BIO 351
BIO 351 - Exam 2 Fall 2025 Questions With
Correct Detailed Answers
1. The image on the right is of a 24-hour old chick embryo. Cells in the epiblast migrate through the
structure delineated by the arrows to form the mesoderm and endoderm. What is the name of this
structure?
a. Somite’s.
b. zone of polarizing activity.
c. primitive streak.
d. anterior visceral endoderm.
e. apizal ectodermal ridge. - ANSWER ✔ - c. primitive streak
2. Which of the following abnormalities is a severe open neural tube defect caused by a failure of
rostral neural tube closure?
a. spina bifida.
b. waardenburg syndrome.
c. anacephaly.
d. transposition of the great arteries.
e. myelomeningocele. - ANSWER ✔ - c. anacephaly.
3. Which of the following is an important transcription factor for specifying early presomitic mesoderm
identity that acts, in part, via repression of neural tube fates?
a. sox2.
b. beta-catenin.
c. retinoic acid.
d. tbx6.
e. raldh2. - ANSWER ✔ - d. tbx6.
4. The somites are derived from which of the following early embryonic tissues?
a. trophoblast.
b. neural crest.
c. endoderm.
d. ectoderm.
1|P a g e
, BIO 351
e. mesoderm. - ANSWER ✔ - e. mesoderm.
5. In the diagram above, (B) points to the _____ which develops into the _______.
a. scelrotome, cartilage of the axial skeleton.
b. ventral-lateral lip of the dermamyotome, hypaxial muscles.
c. dorsal-medial lip of the dermamyotome, epaxial muscles.
d. dorsal-medial lip of the dermamyotome, hypaxial muscles.
e. ventral-lateral lip of the dermamyotome, epaxial muscles. - ANSWER ✔ - c. dorsal-
medial lip of the dermamyotome, epaxial muscles.
6. During heart development, which of the following represent the correct temporal order of events in
morphogenesis?
a. specification of the cardiogenic mesoderm, septation, looping, formation of the second
heart field.
b. formation of the second heart field, septation, specification of the cardiogenic
mesoderm.
c. specification of cardiogenic mesoderm, formation of heart primordia, formation of the
linear heart tube, looping and septation.
d. formation of the linear heart tube, specification of lateral plate mesoderm, formation of
second heart field, septation, and looping. - ANSWER ✔ - c. specification of cardiogenic
mesoderm, formation of heart primordia, formation of the linear heart tube, looping and
septation.
7. Cardiac neural crest migrates into the truncus arteriosus to separate the outflow tract into which of
the following two structures?
a. left ventricle, right ventricle.
b. ventricles, atria.
c. aorta, pulmonary artery.
d. esophagus, trachea.
e. inferior vena cava, superior vena cava. - ANSWER ✔ - c. aorta, pulmonary artery.
8. During the development of the gonads the cells of the genital ridge will invade the underlying
mesenchyme. What will the mesenchymal cells be induced to become?
a. primordial germ cell.
b. sertoli cells and leydig cells.
c. granulosa cells or sertoli cells.
2|P a g e
BIO 351 - Exam 2 Fall 2025 Questions With
Correct Detailed Answers
1. The image on the right is of a 24-hour old chick embryo. Cells in the epiblast migrate through the
structure delineated by the arrows to form the mesoderm and endoderm. What is the name of this
structure?
a. Somite’s.
b. zone of polarizing activity.
c. primitive streak.
d. anterior visceral endoderm.
e. apizal ectodermal ridge. - ANSWER ✔ - c. primitive streak
2. Which of the following abnormalities is a severe open neural tube defect caused by a failure of
rostral neural tube closure?
a. spina bifida.
b. waardenburg syndrome.
c. anacephaly.
d. transposition of the great arteries.
e. myelomeningocele. - ANSWER ✔ - c. anacephaly.
3. Which of the following is an important transcription factor for specifying early presomitic mesoderm
identity that acts, in part, via repression of neural tube fates?
a. sox2.
b. beta-catenin.
c. retinoic acid.
d. tbx6.
e. raldh2. - ANSWER ✔ - d. tbx6.
4. The somites are derived from which of the following early embryonic tissues?
a. trophoblast.
b. neural crest.
c. endoderm.
d. ectoderm.
1|P a g e
, BIO 351
e. mesoderm. - ANSWER ✔ - e. mesoderm.
5. In the diagram above, (B) points to the _____ which develops into the _______.
a. scelrotome, cartilage of the axial skeleton.
b. ventral-lateral lip of the dermamyotome, hypaxial muscles.
c. dorsal-medial lip of the dermamyotome, epaxial muscles.
d. dorsal-medial lip of the dermamyotome, hypaxial muscles.
e. ventral-lateral lip of the dermamyotome, epaxial muscles. - ANSWER ✔ - c. dorsal-
medial lip of the dermamyotome, epaxial muscles.
6. During heart development, which of the following represent the correct temporal order of events in
morphogenesis?
a. specification of the cardiogenic mesoderm, septation, looping, formation of the second
heart field.
b. formation of the second heart field, septation, specification of the cardiogenic
mesoderm.
c. specification of cardiogenic mesoderm, formation of heart primordia, formation of the
linear heart tube, looping and septation.
d. formation of the linear heart tube, specification of lateral plate mesoderm, formation of
second heart field, septation, and looping. - ANSWER ✔ - c. specification of cardiogenic
mesoderm, formation of heart primordia, formation of the linear heart tube, looping and
septation.
7. Cardiac neural crest migrates into the truncus arteriosus to separate the outflow tract into which of
the following two structures?
a. left ventricle, right ventricle.
b. ventricles, atria.
c. aorta, pulmonary artery.
d. esophagus, trachea.
e. inferior vena cava, superior vena cava. - ANSWER ✔ - c. aorta, pulmonary artery.
8. During the development of the gonads the cells of the genital ridge will invade the underlying
mesenchyme. What will the mesenchymal cells be induced to become?
a. primordial germ cell.
b. sertoli cells and leydig cells.
c. granulosa cells or sertoli cells.
2|P a g e
