COCKBURN-3 Flashcards
why do the sev (LOF) not die?
they are heterozygous mutants so they have another normal gene
how are P elements used?
keep the inverted repeats
put the transposes on another plasmid
between the inverted repeats but the lac Z reporter gene, and a selection gene that will give a different phenotype (w+ turns white eyes red)
insert the P element into germ cells in the embryos
the germ cells will be in an adult that will give birth to flies with different phenotypes
select the flies that have red eyes (not all flies integrated the P element) and sequence the P element and work with it
what is a gene trap?
interrupts a gene, causing a loss of function
inserts a reporter gene that can be used to visualise where the gene is expressed
combined with genetic screen to combine additional information
the insert relies on the gene promoter and can create a fusion protein
what is an enhancer trap?
the P element has its own promoter and can land anywhere (doesnt have to be inside the gene)
enhancer turns on the gene and the promoter
a way to figure out where enhancers are
used to identify enhancers that promote gene expression in a specific cell type
what do enhancers give
tissue specific control of expression
what are the three ways in which a single cell becomes an organised and functional organism?
cell proliferation, cell differentiation, cell morphogenesis
what are the big steps in the first few days of mammalian development?
fertilisation
major EGA
compaction
cavitation
expansion and hatching
implantation
what happens between fertilisation and the major EGA?
cleavage divisions
the cell divides but does not get bigger
what is the major EGA?
zygotic/embryonic genome activation
up until then the embryo relies on maternal mRNA
after the EGA the cell makes its own mRNA
totipotent
happens around day 4
what is compaction?
the cells become very close together
increase in adherens junctions
prevent water from leaking out during cavitation
what happens during cavitation?
the cell pumps water in
what happens after cavitation
there is loss of totiponcy
cells on the outside form the trophectoderm
the cells inside form the inner cell mass (epiblast and primitive endoderm)
then implantation in the uterine wall happens
how does cell position guide early differentiation?
the cells that form the trophectoderm will form all cell types of the placenta
the cells forming the inner cell mass will become the fetus
how do the cells know what to become?
the cells inside have total cell contact:
have LATS1/2 active which will phosphorylate YAP/WWTR which cannot enter the nucleus and dont activate the Cdx gene (inhibited)
cells with some or no contact inhibit LATS1/2 which allows YAP to enter the nucleus and bind to TEAD4
which will transcribe the Cdx2 gene
LATS1/2 sequestered by F actin
called the hipposignalling pathway
what happens during gastrulation
epiblast undergoes gastrulation
further restricts potency
cells migrate down the primitive streak (site of gastrulation)
the cells that migrate first become the endoderm
the second layer is the mesoderm
the cells that do not migrate become the ectoderm
