Post embryonic development and cancer Flashcards
Growth is a key factor to determine what?
Shape
How does most growth occur?
Proliferation = hyperplasia
Cell enlargement = hypertrophy
Accretion
What is accretion?
Gradual accumulation of layers/matter
Which cyclins control which cdks?
A/B = Cdk1 D = Cdk 4/6 E = Cdk 2 A = Cdk 2
Describe the cell cycle of nuclei in the syncitium
Very rapid cylces of S and M phases only, no G phases
At which cycle is G2 introduced?
14
What happens to nuclei when they migrate to the periphary?
Cellularisation occurs as a result of the membrane involuting
The AP and DV axis can affect division in what way?
Position can affect the cells division rate
Cells form mitotic domains
What is the role of string?
It is a phospatase that activates the Cdks
Describe the distribution of string in divisions 1 to 13, and then afterwards
In 1 - 13 it is evenly ditributed = rapid and synchronous division
After it is under control of the patterning genes which set up the AP or DV axis
Name the only exception where string does not have the expected effect and why this is
The mesoderm - one of the first to express string but it is the 10th to divide
This is due to trubble which inhibits string
It is inhibited as mesoderm needs to invaginate - cell division would inhibit this
Describe what happens if a limb bud is taken from a large animal and transplanted to a smaller one
The limb would grow to the size of the original limb bud from the bigger animal
What happens if additional thymus glands are transplanted?
They all maintain their size and multiple amounts of tissue is made
Describe the inactivation of the Hippo pathway
Inactive = transcription factor Yki/Yap/Taz in the nucleus is stimulating growth
What happens when the Hippo pathway is active?
The transcription factors are excluded from the nucleus stopping further growth
What may active the hippo pathway?
Cell to cell contact eg overcrowding
What happens if hippo is mutated?
The pathway is inactivated = innapropriate growth
eg mice overall size is the same but the liver is not
Why do pygmies have a short stature?
They do not undergo a second growth rate in puberty
In drosophila, what determines the size of the adult fly?
The size of the larva
What determines the size of the larva?
By insulin signalling - this affects both the duration and rate of larval growth
What induces metamorphis?
Ecdyson
Which pathways may be responsible for determing the size of different dog breeds?
IGF and GH
Where is growth hormone produced?
In the pituitary
What stimulates growth hormone release and what inhibits it?
Stimulate = growth hormone releasing hormone
Inhibit = somatostatin
Both come from the hypothalamus
How can a mother influence growth?
The enviroment of the wound
How can maternal conditions affect life postembryonically?
Inadequate growth in uterus due to a diet can lead to life long consequences
The embryo may catch up in growth but effects still seen eg obesity, diabetes and CHD later on in life
Where are cancers most commonly found?
In tissues that continously divide through life eg epithelia and blood
What is a teratoma?
Cells similar to embryonic cells which can give rise to all three germ layers
They form a tumour made up of many different cell types
What are protooncogenes called if their activated?
oncogenes
List examples of protooncogenes
Ras
Raf
Epidermal growth factor receptor
Myc
List examples of tumour suppressor genes
Retinoblastoma p53 Patched Adenomatous polyposis coli Von Hippel Lindou
How is molting and metamorphis coordinated?
Influences from the enviroment that act on the CNS
Why do Arthropods have to molt?
To grow - their cuticle is rigid so they have to molt
This is called ecdysis
Molting is initiated by what?
The activation of stretch receptors in the cuticle
This releases protothoracicotrophic hormone
Where does protothoracicotopic hormone come from?
The corpus alatum
Which hormone causes molting?
Ecdyson
How does a new cuticle form?
The free epidermal cells proliferate and secrete a fluid to form a barrier
They then start secreting a new cuticle
Then the old cuticle will shed
Metamorphis occurs under the influence of what in insects?
Nutrition, temp and light
Which hormones prevent metamorphis?
Juvenile hormones
What is the effect of thyroxin on the limbs and tail in frogs?
Growth of limbs and degeneration of tail
