Question 1

Which of the options given is not true of Drosophila germ-line development?&#10;A) Germ-line development begins in the anterior region of the egg&#10;B) Germ cells are derived from pole cells.&#10;C) Shifting the position of pole plasm shifts the position of germ cell specification&#10;D) Germ cells are specified by inheriting cytoplasmic determinants

Accepted Answer

Germ-line development in Drosophila begins in the posterior region of the egg, not the anterior.

Question 2

How many distinct germplasm regions are present in a zebrafish embryo?&#10;A) 1&#10;B) 2&#10;C) 3&#10;D) 4

Accepted Answer

D

Question 3

Which of the options given represents the pathway of primordial germ-cell migration in the mouse embryo?&#10;A) Hindgut - dorsal mesentery - primitive streak - genital ridge&#10;B) Primitive streak - hindgut - dorsal mesentery - genital ridge&#10;C) Dorsal mesentery - hindgut - primitive streak - genital ridge&#10;D) Primitive streak - dorsal mesentery - hindgut - genital ridge

Accepted Answer

Primordial germ cells in mice migrate from the primitive streak to the hindgut, then through the dorsal mesentery, and finally to the genital ridge.

Question 4

Which of the options given is true of mammalian oogenesis?&#10;A) Meiosis gives rise to four daughter cells of equal size&#10;B) Meiosis is complete only occurs after fertilization&#10;C) Meiosis gives rise to four genetically identical daughter cells&#10;D) Meiosis is completed while the female is an embryo

Accepted Answer

Meiosis in mammalian oogenesis is only completed after fertilization. Initially, the process is arrested at prophase I during the female's embryonic development and resumes only upon ovulation, with the second meiotic division completed upon fertilization by a sperm.

Question 5

Which type of embryo is formed from the activation of an unfertilized egg?&#10;A) Androgenetic&#10;B) Gynogenetic&#10;C) Parthenogenetic&#10;D) Epigenetic

Accepted Answer

Parthenogenetic embryos are formed from the activation of an unfertilized egg, a process that does not involve fertilization by a male sperm cell.

Question 6

Which of the following refers to the silencing of germ-cell-specific genes during early development?&#10;A) Germ-cell suppression&#10;B) Sex-specific inhibition&#10;C) Genomic imprinting&#10;D) Genetic printing

Accepted Answer

Genomic imprinting is a process by which certain genes are silenced depending on whether they are inherited from the mother or the father. This mechanism plays a crucial role in early development, including the silencing of germ-cell-specific genes.

Question 7

What is the name of the Golgi-derived vesicle located in the head of sperm that aids in its penetration of the egg?&#10;A) Cortical granule&#10;B) Zona pellucida&#10;C) Acrosome&#10;D) Cumulus

Accepted Answer

The acrosome is a Golgi-derived vesicle located in the head of the sperm that contains enzymes necessary for the sperm to penetrate the egg during fertilization.

Question 8

What is the name of the Golgi-derived vesicle located under the plasma membrane of an egg to block polyspermy?&#10;A) Cortical granule&#10;B) Zona pellucida&#10;C) Acrosome&#10;D) Cumulus

Accepted Answer

Cortical granules are secretory vesicles found in the egg's cortex (just beneath the plasma membrane) that release their contents into the space between the plasma membrane and the zona pellucida in response to fertilization. This release modifies the zona pellucida to prevent additional sperm from binding and fusing with the egg, thus preventing polyspermy.

Question 9

Which ion controls the slow block to polyspermy?&#10;A) Sodium&#10;B) Calcium&#10;C) Potassium&#10;D) Chloride

Accepted Answer

Calcium ions (Ca2+) control the slow block to polyspermy by causing cortical granules in the egg to release their contents into the space between the plasma membrane and the vitelline layer, altering the egg's coat and preventing additional sperm from binding.

Question 10

The presence of an SRY sequence in a mammalian genome causes the degradation of which of these structures?&#10;A) Wolffian duct&#10;B) Vas deferens&#10;C) Sertoli cells&#10;D) M&#252;llerian duct

Accepted Answer

The SRY gene, found on the Y chromosome, triggers the development of male physical traits. One of its effects is to promote the degradation of the Müllerian duct, which in the absence of SRY, would develop into female reproductive structures.

Deck 9: Germ Cells, Fertilization Sex