Control of development

Question 1

What are the key stages of developement?

Answer 1

Fertilisation
cleavage
gastrulation
organogenesis
morphogenesis

Question 2

What controls developement?

Answer 2

cytoplasm
genes
external environment

Question 3

What does Nuclear DNA usually do that doesn’t occur in early developement?

Answer 3

Makes proteins by transcription, in early developement it only replicates

Question 4

Where do proteins and enzymes come from in early development?

Answer 4

Provided for by the cytoplasm

Question 5

Where does zygotic cytoplasm come from?

Answer 5

The mother, so early development under maternal control

Question 6

What is genomic activation?

Answer 6

The transition from maternal control to embryo control

Question 7

Timing of genomic activation varies among species, when does it occur for:
pigs?
humans?
frogs?

Answer 7

Pigs = in 4-8 cell embryo 
Humans = 8 cell embryo
Frogs = 3000-4000 cell embryo

Question 8

What are cells called prior to determination?

Answer 8

Totipotent

Question 9

What causes differentiation to occur?

Answer 9

results from differential gene expression, which is influenced by the cytoplasm and extracellular environment

Question 10

What is genomic equivalence?

Answer 10

Each cell in the body has same genetic material and therefore all the information necessary to create a complete organism

Question 11

What controls the fate of the nucleus?

Answer 11

The cytoplasm

Question 12

What is cytoplasmic segregation?

Answer 12

Occurs in division. Dividing cells receive a factor that is unequally distributed in the cytoplasm and ends up in some daughter cells but not others, causes differentiation on cells

Question 13

What is induction?

Answer 13

A factor is secreted by some cells to induce other cells to differentiate

Question 14

What are the processes of primary induction amphibians?

Answer 14

Cells moving over the dorsal lip of the blastopore (Spemann organiser) induce overlying ectoderm to form neural tissue

Question 15

What are the processes of primary induction in birds?

Answer 15

Cells moving over Hensen’s node are induced to form the Central Nervous System

Question 16

What is secondary induction?

Answer 16

Occurs after primary, includes the development of control in the vertebrate eye

Question 17

What is a morphogen?

Answer 17

A chemical agent able to cause or determine morphogenesis

Question 18

When is a signal called a morphogen?

Answer 18

When it directly affects a target cell or when different concentration cause different effects

Question 19

Describe the process of limb formation

Answer 19

The cells that become the bones and muscles of a limb receive positional information, then organise appropriately. Cells at the bud make the morphogen BMP2

Question 20

how does BMP2 control limb developement?

Answer 20

The gradient determines anterior-posterior axis, A high dose lead to thumbs, a low dose leads to the little finger

Question 21

What is genomic imprinting?

Answer 21

Some genes are only active if they come from the sperm, some are only active if they come from the egg, which means male/male or female/female zygotes can’t form

Question 22

What is Prader-Willi syndrome?

Answer 22

Deletion on the paternal chromosome 15

Question 23

What is angelman syndrome?

Answer 23

Deletion on the maternal chromosome 15

Question 24

What do segmentation genes do?

Answer 24

influence the number, boundaries and polarity of body segments

Question 25

What do gap genes do?

Answer 25

Organise large areas along the anterior-posterior axis

Question 26

What do pair rule genes do?

Answer 26

Divide the embryo into units of two segments each

Question 27

What do segment polarity genes do?

Answer 27

determine segment boundaries

Question 28

What do homeotic genes do?

Answer 28

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

Question 29

What are hox genes?

Answer 29

A subset of homeotic genes that control the body plan of an embryo along the head-tail axis

Question 30

What apoptosis?

Answer 30

Programmed cell death, cause by the activation of ‘death’ genes

Question 31

How does the environment affect developement in house mice?

Answer 31

Gut bacteria induce gene expression in the intestine, which is essential for normal capillary development

Question 32

What happens in humans as a result of neural tube failing to close?

Answer 32

At the posterior = spina bifida

At the anterior = anencephaly

Question 33

What causes goitre and cretinism?

Answer 33

Lack of iodine in the diet

Question 34

What does Cyclopamine cause?

Answer 34

Birth defects in lambs, found in corn lily plants, inhibits action of the sonic hedgehog protein which is involved in neural system formation