Totipotent cells are stem cells that can differentiate into any cell type. These cells are interesting because the way that they differentiate is very understood and could lead to breakthroughs in stem cell technology and therapies

Cell differentiation

Pattern formation is the development of spacial organization and specialization of cells

They're programmed chances in cells themselves

Positional information is involved in cell signaling. Positional information could involve things like cell division factors among other things

Each haploid will be either a or alpha (but not both). Diploid cells will contain both the a and the alpha and in tetrad spores both types will be present in a 1:1 ratio

The MAT locus controls the a and alpha mating types. It encodes the mating type transcriptional regulators

"A" haploid cells express a-specific genes, alpha hploid cells express alpha-specific genes and both types express haploid specific genes

A1 is found in A cells, alpha-1 and alpha-2 are expressed in alpha cells, Mcm1 is expressed in both and HO endonuclease (which is a mating type conversion factor) which acts as a RME1 repressor for meiosis-specific genes

A1 and Mcm1 are expressed. A1 has not regulatory activity by itself and Mcm1 positively regulates aSG expression (the meiosis-specific product). Due to the haploid nature of the cell the haploid-specific genes are turned on as the default

Alpha-1, alpha-2 and Mcm1 are all expressed. Mcm1 and alpha-1 positively regulate alpha-SG expression but Mcm1 and alpha-2 turn off aSG expression. Haploid-specific genes are turned on as the default

All genes (a1, alpha-1, alpha-2 and Mcm1) are expressed. Mcm1 and alpha-2 turn off aSG expression. A1 and alpha-2 turn off hSG and alpha-1 expression. Under normal conditions hSG (haploid specific genes) are expressed as default

C. elegans can be either male or hermaphrodite. Males only produce sperm while hermaphrodites produce both eggs and sperm (and therefore can self-fertilize themselves if necessary)

The uppercase letter denotes the individual from which the cell linage is from. An "a" or a "p" denote anterior and posterior respectively in regards to the positioning of the daughter cells on the C. elegans individual. A.aa results in apoptosis while A.pa, A.ap and A.pp all result in viable individuals

Recessive mutations result in a loss of function (either the tRNA isn't produced or the protein itself is inactive) whereas dominant mutations result in a gain of fuction (the gene is over-expressed or expressed at the wrong time)

Normally Z1-ppp differentiates into an anchor cell and Z4-aaa differentiates into a ventral uterine cell (or the other way around). If either cell is knocked out the other cell will differentiate into an anchor cell. In a recessive LIN-12 mutation the cells will differentiate into anchor cells, if dominant the cells will become ventral uterine.

The LAG-2 gene encodes for the signaling ligand (protein) whereas LIN-12 is the receptor. When one cell produces enough of the LIN-2 complex it will be determined as the anchor cell and will "win" the battle with any cells around it that don't product as much LAG-2

The default state is AC. VU cells need to be specifically "told" by stronger LAG-2 expression to not be the anchor cell

It passes down the LIN-3 ligand to determine where it should be (DON'T confuse LIN-3 and LIN-12!)

That cell will produce the primary vulval cells

A mutation there could result in abnormal vulval development such as the complete lack of vulval (resulting in the "bag of worms" phenotype where the parent C. elegans will explode like the infected host cell of a virus

Multiple vulva can form within an affected C. elegans individual

Epistatic interactions can occur which can define signaling and development pathways. Switch regulation pathways can stimulate or inhibit the activity of the next component in the pathway and within caveats the mutants must be in the same pathway and result from lass of function alleles

Epistasis is determined by how contrasting mutant phenotypes effect each other. Mutant A causes vulvaless individuals while mutant B causes multi-vulva individuals. When A and B are mixed the individuals are vulvaless. The epistatic gene is the mutant phenotype that masks the other while the the hypostatic gene is the mutant that is masked. Epistatic genes act downstream of their hypostatic precursors

An epistatic gene is a mutant phenotype which masks the other mutant phenotype which may be present

A hypostatic gene is the trait which is masked in the case of epistasis

Epistatic genes are downstream from hypostatic genes

If one gene results in the same phenotype in the presense of differing alleles of another gene then the gene that is constant is the epistatic gene and the other is hypostatic