Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key


Play button


Play button




Click to flip

30 Cards in this Set

  • Front
  • Back
What is Accutane?
What is it used for?
What can it cause during development?
Oral retinoic acid
Used for the treatment of acne and acute promyelocytic leukemia
Can cause a wide range of birth defects by interfering with Hox gene expression
What can defective shh signaling cause?
Describe the mechanism of heart induction
The heart requires mesoderm (tissue of origin), endoderm, and the node.
The node secretes nodal (BMP)
Endoderm secretes a wnt inhibitor (Dickkopf-1)
Describe neural plate induction
The neural plate produces a neural plate inhibitor called BMP-4
Both noggin and chordin are produced by the node and mesoderm
Noggin and chordin are inhibitors or BMP-4, inhibiting the inhibitor of neural plate formation, leading to its formation
Where are Hox genes expressed first?
Posterior of the embryo
What causes the splitting of the brain into segments? (forebrain, midbrain, hindbrain)
The expression of Hox genes
From where is retinoic acid first expressed in the embryo?
The node
How many Hox genes are there and how many copies?
13 genes and four copies (A-D)
What do the Hox genes code for?
Transcription factors that regulate the expression of other genes
Where would HoxB 13 be expressed?
In the posterior of the embryo
Where would HoxD 2 be expressed?
Towards the anterior of the embryo
The limits of Hox gene expression forms what?
The margins of somites
If Hox 6 expression causes C4 to be made, what happens if Hox 5 is knocked out?
C4 is produced again
Knocking out a Hox gene causes the more anterior structure to be repeated
If Hox 6 normally causes C4 to be produced, what happens if Hox 5 is overexpressed?
C4 instead becomes C5; becomes more posterior
Do Hox genes expressed in the anterior have high or low sensitivity to retinoic acid?
High sensitivity
(only those with very high sensitivity can express at low concentrations of RA)
True or false:
More Hox genes are expressed in the posterior than the anterior
What is a possible reason for the four sets of Hox genes?
Because they are so important in development, having 3-4 copies of a gene provides redundancy and resistance to mutation; only require one copy to function
What induces the floorplate in the neural tube?
High concentrations of shh secreted by the notochord.
Low concentrations produce motor neurons in the basal plates
From what does the limb bud derive?
From what does the apical ectodermal ridge (AER) form? What is its orientation?
Arises from the surface ectoderm of the limb bud and is a thickening that runs along the anterior / posterior axis
Describe the zone of polarizing activity (ZPA) of the limb bud
The ZPA is located in the posterior of the limb bud
Describe induction of the limb bud
The Hox code causes the intermediate mesoderm to produce FGF-10, which induces the formation of limbs on the adjacent lateral plate mesoderm
Describe the action of the AER
Secretes FGF-4 and 8, which patterns the proximal-distal axis of the limb (humerus, radius, ulna)
What differentiates forelimb from hindlimb?
Hox patterning causes Tbx5 expression only in the forelimb, and Tbx4 only in the hindlimb
Describe the ZPA
Located in the posterior of the limb bud
High levels of shh leads to posterior structures like the ulna and pinkie, low levels leads to thumb and radius
How is the dorsal/ventral axis of the limbs determined?
Dorsal ectoderm secretes Wnt-7a Paws v. back of hands
What are the mediators of the different axes of the limbs?
Proximal / distal
Dorsal / ventral
Posterior / anteroir
Prox / distal = FGF-4 and 8 from AER
Dorsal / ventral = Wnt-7a from dorsal ectoderm
Posterior / anterior = shh from ZPA in posterior mesoderm
Explain how Hox genes pattern proximal / distal axis of limbs
Hox 9 through 13 is expressed in the distal region of the limb bud, and the anterior only expresses Hox 9
What leads to apoptosis of webbing between digits?
Expression of BMP-4
What causes webbing disorders?
Lack of BMP-4 expression or action