Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
65 Cards in this Set
- Front
- Back
|
What type of cleavage do mammals undergo?
|
Isolecithal (holoblastic); ROTATIONAL cleavage
|
|
|
T/F Cleavage in mammals is synchronous
|
F; Sometimes odd # of cells
|
|
|
Zygotic genes are activated after which cell division?
|
b/w 4 and 8 cell stages
|
|
|
MBToccurs at what cell stage?
|
2
|
|
|
After the 3rd cleavage, cell adhesion molecules are expressed such as E-cadherin and what happens?
|
compaction
|
|
|
What are trophoblast cells?
|
Outer region of morula that pruduces NO embryonic structures. It forms tissue of chorion (portion of placenta)
|
|
|
What does chorion do?
|
Allows fetus to get oxygen and nourishment from the mother and secretes hormones so Mom doesnt reject it.
|
|
|
What is the purpose of compaction?
|
So it can form a blastocoel! (Cells can tolerate high pressure)
|
|
|
The Inner cell mass (ICM) generates what?
|
embryo and associated yolk sac
|
|
|
ICM is (pluripotent/totipotent) and the earliest blastomere cells are (pluripotent/totipotent)
|
pluripotent; totipotent
|
|
|
The morula is at what cell stage? What is the embryo called when the ICM becomes located on one side of the ring of trophoblast cells?
|
16; blastocyst
|
|
|
The zona pelliculda prevents blastocyst from doing what?
|
Attaching to the oviduct walls on its way to the uterus
|
|
|
How does the trophoblast (and ICM) leave the zona pellucida?
|
The trophoblast secretes an enzyme that digests a small part of the zona and the expanding blastocyst slides through
|
|
|
T/F Mammals rely on stored yolk for nutrients
|
F; They get nutrients from the mother
|
|
|
Placenta is made up of what two tissues
|
Chorion (fetal) + Dicidua(Maternal)
|
|
|
Chorion induces ______ to form maternal protion of the __________.
|
Uterine cells; placenta
|
|
|
The dicidua becomes rich in the ____ ____ that will provide oxygen and nutrients to the embryo.
|
blood vessels
|
|
|
How does embryo get its nutrients and exygen?
|
Through blood vessels in the dicidua
|
|
|
In mammals, what makes the yolk sac?
|
hypoblast
|
|
|
How does the hypoblast form?
|
delamination
|
|
|
Where does gastrulation begin in mammals?
|
Posterior of embryo where the node forms
|
|
|
Cells that migrate through the node give rise to what?
|
notochord
|
|
|
What coordinates cell migration and specification?
|
FGF (primitive streak makes and responds to it)
|
|
|
In absense of FGF8 gene, what happens?
|
Cells fail to migrate through primitive streak and mesoderm and endoderm do not form
|
|
|
How does FGF8 control cell mvmnt into primitive streak?
|
By downregulating E-cadherin that holds epiblast cells together
|
|
|
What other genes (besides FGF) are required for cell specification of mesoderm tissue?
|
Brachyury, snail, and Tbx6
|
|
|
Primitive streak is a site of ____ production.
|
Brachyury
|
|
|
What is a unique feature of the MOUSE epiblast?
|
It is an inverted cup (not disc shaped)
|
|
|
The dorsal side of the epiblast touches what tissue? What does the ventral side touch?
|
amniotic cavity; newly formed mesoderm
|
|
|
What are the two signaling centers in mammals?
|
Node and AVE (anterior visceral endoderm)
|
|
|
Do mammals have regulative development?
|
Rare.. b/c develops inside mother and there are no cytoplasmic determinants
|
|
|
What fates does AVE specify?
|
Head
|
|
|
MAMMALS
|
.
|
|
|
CHICK
|
.
|
|
|
What does the node (organizer) express?
|
Nodal, BMP antagonists
|
|
|
What happens in Nodal mutants?
|
No mesoderm, no head structure
|
|
|
What happens in Chordin mutants?
|
Not too much at early stages because redundancy of Noggin and Follistatin...embryo will die
|
|
|
What does AVE express?
|
Cerberus..and some organizer genes, but NOT Nodal, Noggin, or Chordin
|
|
|
Which organizer is formed 1st?
|
AVE..but it's the 2nd organizer!!
|
|
|
What is required to MAINTAIN AVE?
|
Nodal signaling
|
|
|
What does Cerberus do?
|
Blocks Wnt Nodal and BMP
|
|
|
Which is first to be induced: Node or AVE
|
Node
|
|
|
What are the two ways the node maintains AVE?
|
1. Node cells crawl up (like prechordal mesoderm)
2. Nodal signaling cascade factors |
|
|
Node is responsible for creating ____ and they work together to form ____.
|
all of the body; anterior region of the embryo
|
|
|
What eventually links the node and AVE (since initially they're on opposite sides of embryo)?
|
Notochord
|
|
|
What factors are NOT in head region?
|
Nodal, BMP, FGF, Wnt
|
|
|
What factors are in posterior?
|
Nodal, FGF, Wnt, RA
|
|
|
Is Chordin expressed in the node or the AVE?
|
Node
|
|
|
Does BMP specify posterior?
|
NO; Wnt, FGF, and RA do
|
|
|
What happens if you overexpress BMP?
|
No posterior
|
|
|
How does AP polarity become specified?
|
Expression of Hox genes
|
|
|
Primitive Streak produces ____ factors and the organizer and its derivatives produce ____.
|
Wnt, BMP, RA, FGF; BMP and Wnt antagonists
|
|
|
If something is a paralogue what is it? Ortholog?
|
all related but dif. function; closest related in a dif species
|
|
|
How many Hox clusters are there in mice?
|
4
|
|
|
What specifies AP identity?
|
Combinatorial code of Hox expression
|
|
|
Evidence of the combinatorial code of Hox expression?
|
1. Gene knockouts
2. Effects of RA 3. Comparative development |
|
|
What are gene knockouts?
|
Mice are constructed that lack both copies of one or more Hox genes
|
|
|
What was the example of gene targeting (knockouts)?
|
All 6 copies of Hox 10 were knocked out no lumbar vertebrae were formed (ribs instead). When all 6 copies of Hox 11 were knocked out, no Sacral vertebrae (lumbar instead)
|
|
|
What happens if there is excess RA in embryo?
|
Shifts in Hox gene expression occur such that the last cervical vertebra is turned into a thoracic vertebra (become more anterior)
|
|
|
What happens if there is not enough RA in embryo?
|
Hox gene expression becomes more posterior and the first thoracic vertebrae becomes a copy of the cervical vertebrae.
|
|
|
What factors regulate Hox gene expression?
|
Fgf, Wnt (both are POSTERIORIZING factors)
|
|
|
How many cervical vertebrae do all mammals have? Thoracic? Lumbar?Sacral? Caudal?
|
7; 13; 6; 4; 20+
|
|
|
Snakes lack limbs due to what?
|
Homeotic transformation: anterior Hox formation not there
|
|
|
Are role of Hox genes as AP specifiers been conserved?
|
yes
|
|
|
Have the mechanisms of Hox gene activation been conserved?
|
No; Gene cascade vs. cell signaling
|
