Question 1

A researcher knocks out expression of the POU domain transcription factor Oct4 in the early epiblast of a mouse embryo.Which cell type would you expect to be affected?

Accepted Answer

Oct4 is important for the formation of primordial germ cells in early embryonic development, so knocking out its expression is likely to affect the development of these cells.

Question 2

A newborn girl is suspected of having Turner syndrome.Which diagnostic procedure would be used to determine if this is indeed the case?

Accepted Answer

Karyotyping is the gold standard diagnostic procedure for Turner Syndrome, as it visualizes the entire complement of chromosomes and can identify the characteristic missing X chromosome in affected individuals. SKY, CGH, and FISH are all molecular cytogenetic techniques that can complement or confirm the results of karyotyping, but are not typically used as the initial diagnostic tool for Turner Syndrome.

Question 3

The birth control pill acts by blocking which process?

Accepted Answer

The birth control pill acts by preventing ovulation, which means that no mature egg is released from the ovaries to be fertilized by sperm.

Question 4

A child with a large sacrococcygeal teratoma is delivered by cesarean section.The teratoma likely arose from which type of cells?

Accepted Answer

Sacrococcygeal teratomas typically arise from pluripotent primordial germ cells, which can differentiate into various tissue types.

Question 5

A 36-year-old woman is unable to conceive a child because both her oviducts were severely scarred by pelvic inflammatory disease resulting from gonorrhea.Which type of assisted reproductive technology could be used to help her conceive?

Accepted Answer

Since the woman's oviducts are severely scarred, neither GIFT nor ZIFT would be a viable option as both require at least one functional oviduct. Therefore, the best option would be IVF and embryo transfer, where fertilization occurs outside the body in a laboratory and the resulting embryos are transferred into the woman's uterus.

Question 6

Increase in the levels of which hormone prevents menstruation during a cycle in which fertilization occurs?

Accepted Answer

hCG (human chorionic gonadotropin) is a hormone produced by the cells that form the placenta after a fertilized egg implants in the uterus. It maintains the corpus luteum, which produces progesterone to sustain the early pregnancy and prevent the shedding of the endometrium (menstruation). Therefore, an increase in hCG levels prevents menstruation during a cycle in which fertilization occurs.

Question 7

RU-486 is an effective abortifacient.It acts by which mechanism?

Accepted Answer

RU-486, also known as mifepristone, acts as an effective abortifacient by blocking the action of progesterone, leading to changes in the uterine lining and causing menstruation, which results in the termination of pregnancy.

Question 8

A baby is diagnosed with Down syndrome shortly after birth.Which of the following events occurred abnormally during prenatal development?

Accepted Answer

Down syndrome is caused by the presence of an extra copy of chromosome 21. This occurs during meiosis when nondisjunction occurs, meaning the chromosomes fail to separate properly during anaphase. The resulting gamete (sperm or egg) that receives two copies of chromosome 21 will contribute to the fetus having Down syndrome. Therefore the abnormal event during prenatal development that leads to Down syndrome is anaphase of meiosis.

Question 9

Formation of haploid spermatozoa occurs during which developmental event?

Accepted Answer

Spermatogenesis is the process by which haploid spermatozoa are produced from germ cells in the testes. This involves several stages, including the division of diploid spermatogonial stem cells into haploid spermatozoa through meiosis.

Question 10

A researcher establishes mouse spermatozoa lacking one of the following two sperm-specific proteins: Izumo and CD9.Which developmental events will be perturbed in the absence of either of these proteins?

Accepted Answer

Izumo and CD9 are crucial for the fusion of the egg and spermatozoa membranes. Izumo is a sperm protein essential for sperm-egg fusion, while CD9 is an egg protein that facilitates this process.

Quiz 2: Gametogenesis, Fertilization, and First Week