Trigger for Limb Development - Correct Answer Decreasing food, decreasing reproductive opportunities, more competition
From which group of fish did tetrapods arise from? - Correct Answer Ray-finned fishes (actinopterygii) and lobe-finned fishes (sarcopterygii)
Which ancient fish limbs is ...
ZOO3603C Exam 3 Questions &
Complete Solutions
Trigger for Limb Development - Correct Answer Decreasing food, decreasing
reproductive opportunities, more competition
From which group of fish did tetrapods arise from? - Correct Answer Ray-finned fishes
(actinopterygii) and lobe-finned fishes (sarcopterygii)
Which ancient fish limbs is more likely to have evolved into tetrapod limbs? - Correct
Answer Coelacanth fin strucutre (homologous elements)
What digit limb evolved first? - Correct Answer Five digit limbs (not a basal trait of all
tetrapods)
Pentadactyl limbs - Correct Answer Better weight bearing (fin with a wrist)
Where do digits come from? - Correct Answer Lepidotrichia lost at the same time as
new autopods evolved (lose and gain digits at the same time)
Tetrapod limb is made up of two independent parts
Hox genes involved in autopod appearance - Correct Answer as you knock out genes
of the Hoxd13 group you decrease the length and lose digits
How did limbs evolve? - Correct Answer Second domain of Hoxd expression
Zebrafish limb development - Correct Answer No second domain and the genome
duplicates again to create 8 Hox genes
What does Hox13 knockout do in zebrafish? - Correct Answer Deletes lepidotrichia
What does double and triple knockout of Hoxa and Hoxd do? - Correct Answer
reduces or deletes autopod and fin rays
What do alternating enhancers do? - Correct Answer Change limbs (not genes)
Are lepidotrichia homologous to digits? - Correct Answer True
Python gene expression and what is it caused by? - Correct Answer Low Shh
expression = reduced hindlimbs
Caused by a change in the enchancer known as ZRS
What happens with you replace mouse ZRS with those of a python? - Correct Answer
No limbs (17 bp deletion)
, How do you lose structures in limbs? - Correct Answer Small alterations to an
enhancer NOT by huge gene deletions
How did digit modifications evolve? - Correct Answer independently many times
throughout vertebrates
Evolution of digit loss in cows - Correct Answer Lost one digit fully and digits 2/5 are
reduced to vestigial splints
Shh pathway in digit loss of cows - Correct Answer Shh diffuses further anterior in the
cow limb
How Shh works in cow limb? - Correct Answer Shh is a ligand protein and binds to a
membrane receptor known as Ptch1, and once this is activated Gli1 moves to nucleus
to facilitate transcription (downstream)
Enhancer evolution in cow digit loss - Correct Answer Limb regulatory module (LRM)
regulates Ptch1 expression in mouse limbs and cows version drives expression in
smaller region
What does the loss of Ptch1 in the mouse do? - Correct Answer Recreates the cow
digit phenotype
Bat digit elongation - Correct Answer Fgf8
Webbing of bat limbs - Correct Answer Grem1
Enhancer evolution in cow digit loss - Correct Answer
Genes involved in CNS DV patterning - Correct Answer Wnt/FGF/RA
Morphogens in CNS - Correct Answer floor plate and notochord
What generates interneurons? - Correct Answer RA required for shh-independent
pathway
Where is RA? - Correct Answer adjacent somite
What does RA do to Shh? - Correct Answer Stops from expressing too much
Dorsal patterning - Correct Answer no notochord=roofplate expands
What induces dorsalin? - Correct Answer BMPs from ectoderm and then roofplate
itself
What do BMPs do? - Correct Answer dorsal patterning
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