L2 Invertebrate Models Sea Urchin and C. Elegans (Imported from Quizlet)

Sea urchins have a large number of what? To be used for?

Large number of embryos for experimental manipulation

Genetic models, here breeding is easily done in a lab. Genes within the genome can be altered to study what?

Their effect on development

What is the other name for fruit flies?

Drosophila melanogaster

Sea urchins are ...?

Echinoderms

Echinoderms are what?

Deuterostomes

What is meant by deuterostome?

Mouth forms first

Sea urchins have transparent embryo which is large and easily accessible for manipulations -> you can see right through them and what can be followed live under a microscope?

Gastrulation

What is the life cycle of a sea urchin?

In about 4 hours it develops into a blastula through a number of stereotypic cell divisions -> this means they have a strict order and orientation

What happens onwards from the first day in sea urchins?

Gastrulation

Movements during which the primitive gut is formed, this fuses at the ______ side forming a mouth (deuterostome), the larva has an internal _______ skeleton that is responsible for these _______ on the ______ larva

Animal, calcareous, extensions, pluteus

Sea urchin experiments contributed to discussion on two types of development, what are these?

Mosaic, regulative

Mosaic model (Weissman)

A variant of this is where cytoplasmic determinant control cell fate by specific segregation to these cells a variant of this model would be one where cytoplasmic determinants specify fate

Regulative development

Differences can be generated de novo by cell-cell interactions

What is happening in this image?

The first two cleavages are perpendicular but parallel to the animal vegetal axis of the egg

The animal vegetal axis is an asymmetry in the egg that can already be observed at fertilisation when the zygote is formed

The vegetal pole is shown in red here and is the place where gastrulation will always occur

The third cleavage is again perpendicular to the other two cleavages and separates 4 animal cells from 4 vegetal cells

If determinants were present one would get a normal embryo, from a single blastomere Hans Driesch showed that in the sea urchin development can be ______ -> because when he separated the two blastomeres at the 2 cell stage he did not get _ _____ _____ rather he got two smaller but complete embryos thus the cells had adapted their ______ _______ _______

Regulative, 2 half embryos, normal developmental programmes

What is the conclusion fro Hans Driesch's experiment?

Development is regulative rather than mosaic

Splitting the 8 cell embryo in a ventral and dorsal half showed what?

That there is at least along this axis a degree of mosaicism is present, in such a case normal embryos are not formed

What is formed rather than normal embryos in splitting the 8 cell embryo?

An animalized and vegetalised incomplete larvae are the result, thus when we consider this axis there appears to be some form of mosaicism

Localised determinants for this are in the ______ rather than the ______

Cytoplasm, nucleus

What are the ideal characteristics of C. elegans for ease of genetic analysis?

Small organisms (because of the need to keep large numbers), easy to breed, large batches of embryos, easy scoring of phenotypes, short generation time, sequenced genome

C. elegans mainly consist of a gut and reproductive organ with muscles to move and has neurone and sensory cells that do what?

Convey information to the animal about the environment it's navigating

C. elegans develop really rapidly and hatches from the egg within ____ hours at normal temperatures

24

C. elegans usually develops as a hermaphrodite, what is meant by this?

It will first become a male and then transform into a female that can use her own sperm to fertilise the eggs

Occasionally "male only" individuals of C. elegans will occur, what will they do?

Mate with females

In this way, continuous inbreeding which would be ______ for their fitness is _______

Detrimental, prevented

In stereotypic cleavage patterns, the first cell divides to form the __ and ___ cell whereas the AB cell forms ____ and ____

P2, EMS, ABP, ABA

A is _____, P is _____

Anterior, posterior

C. elegans have a completely _______ cell division pattern, the fate of each of the early cells can therefore be _______ precisely

Stereotypic, mapped

The AB cell mainly makes ______ and _______

Hypodermis, neurons

EMS cell predominantly (not perfectly) makes ______ and ______

Mesoderm, endoderm

The C and D cells (formed from P2 and P3 respectively) will also make ______ _____

Somatic tissue

P4 will go on and form ___ _____ _____

The germ line

P4 receives _______ ______ named _-_______

Cytoplasmic granules, p-granules

Although the lineage is invariant, cell fate is not absolutely determined. What can change fate?

Experimental manipulation

The first cleavage is asymmetric due to the action of a set of ...?

Par proteins (par from partitioning)

One of these Par genes acts in another invertebrate model, but in another cellular context, which model is this?

Drosophila

In this image, what is happening?

The relative position of the cells is changed by simply prodding the cells -> this can lead to the ABA cell lying posterior and the ABP lying anterior

These will then go on to produce the lineage according to their new position, this would be impossible if they would contain determinants

The EMS cell is formed by what originally would have been the P2 cell -> so also here there is no fixed determinant

C. elegans are made of ____ cells but precisely ___ cells are programmed to die (apoptosis)

1090, 131

What is meant if branches in C. elegans trees end in X?

This denotes this particular cell is programmed to die

In multicellular organisms, cells are sometimes ______ _____ -> this happens during development but it is also essential in a variety of biology processes in adults

Actively removed

Apoptosis is a highly controlled process, not simply bursting of a cell (this is called ______)

Necrosis

As apoptosis occurs in a highly _____ manner in C. elegans, it allowed an ______ _____ ______ of the process in this organism

Stereotyped, efficient genetic dissection

In C. elegans, the pathway/genes required for this process (apoptosis) were first identified using ____ then ______ because this process is highly stereotypic it allowed a ______ _____ ______ of the process in this organism, first by identifying mutations in C. elegans that disrupt proper apoptosis

Genetics, molecularly, systematic genetic dissection

The genes that were disrupted by these mutations in C. elegans were identified molecularly, what did this lead to?

Outline of a pathway that leads to apoptosis

What is essential for proper development?

Formation of reproductive organs male/female, skin between digits, immune system maturation

What is essential for homeostasis?

Mitosis/apoptosis to maintain constant number of cells, removal of damaged cells (DNA damage, viral infections)

Improper regulation of apoptosis can lead to disease, what are these diseases?

Autoimmune disease, cancer

What is BID?

BH3 interacting domain death agonist

What is BCI2?

B-cell lymphoma 2

What is APAF1?

Apoptotic protease activating factor 1

What is a caspase?

Cysteine-aspartate protease

What does this image illustrate?

How C. elegans pathway allowed identification of homologous pathways and genes in vertebrates

What is RNAi?

RNA interference

What is RNA interference?

A powerful mechanisms to control the flow of genetic information during development

Double stranded RNA triggers a _________ process that ______ or _______ translation identical mRNAs

Biochemical, degrades, blocks

What is RNAi able to control expression of?

Genes after transcription has taken place, this pathway was to a larger degree worked out in C. elegans

What libraries were targeting every gene in the genome (humans and C. elegans)

Genome-wide siRNA libraries

This double stranded RNA can be taken up by certain cells and ______ and cut into smaller pieces by an enzyme named ____ creating short interfering RNAs (siRNAs)

Recognised, dicer

These siRNAs are loads into a protein complex named ____ which uses the siRNA sequence to find mRNAs that are _____ to the siRNA and causes their _______

RISC, complementary, degradation

The fact that short RNAs are used is important, why?

As such oligos can be synthesised chemically

RNAi has allowed the creation of siRNA libraries that do what?

Target every gene in the human and C. elegans genomes

RNAi is used in research, what kind?

Acute down regulation of gene expression in C. elegans and cell culture

RNAi acts to do what?

Downregulate the activity of these faulty genes

What does this image show?

RNAi mechanism