BIO 351
BIO 351 - Exam 3 Fall 2025 Questions With
Correct Detailed Answers
1. A 25 year old man visit his doctor to determine the cause of his infertility. Semen analysis results in a
diagnosis of azoospermia. You suspect that there may be a _____.
a. blockage of the vas deferens.
b. spermiogenesis defect.
c. loss of dihydrosterone.
d. abuse of estrogen. - ANSWER ✔ - a. blockage of the vas deferens.
or...
b. spermiogenesis defect.
2. In studying a genetic form of Hirschsprung's disease due to an EDN3 mutation, you have identified a
selective defect in the migration of sacral neural crest. Based on your understanding of enteric neural
crest migration, which of the following regions of the GI tract would you expect to be most affected?
a. colon.
b. liver.
c. pancreas.
d. stomach.
e. esophagus. - ANSWER ✔ - a. colon.
3. During early development, the gut tube becomes separated from which structure?
a. notochord.
b. yolk sac.
c. neural tube.
d. heart.
e. somites. - ANSWER ✔ - b. yolk sac.
4. Myelin is formed by ____ in the peripheral nervous system and ____ in the central nervous system.
a. astrocytes, ependymal cells.
b. ependymal cells, astrocytes.
c. oligodendrocytes, schwann cells.
d. parasympathetic neurons, sympathetic neurons.
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, BIO 351
e. schwann cells, oligodendrocytes. - ANSWER ✔ - e. schwann cells, oligodendrocytes.
5. You laboratory has identified a rare loss-of-function mutation in runx1. runx1 is a transcription factor
that normally promotes the differentiation of trka epxressing neurons in the DRG. Which of the
following phenotypes would you predict in a runx1- mouse model?
a. hypersensitivity to pain.
b. enhanced muscle stretch reflexes.
c. reduced sensitivity to pain.
d. decreased muscle stretch reflexes. - ANSWER ✔ - c. reduced sensitivity to pain.
6. What strucures derive from the otic placode?
a. cochlea and semicircular canals.
b. lens.
c. malleus and ear drum.
d. stapes, incus, and malleus.
e. vestibulocochlear nerve. - ANSWER ✔ - a. cochlea and semicircular canals.
7. Hydrocephalus often results from a disruption in cerebrospinal fluid (CSF) flow leading to abnormal
swelling of the cerebral ventricles (see MRI images). What cell type plays an important role in
promoting CSF flow via movement of cilia on the apical cell surface?
a. endothelial cells.
b. oligodendrocytes.
c. astrocytes.
d. ependymal cells. - ANSWER ✔ - d. ependymal cells.
8. The diagrams below shut two lower motor neurons innervating two muscle fibers at different stages
of development. Which diagram provides the best example of a fully mature, adult pattern of
connectivity? - ANSWER ✔ - B.
9. While hiking, your arm gets caught by the thorns of an ocotillo plant, tearing the skin. Eventually, the
skin heals by producing thickened scar tissue. This is an example of...
a. stem cell mediated regeneration.
b. morphallactic regeneration.
c. epimorphic regeneration.
d. tissue repair.
2|P a g e
BIO 351 - Exam 3 Fall 2025 Questions With
Correct Detailed Answers
1. A 25 year old man visit his doctor to determine the cause of his infertility. Semen analysis results in a
diagnosis of azoospermia. You suspect that there may be a _____.
a. blockage of the vas deferens.
b. spermiogenesis defect.
c. loss of dihydrosterone.
d. abuse of estrogen. - ANSWER ✔ - a. blockage of the vas deferens.
or...
b. spermiogenesis defect.
2. In studying a genetic form of Hirschsprung's disease due to an EDN3 mutation, you have identified a
selective defect in the migration of sacral neural crest. Based on your understanding of enteric neural
crest migration, which of the following regions of the GI tract would you expect to be most affected?
a. colon.
b. liver.
c. pancreas.
d. stomach.
e. esophagus. - ANSWER ✔ - a. colon.
3. During early development, the gut tube becomes separated from which structure?
a. notochord.
b. yolk sac.
c. neural tube.
d. heart.
e. somites. - ANSWER ✔ - b. yolk sac.
4. Myelin is formed by ____ in the peripheral nervous system and ____ in the central nervous system.
a. astrocytes, ependymal cells.
b. ependymal cells, astrocytes.
c. oligodendrocytes, schwann cells.
d. parasympathetic neurons, sympathetic neurons.
1|P a g e
, BIO 351
e. schwann cells, oligodendrocytes. - ANSWER ✔ - e. schwann cells, oligodendrocytes.
5. You laboratory has identified a rare loss-of-function mutation in runx1. runx1 is a transcription factor
that normally promotes the differentiation of trka epxressing neurons in the DRG. Which of the
following phenotypes would you predict in a runx1- mouse model?
a. hypersensitivity to pain.
b. enhanced muscle stretch reflexes.
c. reduced sensitivity to pain.
d. decreased muscle stretch reflexes. - ANSWER ✔ - c. reduced sensitivity to pain.
6. What strucures derive from the otic placode?
a. cochlea and semicircular canals.
b. lens.
c. malleus and ear drum.
d. stapes, incus, and malleus.
e. vestibulocochlear nerve. - ANSWER ✔ - a. cochlea and semicircular canals.
7. Hydrocephalus often results from a disruption in cerebrospinal fluid (CSF) flow leading to abnormal
swelling of the cerebral ventricles (see MRI images). What cell type plays an important role in
promoting CSF flow via movement of cilia on the apical cell surface?
a. endothelial cells.
b. oligodendrocytes.
c. astrocytes.
d. ependymal cells. - ANSWER ✔ - d. ependymal cells.
8. The diagrams below shut two lower motor neurons innervating two muscle fibers at different stages
of development. Which diagram provides the best example of a fully mature, adult pattern of
connectivity? - ANSWER ✔ - B.
9. While hiking, your arm gets caught by the thorns of an ocotillo plant, tearing the skin. Eventually, the
skin heals by producing thickened scar tissue. This is an example of...
a. stem cell mediated regeneration.
b. morphallactic regeneration.
c. epimorphic regeneration.
d. tissue repair.
2|P a g e
