Exam 1

Question 1

What is the most common condition associated with spontaneously aborted embryos?

a. maternal imprinting
b. paternal imprinting
c. ectopic pregnancy
d. chromosomal abnormalities
e. lack of X-chromosomal inactivation

Answer 1

d. chromosomal abnormalities

Question 2

What tissue from the implanting embryo directly interfaces with the endometrial connective tissue?

a. corona radiata
b. inner cell mass
c. extraembryonic membrane
d. epiblast
e. syncytiotrophoblast

Answer 2

e. syncytiotrophoblast

Question 3

Identical twinning is made possible by what process or property of the early embryo?

a. regulation
b. aneuploidy
c. paternal imprinting
d. maternal imprinting
e. X-chromosomal inactivation

Answer 3

a. regulation

Question 4

The zona pellucida:

a. aids in penetration of the endometrial epithelium
b. serves as a source of nutrients for the embryo
c. prevents premature implantation of the cleaving embryo
d. all of the above
e. none of the above

Answer 4

c. prevents premature implantation of the cleaving embryo

Question 5

Of the barriers to sperm survival and transport within the female reproductive tract, low pH is most important in the:

a. upper uterine tube
b. lower uterine tube
c. uterine cavity
d. cervix
e. vagina

Answer 5

e. vagina

Question 6

The principal energy source for ejaculated spermatozoa is:

a. prostatic acid phosphatase
b. internal glucose
c. prostatic citric acid
d. fructose in seminal vesicle fluid
e. glycogen released from the vaginal epithelium

Answer 6

d. fructose in seminal vesicle fluid

Question 7

During spermatogenesis, histone is replaced by which of the following, to allow better packing of the condensed chromatin in the head of the spermatozoon?

a. inhibin
b. prostaglandin E
c. testosterone
d. protamine
e. androgen-binding protein

Answer 7

d. protamine

Question 8

Which cell type is located outside the blood-testis barrier?

a. spermatozoon
b. secondary spermatocyte
c. spermatid
d. primary spermatocyte
e. spermatogonium

Answer 8

e. spermatogonium

Question 9

Which of the following cells normally participates in mitotic divisions?

a. primary oocyte
b. oogonium
c. primary spermatocyte
d. spermatid
e. secondary spermatocyte

Answer 9

b. oogonium

Question 10

In a routine chest x-ray examination, the radiologist sees what appear to be teeth in a mediastinal mass. What is the likely diagnosis, and what is a probable embryological explanation for its appearance?

Answer 10

A mediastinal teratoma, which is likely to have arisen from an aberrant primordial germ cell that became lodged in the CT near the heart.

Question 11

When does meiosis begin in the female and in the male?

Answer 11

Females: meiosis begins during embryonic life
Males: meiosis begins at puberty

Question 12

At what stages of oogenesis is meiosis arrested in the female?

Answer 12

At prophase (diplotene stage) of meiosis I and at metaphase of the meiosis II

Question 13

What is the difference between spermatogenesis and spermiogenesis?

Answer 13

Spermatogenesis: entire process of sperm formation from a spermatogonium; includes the two meiotic divisions and the period of spermiogenesis.
Spermiogenesis, or sperm metamorphosis, is the process of transformation of a post meiotic spermatid, which looks like an ordinary cell, to a highly specialized spermatozoon.

Question 14

The actions of what hormones are responsible for the changes in the endometrium during the menstrual cycle?

Answer 14

Estrogen, secreted by the ovary, support the preovulatory proliferative phase. From the time of ovulation, progesterone is secreted in large amounts by the corpus luteum and is responsible for the secretory phase, which prepares the endometrium for implantation of an embryo.

Question 15

Sertoli cells in the testis are stimulated by what two major reproductive hormones?

Answer 15

Follicle-stimulating hormone (FSH) produced by the anterior lobe of the pituitary gland and testosterone produced by the Leydig cells of the testis.

Question 16

What is the principal hormonal stimulus for ovulation?

Answer 16

The sharp surge of luteinizing hormone (LH) produced by the anterior lobe of the pituitary gland

Question 17

What is capacitation?

Answer 17

Capacitation is a poorly understood interaction between a spermatozoon and female reproductive tissues that increases the ability of the sperm to fertilize an egg. In some mammals, capacitation is obligatory, but in humans the importance of capacitation is less well established.

Question 18

Where does fertilization occur?

Answer 18

Fertilization usually occurs in the upper third of the uterine tube (ampulla)

Question 19

Name two functions of the ZP3 protein of the Zona Pellucida.

Answer 19

The ZP3 protein acts as a specific sperm receptor through its O-linked oligosaccharides; much of its polypeptide backbone must be exposed to stimulate the acrosomal reaction.

Question 20

What is polyspermy, and how is it prevented after a spermatozoon enters the egg?

Answer 20

Polyspermy is the fertilization of an egg by more than one spermatozoon. It is prevented through the fast electrical block on the plasma membrane of the egg and by the later zone reaction, by which products released from the cortical granules act to inactivate the sperm receptors in the zona pellucida.

Question 21

A woman gives birth to septuplets. What is the likely reason for multiple births?

Answer 21

She had probably taken clomiphene for the stimulation of ovulation. Natural septuplets are almost never seen.

Question 22

When multiple oocytes obtained by laparoscopy are fertilized in vitro, why are up to three embryos implanted into the woman’s uterus, and why are the other embryos commonly frozen?

