Midterm 1 Flashcards
A pro-nuclei is
The mothers egg and the father sperm in one egg
Development starts when
the egg and sperm fuse
A zygote is a
single cell
Developmental bio is not a series of phenotypic event but instead
a combo of various processes like using diff cells and tissues to grow
How do you determine the developmental functional of a gene
- Determine where in the embryo the gene is expressed
- Then you can remove the function of the gene (make a knockout)
- Phenotypes
Haploinsufficiency is
when one functional copy of a gene is not enough to provide enough protein for normal funtion
heterozygote loss-oof function mutations cause an
abnormal phenotype when a gene is haploinsufficient
The first clue to the functions of a protein is
where is this gene expresses during development.
What is WISH
A method to tell where in an embryo a given gene is transcribed. (it glows!)
The stages of embryogenesis starts with
fertilization which is the fusion of sperm and egg to produce a zygote
it continues with
cleavage which si rapid mitotic division
Then is
gastrulation which is cell movements that create the three germ layer
followed by
organogenesis which is the tissues and organs form the germ layers
in some species this is followed by the larval stage which is
only in some stuff and sexually immature form that undergoes metamorphosis to become mature
finally is gametogenesis
which is the formation and differentiation of germ cell (starts in the embryo gamtes differentiate in adults)
the front is
anterior
back is
posterior
butt is
dorsal
boobs are
ventral
cutting anterior and posterior is
cross-sectional (transverse plane)
cutting dorsal and ventral is
horizontal (separating boobs and butt)
Embryos are cut through
horizontal so dorsal-ventral
cutting both laterally is
(right down the middle, symmetric) midsaggital
Early cell division is rapid
synchronous cell division during cleavage is followed by asynchronous and relatively slow cell division during gastrulation
Size and volume of the embryo do not significantly increase until
organogenesis has started
So yk how like hundreds of cells divide but!
the size doesn’t increase!!
How do u know organogenesis
as soon as formation of neural tube
A blastomere is any cell
of a cleavage stage embryo
Slide 8 (presentation 2)!
memorize
The beginning of gastrulation is
cells moving inwards
Holoblastic cleavage is
complete so isolecithal or mesoleithal
in holoblastic the cytoplasm is
equally distributed to cells
meroblastic cleaving is
incomplete so telolecithal or centrolecithal
why does the yolk remain separate in meroblastic
cuz its thick and doesn’t allow cell division so yolk remains separate and had no cells
Holoblastic - isolecithal has 4 types explain each
radial cleavage - evenly distributed yolk and spars radial cleavage
spiral cleavage - like a tent with legs
bilateral cleavage - weird circles
rotational cleavage - around a round
holoblastic - Mesolecithal is
displaced radial cleavage so like a globe but slightly off
Meroblastic - telolecithalhas 3 types explain
bilateral cleavege - makes cracks?
discoidal cleavage - fish, reptiles, birds buds pop over
Centolecithal has the
yolk in the center and cells dividing around it
Gastrulation is when
the germ layers are formed and the nervous system is induced
what is the mesodermal structure necessary to induce the nervous system
the formation of the notochord
In vertebrates the notochord
disappears and its not even present in invertebrates
epithelial cells are
attached in a sheet-like form (need to be connected to a neighbour or die)
Mesenchymal cells are
individualized cells and can be individual and motile
Invagination is
making a hollow
Ingression is
the migration of individual cells from the surface to the interior of the embryo (become mesenchymal)
Involution is
inward expansion of cells so it end up covering the internal cells
Delamination is
splitting of a cellular sheet into 2 or more or less parallel sheets. (resembles regression but is actually forming a new epithelial layer)
Epiboly is
several cells layers of cells merging into each other and the entire layers are moving, so it expands and move inwards
Convergent extension
It merges vertically and so grows horizontally
Specification -> _____ -> ______
Determination –> Differentiation
Specification is
when a cell is committed to a certain fate but its still reversible, so it’ll differentiate a certain way unless signal or its environment change
Determination is when
the commitment is irreversible and it’ll happen regardless of its environment if it changes
Differentiation is when
it develops into a specialized into a certain cell type. its a certain type both functionally and biochemically
How do we know a cell is a specified cell
if you put 2 diff cells in the same neutral environment and they both turn into their own diff cell types we know they are specificated
Autonomous specification is when
blastomeres acquire determination factors from egg cytoplasm (the mother supplies the determination?)
