Chapter 8 & 9 Flashcards
what makes goosecoid?
spemann organizer
what activates the release of goosecoid? what does goosecoid do?
nodal expression from the Nieuwkoop Center
- blocks BMPs so NS is formed (not skin)
what are the two types of proteins released by the organizer? give examples of each
nuclear (goosecoid, twin, siamois)
secreted (chordin, frzb, noggin, Shh, nodal, dickkopf, cerberus)
- secreted proteins are released by nuclear proteins
where in the cell are E-cadherins found?
epidermis (skin)
what does Chordin do?
binds directly to BMPs to inactivate it
- turned on by migrated IMZ cells
- rescues ectodermal cells from skin fate
what is the default pathway of ectodermal cells?
neural tissue
what are BMPs?
bone morphogenic proteins
- induces the skin fate
- occurs when chordin is blocked (no NS)
who created einstucking?
Otto Mangold (1933)
talk about the einstucking experiment where he took 4 regions of the archenteron from a LATE gastrula and put them into an EARLY gastrula blastocoel
when he took different regions of the archenteron (already has NS and has migrated) and grafted them, each region formed an extra part of an embryo depending on which section of the the tissue he extracted it from
talk about the einstucking experiment where he took the dorsal blastopore lip of an EARLY gastrula and put it into another EARLY gastrula
vs
taking the lip from a LATER stage gastrula and putting it into another EARLY gastrula
the early gastrula lip formed a second head
the later stage gastrula lip formed a second tail
- proved that the first organizer cells make the head first, and then the later cells form a tail
what two molecules explain the einstucking experiment?
BMP
Wnt
what happens when both BMP and Wnt are activated?
form epidermis (skin)
what happens when only Wnt are active and BMPs are blocked?
- what is blocking BMP?
posterior NS (spinal cord)
- chordin is blocking BMP
what happens when both BMP and Wnt are blocked? what does this mean in relation to the einstucking experiment?
anterior NS (brain)
- means that BMP and Wnt are both being blocked initially, and then Wnt eventually becomes activated
which region has the highest expression of Wnt (anterior or posterior)?
posterior (tail)
where are Wnt antagonists found? give examples
found in the head & form a gradient
- Frzb (MAIN ONE)
- Dickkopf, Cerberus, IGF (insulin-like GFs)
what does retinoic acid do? where do they have the highest expression
activates Wnt, Fgfs, and Shh
- found in the tail region (posterior)
what three molecules help differentiate the left side axis?
Vg1, Nodal (Xnr1), Pitx2
- Vg1 & Nodal are mainly on left side
- Pitx2 is only on left side
- due to the use of microtubules
what is an amniote?
things that have an amniotic sac
- adaptation to lay eggs on land instead of in the water
what is the chorioaliantoic MB? (CAM)
similar to placenta, but in chicks
- gas exchange, waste removal, protect embryo
what main structure helps form axes in chicks?
Hensens Node -> dorsal blastopore lip
- migrates cells inside to become mesoderm and induction of NS
describe the shape of a chick embryo. How do the cells migrate in the dorsal lip?
shaped like a disc (stuffed crust pizza)
- cells from top migrate inward, and then out & up
what are the cells called on the top side of the embryo? bottom side of embryo?
top = epiblast
bottom = hypoblast
what is the pathway on the left side of a chick embryo that differentiates the axis?
- Shh activates Cerberus
- Cerberus blocks BMP to allow for activation of Nodal
- Nodal turns on Pitx2 (only on left side)
- must have threshold amount of Nodal for activation
what are the negatives to using mammals as model organisms?
- ethical concerns
- small eggs
- low production
- internal fertilization & development
- slow development (long generation times)
- asynchronous division (cells don’t divide at same rate)
- genome activation (MBT) occurs sooner
what are the positives to using mice as model organisms?
- easy to breed
- easily housed
- large litters
- short generation times
what happens on day 1 of fertilization?
first division
what day is the embryo a morula? (uneven cells)
day 4
what day does the embryo enter the uterus?
day 5
what day does the embryo implant into the endometrium?
day 7
what day is gastrulation?
day 14-16
what week is nerulation?
week 3
what weeks is organogenesis?
week 3-8
when is the embryo called a fetus?
week 8
what does allometry mean?
parts of the body grows at different rates
- big head on a baby
what type of cleavage do mammals do?
rotational cleavage
after what division are the embryo cells no longer totipotent (now pluripotent)? what type of cell is it?
after the 4th division
- cells are a blastula
what two structures are differentiated in the pluripotent cell?
trophoblastic cells (placenta)
inner cell mass (embryo, MBs, amniotic sac)
what signal is expressed in the ICM to block trophoblastic fate?
Oct4
- known as the pluripotent signal
describe the steps of implantation
- egg released proteolytic enzymes to chew up zona pellucida (gets rid of slippery layer) as it enters the uterus
- embryo embeds into mother (proteolytic enzymes, polysaccharides, ECM proteins, hyalin-related proteins)
- enzymes are used to prevent rejection of the egg - ICM divides into two layers (epiblast, hypoblast)
- mother’s blood vessels (trophoblastic lacunae) form around embryo
- does not directly connect, molecules diffuse over
what does the epiblast and hypoblast become?
epiblast = mesoderm, ectoderm, endoderm
hypoblast = becomes nutrients & yolk sac
what is the chorion?
the area that the molecules diffuse over to the embryo form the mother
- made by trophoblastic cells
- baby picks up O2 form mom thru umbilical cord ( 2 arteries, 1 vein)
what is the allantois?
gets rid of waste by giving it to mom
what are monozygotic twins?
identical twins
- one sperm, one egg
what are the three ways monozygotic twins form?
- blastomeres separate before blastula forms (day 0-5)
- two cells (1st divison) pull apart form each other
- 2 chorions (2 implantations), 2 amniotic cavities - ICM separates before amniotic cavity forms (days 5-9)
- implantation has occurs
- 1 chorion (1 implantation), 2 amnions - Node separates before gastrulation (after day 9)
- 1 chorion, 1 amnion
what are dizygotic twins?
fraternal twins
- two sperm, two eggs
what are chimera twins (un-twins)? how do they form?
two mouse embryos at early cleavage stage (morula) stick to each other before they are implanted
- creates only 1 embryo that is a mixture of both (calico)
- regulative / conditional specification (induced by neighbors)
which hox genes are dominant, posterior or anterior?
posterior
what are paralogous genes?
same gene family, different location (A1, B1, C1, D1)
- on a different chromosome
describe the lose it experiment for hox genes
remove hox10 = lost lumbar region
- created more thoracic
- anteriorizes
remove hox11 = lost sacral region
- created more lumbar
- anteriorizes
describe the move it experiment for hox genes
add RA = makes cervical spine, thoracic
- posteriorizes
less RA = makes thoracic spine, cervical
- anteriorizes
describe the find it experiment for hox genes
chick vs mice (comparative anatomy)
- chick = 14 C, 7 T, 12 L/S, 5 COX
- mice = 7 C, 13 T, 6 L, 4S
- determined specific hox genes make specific vertebrae
- hox5/hox6 (C/T)
described what happened to limb growth when RA was added to a limb after wrist amputation
proximalizes the limb
- hox genes tell it is more proximal than it actually is
- created an entire new arm starting at the wrist, when all it needed was a new hand
how is vitamin A related to RA?
vitamin A is converted to RA
- can cause issues when taking a megadose
naming of Hox genes in relation to humans, mice, and flies
HOX = humans
Hox = mice
Hom-C = flies
