Question 1

Which of the following is a primary external factor in determining the polarity of the body axes in chick embryos?

Accepted Answer

Gravity is a primary external factor influencing the polarity of body axes in chick embryos, affecting how they orient themselves within the egg.

Question 2

Embryonic induction, the influence of one group of cells on another group of cells, plays a critical role in embryonic development. In 1924, Hans Spemann and Hilde Mangold transplanted a piece of tissue from the dorsal lip of an amphibian embryo to the ventral side of another amphibian embryo. The transplanted piece of tissue influences the formation of the notochord and neural tube. If embryonic induction occurred, which of the following observations justifies the claim of embryonic induction?

Accepted Answer

The transplanted tissue from the dorsal lip (a region known for its role in initiating the development of the notochord and neural tube) induced the formation of a second notochord and neural tube on the ventral side, demonstrating the concept of embryonic induction by influencing nearby cells to form structures they otherwise would not.

Question 3

Identical twins are possible in humans because ________.

Accepted Answer

Identical twins result from the separation of early blastomeres, which are capable of developing into complete, individual embryos if isolated. This is due to the totipotency of these cells at early stages of development.

Question 4

Which of the following terms applies to a morphogenetic process whereby cells extend themselves, making the mass of the cells narrower and wider?

Accepted Answer

Convergent extension is the process where a tissue undergoes rearrangement to become narrower (converge) and longer (extend), which is a key mechanism in morphogenesis, the biological process that causes an organism to develop its shape.

Question 5

Which of the following processes reduces the size of a tadpole's tail during metamorphosis?

Accepted Answer

Apoptosis, or programmed cell death, is responsible for reducing the size of a tadpole's tail during metamorphosis. This process allows for the removal of cells that are no longer needed in a controlled manner.

Question 6

Suppose that during gastrulation in humans, a protease (an enzyme that degrades proteins) is present such that the enzymes released by the trophoblast cannot function. What is the most likely immediate outcome of this situation?

Accepted Answer

The trophoblast is crucial for implantation of the embryo into the endometrium by facilitating the invasion of the uterine lining. If proteases prevent the enzymes released by the trophoblast from functioning, the embryo cannot properly implant into the endometrium.

Question 7

Which of the following is most likely to occur if an amphibian zygote is manipulated so that the first cleavage plane fails to divide the gray crescent?

Accepted Answer

The gray crescent area in amphibian zygotes is crucial for normal development, as it contains determinants necessary for the establishment of the body axis. If the first cleavage plane fails to divide the gray crescent, only the daughter cell inheriting the gray crescent will have the necessary components to develop normally, while the other cell will lack these components and will not develop properly.

Question 8

Which of the following are found in developmental precursors to the gonadal tissues of Caenorhabditis elegans?

Accepted Answer

The answer of Which of the following are found in...

Question 9

Which of the following correctly matches an extraembryonic membrane with its function?

Accepted Answer

The allantois is an extraembryonic membrane in many vertebrates, involved in the early fluid exchange between the embryo and the yolk sac. One of its key functions is to act as a site for the collection of waste products from the embryo.

Question 10

Which of the following were Hans Spemann and colleagues studying when they developed the concept of the "organizer" in amphibian embryos?

Accepted Answer

Spemann and his colleagues were studying the dorsal lip of the blastopore in amphibian embryos when they developed the concept of the "organizer." This area is crucial for the initiation of the development of the central nervous system and the organization of the embryo's body plan.

Question 11

In addition to maternal effect genes, paternal effect genes are important for fruit fly development. One such paternal effect gene codes for Sneaky, a protein required for breakdown of the fruit fly sperm plasma membrane that is a critical step for normal embryo development. Suppose that a female fruit fly's oocyte (egg) with a mutation in the bicoid gene is fertilized by a male fruit fly's sperm with a mutation in the Sneaky gene. Both mutations yield nonfunctional proteins. What would be the most likely outcome of this fertilization?

Accepted Answer

The bicoid gene is crucial for the anterior development of the embryo, and the Sneaky gene is necessary for the sperm plasma membrane breakdown, essential for fertilization and subsequent development. Mutations in both genes leading to nonfunctional proteins would prevent normal embryo development.

Question 12

Cells transplanted from the neural tube of a frog embryo to the ventral part of another embryo develop into nervous system tissues. Which of the following claims about the transplanted cells is most consistent with the results?

Accepted Answer

The cells were determined, meaning they were already programmed to develop into nervous system tissues regardless of their new location in the embryo. This determination is consistent with their development into nervous system tissues after transplantation.

Question 13

Which of the following contributions of the extra embryonic membranes was crucial for the colonization of land by vertebrate organisms?

Accepted Answer

Extraembryonic membranes, such as the amnion, provide an aqueous environment that is crucial for the development of the embryo, especially in terrestrial environments where desiccation is a risk. This adaptation was key for vertebrates in colonizing land.

Question 14

Which of the following occurs to the blastocoel during frog development?

Accepted Answer

During frog development, the blastocoel, which is the fluid-filled cavity of the blastula, does not become the archenteron or give rise to the endoderm or placenta. Instead, it is replaced by the expanding archenteron, which is the primitive gut formed during gastrulation.

Question 15

Which of the following is an adult organism that has fewer than 1,000 cells?

Accepted Answer

Caenorhabditis elegans, a nematode, is known for its simple body plan with a fixed number of cells, having fewer than 1,000 cells in its adult form.

Question 16

Researchers were investigating the effects of bicoid in fruit fly development. The gene bicoid controls normal development of anterior structures in flies. In one experiment, they took a normally developing embryo and injected bicoid mRNA into the posterior end of the embryo. What result would they most likely observe?

Accepted Answer

Bicoid is a morphogen that specifies anterior structures in fruit flies. Injecting bicoid mRNA into the posterior end would induce the formation of anterior structures at that site, while the normal anterior end would develop as usual.

Question 17

Just prior to the onset of gastrulation in an embryo, the "organizer" cells are specified. What would you expect in the developing embryo if the specification of these cells were experimentally blocked?

Accepted Answer

Gastrulation is a critical phase in embryonic development where the three primary germ layers (ectoderm, mesoderm, and endoderm) are formed. The "organizer" cells play a crucial role in initiating and directing this process. Blocking the specification of these cells would prevent gastrulation from occurring, leading to a halt in normal development.

Question 18

Which of the following is common to the development of birds and mammals?

Accepted Answer

Both birds and mammals share the developmental feature of forming an embryonic epiblast and hypoblast. These two layers are crucial in early embryonic development, leading to the differentiation of various tissues and organs in both groups.

Question 19

Which of the following processes determines the arrangement of organs and tissues in their characteristic places in 3-D space?

Accepted Answer

Pattern formation is the process that determines the spatial arrangement of organs and tissues in their characteristic places in 3-D space.

Question 20

Which of the following processes will be disrupted if the apical ectodermal ridge is surgically removed from an embryo?

Accepted Answer

The apical ectodermal ridge (AER) is crucial for limb development in vertebrates, providing essential signals that regulate the growth and patterning of the limb bud. Removing the AER disrupts these signals, impairing proper limb formation.

Quiz 46: Development in Animals