Answer 22

The introduction of more than one embryo into the tube of the woman is commonly done because the chance that any single implanted embryo will survive to the time of birth is quite small. The reasons for this are poorly understood. Extra embryos are frozen because if a pregnancy does not result from the first implantation, the frozen embryos can be implanted without the inconvenience and expense of obtaining new eggs from the mother and fertilizing them in vitro.

Question 23

Why do some reproductive technology centers insert spermatozoa under the zone pellucid or even directly into the oocyte?

Answer 23

In cases of incompatibility between the sperm and egg, poor sperm motility, or deficient sperm receptors in the zone, introducing the sperm directly into or near the egg can bypass a weak point in the reproductive sequence of events.

Question 24

What is the importance of the inner cell mass of the cleaving embryo?

Answer 24

The embryonic body proper arises from the inner cell mass

Question 25

Parental imprinting is a phenomenon showing that certain homologous maternal and paternal chromosomes have different influences on the development of the embryo. Excess paternal influences result in the abnormal development of what type of tissue at the expense of development of the embryo itself?

Answer 25

Trophoblastic tissues

Question 26

What is the function of integrins in implantation?

Answer 26

Interns allow the trophoblast of the embryo to adhere to the uterine epithelium

Question 27

What is the cellular origin of the syncytiotrophoblast of the implanting embryo?

Answer 27

Cells derived form the cytotrophoblast fuse to form the syncytiotrophoblast (book says this but Anderson says from the trophoblast)

Question 28

A woman who is 2 to 3 months pregnant suddenly develops severe lower abdominal pain. In the differential diagnosis, the physician must include the possibility of what condition?

Answer 28

In addition to the standard causes of lower abdominal pain, such as appendicitis, the physician should consider ectopic pregnancy (tubal variety) as a result of stretching and possible rupture of the uterine tube containing the implanted embryo.

Question 29

What is a homeobox?

Answer 29

A homeobox is a highly conserved region consisting of 180 nucleotides that is found in many morphogenetically active genes. Homeobox gene products act as transcription factors.

Question 30

Which of the following is a transcription factor?

a. FGF
b. Pax
c. TGF
d. Notch
e. Wnt

Answer 30

b. Pax

Question 31

Where in the cell is the retinoic acid receptor located?

Answer 31

In contrast to many receptors, the receptors for retinoic acid (α, β, and γ) are located in the nucleus.

Question 32

A mutation of what receptor is the basis for basal carcinomas of the skin?

a. Patched
b. Retinoic acid
c. Notch
d. FGF receptor
e. None of the above

Answer 32

a. Patched

Question 33

Zinc fingers or helix-loop-helix arrangements are characteristic of members of what class of molecules?

a. Proto-oncogenes
b. Signaling molecules
c. Receptors
d. Transcription factors
e. None of the above

Answer 33

d. Transcription factors

Question 34

Based on your knowledge of paralogous groups, which gene would be expressed most anteriorly in the embryo?

a. Hoxa-13
b. Hoxc-9
c. Hoxd-13
d. Hoxb-1
e. Hoxb-6

Answer 34

d. Hoxb-1

Question 35

Sonic hedgehog is produced in which signaling center?

a. Notochord
b. Intestinal portals
c. Floor plate of neural tube
d. Zone of polarizing activity in the limb bud
e. All of the above

Answer 35

e. All of the above

Question 36

The principal inductor in primary neural induction is the:

a. Hypoblast
b. Primitive streak
c. Extraembryonic mesoderm
d. Notochordal process
e. Embryonic ectoderm

Answer 36

d. Notochordal process

Question 37

Which of the following tissues arises from cells passing through the primitive streak?

a. Embryonic endoderm
b. Hypoblast
c. Cytotrophoblast
d. Primary yolk sac
e. Amnion

Answer 37

a. Embryonic endoderm

Question 38

Cells of which germ layer are not present in the oropharyngeal membrane?

a. Ectoderm
b. Mesoderm
c. Endoderm
d. All are present

Answer 38

b. Mesoderm

Question 39

The prechordal plate plays an important role in regionalization of the:

a. Notochord
b. Forebrain
c. Embryonic mesoderm
d. Primitive node
e. Hindbrain

Answer 39

b. Forebrain

Question 40

Brachyury, a deficiency in caudal tissues in the body, is caused by a mutation in what gene?

a. Lim-1
b. Noggin
c. T
d. Sonic hedgehog
e. Activin

Answer 40

c. T

Question 41

Which layer of the bilaminar (two-layered) embryo gives rise to all of the embryonic tissue proper?

Answer 41

The epiblast.

Question 42

Of what importance is the primitive node in embryonic development?

Answer 42

The primitive node acts as the organizer of the embryo. Through it pass the cells that become the notochord. The notochord induces the formation of the nervous system. The primitive node is also the site of synthesis of morphogenetically active molecules, such as retinoic acid. If a primitive node is transplanted to another embryo, it stimulates the formation of another embryonic axis.

Question 43

The migration of mesodermal cells from the primitive streak is facilitated by the presence of what molecules of the extracellular matrix?

Answer 43

Hyaluronic acid and fibronectin.

Question 44

What molecules can bring about mesodermal induction in an early embryo?

Answer 44

Vg1 and activin.

Question 45

At what stage in the life history of many cells are cell adhesion molecules lost?

Answer 45

Cell adhesion molecules are lost in a migratory phase. When the migratory cells settle down, they may re-express cell adhesion molecules.