressed?

Answer 15

Anterior part of the hindbrain

Question 16

How are Hox genes expressed?

Answer 16

First Hox gene expressed most anterior and last gene expressed most posterior

Question 17

What is antennapedia?

Answer 17

Legs grow instead of antennae

Question 18

What is bithorax?

Answer 18

Extra thorax so has two sets of wings

Question 19

What causes spina bifida?

Answer 19

Failure to close at posterior end during neurulation

Question 20

What causes anencephaly?

Answer 20

Failure to close at anterior end during neurulation

Question 21

What does lack of iodine cause?

Answer 21

Goitre in adults

Cretinism in babies

Question 22

How many somatic cells are programmed to die in C.elegans

Answer 22

131

Question 23

What stimulates apoptosis between human fingers and toes?

Answer 23

Capsase enzyme

Question 24

What is genomic imprinting?

Answer 24

Some development genes are only active if they come from sperm, others from eggs

Question 25

What do female genes control?

Answer 25

Embryo

Question 26

What do male genes control?

Answer 26

Trophoblasts and the placenta

Question 27

How do limbs develop?

Answer 27

Develop from limb bud

Cells receive positional information then organise appropriately

Cells at the base of the limb bud make the morphogen BMP2

BMP2 gradient determines anterior-posterior limb axis

Highest BMP2 dose = thumb

Smallest BMP2 dose = little finger