Deck 19: Development of the Limbs

Question 1

Dispatched 1 is essential for diffusion of Shh.In the Dispatched mouse mutant,which digit does not develop?

A) Digit 1, the most anterior (cranial) digit
B) Digit 2
C) Digit 3
D) Digit 4
E) Digit 5, the most posterior (caudal) digit

Answer 1

B

Question 2

When Lmx1b is genetically inactivated in mice,how do the LMCl and LMCm motor neurons migrate?

A) All into the ventral mesenchyme
B) Randomly throughout the limb bud
C) All into the dorsal mesenchyme

Answer 2

B

Question 3

Shh signaling is essential for normal patterning of the digits.Fate labeling studies have shown that the digits are patterned by a combination of the dose,diffusion,and length of exposure to Shh signaling.Which digit is dependent solely on diffusion of Shh for its development?

A) Digit 1, the most anterior (cranial) digit
B) Digit 2
C) Digit 3
D) Digit 4
E) Digit 5, the most posterior (caudal) digit

Answer 3

B

Question 4

Which region of the developing limb specifies the cranial-caudal axis of the developing limb bud?

A) AER
B) ZPA
C) Dorsal ectoderm

Question 5

Mutations in the transcription factor p63 (also known as TP73L) in humans can affect the development of the limbs.What is the phenotype of the limbs when this gene is mutated?

A) Amelia
B) Meromelia
C) Syndactyly
D) Polydactyly
E) Split hand/foot

Question 6

What term describes the typical limb phenotype of children who have been exposed to thalidomide during prenatal development?

A) Amelia, ectromelia
B) Adactyly
C) Meromelia
D) Oligodactyly
E) Phocomelia

Question 7

Aristaless-like 4 (Alx4) is a homeobox gene involved in the establishment of the limb pattern. What is the phenotype of the Alx4 mouse mutant (Strong's Luxoid)?

A) Amelia
B) Meromelia
C) Syndactyly
D) Polydactyly
E) Split hand/foot

Question 8

The term arachnodactyly specifically refers to which defect?

A) Absence of the entire limb
B) Absence of part of the stylopod
C) Presence of extra digits
D) Fusion of digits
E) Absence of one or more digits
F) Elongation of the digits

Question 9

Researchers have shown that the HoxA and D complex of transcription factors,which are expressed in nested domains within the limb bud,are essential for outgrowth and normal patterning of the limb bud.This is clearly shown by the genetic inactivation of Hoxa11 and Hoxd11.In the forelimb,which structure(s) is/are affected?

A) Humerus
B) Radius and ulna
C) Carpals
D) Metacarpals
E) Phalanges

Question 10

Shh signaling is essential for normal patterning of the digits.When Shh signaling is genetically inactivated in mice,which digit forms?

A) Digit 1, the most anterior (cranial) digit
B) Digit 2
C) Digit 3
D) Digit 4
E) Digit 5, the most posterior (caudal) digit

Question 11

The AER,the thickened ectoderm at the distal tip of the limb bud,controls limb outgrowth.Genetic inactivation experiments in mice and manipulation studies in chicks have identified the key factors expressed in the AER that control outgrowth once the limb bud has formed.What family of growth factors in the AER promotes outgrowth?

A) Bmp
B) Fgfs
C) Wnts
D) Shh

Question 12

Which signaling factor is essential for patterning of the limb across the cranial-caudal axis?

A) Shh
B) Wnt7a
C) Wnt5a
D) Fgf8
E) Bmp2

Question 13

Which gene is mutated in hand-foot-genital syndrome?

A) HOXA11
B) HOXA13
C) HOXD13
D) TBX3
E) TBX5

Question 14

Gli3 is essential for normal limb development.In mice,mutation of Gli3 results in which limb defect?

A) Amelia
B) Meromelia
C) Syndactyly
D) Polydactyly
E) Split hand/foot

Question 15

Which growth factor is expressed by the dorsal limb ectoderm and is essential for patterning the dorsal-ventral axis?

A) Wnt3a
B) Wnt7a
C) Shh
D) Wnt5a
E) Fgf8

Question 16

Nail-patella syndrome is caused by mutations in which gene?

A) WNT7a
B) ENGRAILED-1
C) FGF8
D) NOGGIN
E) LMX1B