Conditional specification is when
embryonic cells are specified by signal from their neighbouring cells
So only in amphibians does
autonomous specification starts from a zygote
Fate maps of vertebrates refer to
a cells future path of differentiation like a statistical likelihood
In an autonomous manner at the “8-cell stage”
its already determined
Even our first two cells contribute
unequally to the human embryo therefore specifies
A syncytium is only present in insects and
is a cytoplasm containing many nuclei, the cell membrane haven’t formed between nuclei (double check)
A morphogen is a
long-range signalling molecule that forms a concentration gradient in the embryo and so the specification/determinations depends on the concentration of the molecule.
In contrast a determinant influences cell fate
in the cell where it is found or produced
Transcription Factors are
proteins that regulate gene expression, genes have to be turned on at the right time and place for development
Secreted signaling molecules are involved in
cell-to-cell communication by signalling transduction cascades
Cell surface receptor proteins are
responsible for receiving signals and propagating them intracellularly.
What is essential for development to proceed?
Differential gene expression and cell communication
All animals share what
the same classes of transcription factors and signalling molecules.
8 histone proteins and 4 types of histone proteins which are
H2B, H3, H4, H2A AND THEY HAVE TAILS!!
Condensed nucleosomes have histone tails that are
mostly methylated
Uncondensed nucleosomes have histone tails that are largely
unmethylated and acetylated
So how does methylation work?
methyls have a lysine which is positive and since the backbone of DNA in negative they get super close!!
What do enhancers and promoters really do?
promoted initiate, enhancers regulate speed/rate
Transcription factors, and functions for Hox
hoxa1, hoxb2…; Axis formation
POU
Pit1, Unc-86, Oct2; Pituitary, neural fate
Lim
lim1, forkhead; head development
Pax1
Pax1 ect; neural specification, eye + muscle developmetn
Basic helix-loop-helix
MyoD, MITF, Daughterless; muscle + nerve specification, pigmentation, sex in drosophila
Basic leucine zipper
Cebp, AP1, MITF; liver, fat cells
Standard zinc-finger
WT1, KRUPPEL, Engrailed; kidneys, gonad and macrophage development
Nuclear hormone receptors - zinc-finger
Glucocorticoid receptor, estrogen, testosterone, retinoice receptors; Secondary sex determ, limbs
Sry-sox
Sry, SOxD, Sox2; Bend DNA, mammalian primary sex determ, ectoderm
The three major domains of a transcription factor are
- DNA Binding domain
- trans-activating domain
- protein-protein interaction domain
(watch smth?)
What are the two ways u can modify a nucleosome through methylated DNA?
- add a methyl group and take away an acetyl therefore compacting DNA (deacetylase comes in)
- add more than one methyl
What binding protein is attracted to methylated regions
MECP2
The 2 DNA methyltransferases are
Dnmt3 (de novo methyltransferase) -recognizes unmethylated cytosines
Dnmt1 (perpetuating methyl transferase)- recognized methylated c’s and methylates the c on the opposing strand
Where does DNA get methylated?
on cytosine (CpG islands play a role on this too)
cassest exon
cutting out the middle keeping the ends
Mutually exclusive exons
1 gene cut two ways will give 2 products?
Alt 5’ splice site exons
retains the 5’ region
Alt 3’ splice site exons
retains the 3’ region
Homotypic exclusion/self-avoidance is when
a neuron avoids making a protein or smth that the same as other ones cuz it can sense its neighbour?
What are cadherins?
transmembrane proteins that are critical for the segregation of cell types in embryo (cadherin are the molecule in morphogenesis)
How do epithelial cells sort?
by the type of cadherin proteins present in their cell membranes
for example, epithelial cells transition to mesenchymal cells when
e-cadeherin expression is repressed (cuz e-cadherin is needed for cells to stick)