Question 1

Which of the following is a morula?

Accepted Answer

A morula is a stage in early embryonic development where a tightly packed ball of cells is formed, typically consisting of 16-32 cells. This stage occurs before the formation of a blastula, where the cells will eventually form a cavity within the ball. Choice A (a fertilized egg) refers to the zygote stage and is a single cell, not a group. Choice B (the group of cells that form the archenteron) refers to the gastrula stage, which is later in development after the morula and blastula stages. Choice D (a hollow sphere of cells) refers to the blastula stage, which comes after the morula stage.

Question 2

Of the choices listed,the first event that occurs during embryonic development is:

Accepted Answer

Cleavage is the first event that occurs during embryonic development. It refers to the rapid series of cell divisions that occur after fertilization, resulting in the formation of a multicellular structure called a morula. This process sets the stage for subsequent development, including germ layer formation, blastula formation, and organogenesis.

Question 3

Which is true regarding somites in an embryo?

Accepted Answer

Somites will become vertebrae. Somites are segmented blocks of paraxial mesoderm that give rise to the vertebrae, ribs, and associated muscles of the body wall.

Answer: B
 Somites are not found inside the notochord. The notochord lies ventral to the neural tube and mesodermal cells migrate from either side of the notochord to form somites.

Answer: C 
 Somites do not form the skull. The skull is formed from neural crest cells that migrate from the neural tube.

Answer: D
 Somites do not form the lungs. The lungs are derived from the endoderm that lines the primitive gut tube.

Question 4

In sea urchin development,the archenteron becomes the:

Accepted Answer

The archenteron is the primitive gut of the embryo. In sea urchins, it becomes the digestive tube.

Question 5

Which of the following is a process by which an initial set of genes turns on a second set of regulatory genes,which eventually turns on a third set of genes?

Accepted Answer

The process described is known as a genetic cascade, where an initial set of genes activates a second set of regulatory genes, which then activate a third set of genes. This is a common process in development and differentiation of cells.

Question 6

Migration of which of the following to different parts of the embryo produces various tissues and organs?

Accepted Answer

Neural crest cells migrate to different parts of the embryo and produce various tissues and organs, including the cranial bones, nervous system, and some muscles.

Question 7

The blastocoel is:

Accepted Answer

The blastocoel is a fluid-filled cavity found within the blastula, an early stage of embryonic development.

Question 8

During which stage of development do cells arrange themselves into three layers?

Accepted Answer

Gastrulation is the stage of development during which cells arrange themselves into three germ layers: the endoderm, mesoderm, and ectoderm.

Question 9

The phase during which embryonic cells arrange themselves into three layers is called:

Accepted Answer

During gastrulation, the blastula (a hollow ball of cells) undergoes a series of complex movements resulting in the formation of three distinct germ layers: the ectoderm, mesoderm, and endoderm. These germ layers give rise to all the tissues and organs of the adult body, a process known as organogenesis.

Question 10

At which of the following levels does bicoid work in fruit flies?

Accepted Answer

Bicoid is a maternal effect gene that controls the anterior-posterior axis of Drosophila embryos. It is responsible for the regulation of development of the head end, middle, and posterior end.

Question 11

Place the following steps of organogenesis in the correct order: (1)neural crest cells break away,(2)neural folds grow into a neural tube,(3)the notochord induces development of the neural plate.

Accepted Answer

The correct sequence for organogenesis, particularly in the development of the nervous system, starts with the notochord inducing the development of the neural plate (3), followed by the neural folds growing into a neural tube (2), and finally, neural crest cells breaking away (1).

Question 12

A difference between a morula and a blastula is that the:

Accepted Answer

A morula is a solid ball of cells, while a blastula forms when a fluid-filled cavity appears in the center of the morula as cells divide and push against each other. So, a significant difference between the two is that the morula lacks a cavity, while the blastula has a cavity in the center. The other options are incorrect.

Question 13

Which cells are most important in initiating the production of bicoid protein?

Accepted Answer

The nurse cells, which are part of the Drosophila melanogaster ovary, are essential for the production of bicoid protein. Bicoid mRNA is synthesized in the nurse cells and then transported into the developing oocyte, where it is translated into protein. This protein gradient plays a key role in establishing the anterior-posterior axis of the embryo. Thus, the most important cells in initiating the production of bicoid protein are the nurse cells.

Question 14

What is the effect of higher concentration of bicoid protein in part of a fruit fly embryo?

Accepted Answer

Bicoid protein plays a crucial role in determining the anterior-posterior axis of the developing fruit fly embryo. A higher concentration of bicoid protein in a particular part of the embryo would cause it to develop into the head end of the organism. Lower concentrations of bicoid protein would lead to formation of more posterior structures. Thus, option C is the correct answer.

Question 15

A basic description of the function of morphogens is that they:

Accepted Answer

Morphogens are signaling molecules that affect the course of local development by controlling the pattern of gene expression and cell differentiation. They provide positional information to cells, directing them to assume different fates based on their location within the developing tissue. Therefore, choice B, which states that morphogens affect the course of local development, is the correct answer. The other choices are not accurate descriptions of the function of morphogens.

Question 16

If an organism is missing the outer layer of skin upon birth,which of the following might be the cause?

Accepted Answer

The ectoderm is the embryonic tissue layer that gives rise to the skin, hair, nails, and nervous system. If the outer layer of skin is missing, it suggests improper development of the ectoderm.

Question 17

Which characteristic is typical of the vegetal pole of an embryo?

Accepted Answer

The vegetal pole typically has a relatively greater proportion of yolk, which is necessary for proper development of the embryo. This is in contrast to the animal pole, which has relatively less yolk and is the site of the development of the nervous system and other important structures.

Question 18

Which of the following is true of the animal pole of a zygote?

Accepted Answer

The animal pole of a zygote is typically characterized by its position relative to the nucleus, being closer to it compared to the vegetal pole. This distinction is important in the early stages of embryonic development, influencing cell division and differentiation patterns.

Question 19

The process of fertilization produces a/an:

Accepted Answer

The process of fertilization occurs when a sperm cell fuses with an egg cell to form a zygote, which is the first stage of embryonic development. The other options (embryo, blastula, morula, and gastrula) are stages that occur after fertilization and are not directly produced by the process of fertilization itself.

Question 20

Which of the following happens first in vertebrate development?

Accepted Answer

The notochord is the first structure to form in vertebrate development and provides the signaling cues for the other structures to form. The development of the neural plate, neural crest, and neural tube all depend on the presence of the notochord.

Quiz 32: An Amazingly Detailed Script: Animal Development