Bio Lecture 7: Part 1

1. Name the (4) main stages of development.

Cell Division, Growth, Maturation, Senescence

FertilizationCleavageGastrulationOrganogenesis

Embryogenesis, Differentiation, Maturation, Regeneration

Prenatal, Postnatal, Adolescent, Adult

The correct answer includes the main stages of development from the initial fertilization to the formation of different organs in the organism's body.

Explanation

The correct answer includes the main stages of development from the initial fertilization to the formation of different organs in the organism's body.

2. What happens during Fertilization?

The testes produce sperm continuously throughout a person's life.

The egg is released from the body during menstruation.

The sperm and the egg meet to produce the zygote

Fertilization occurs in the lungs.

Fertilization is the process where the sperm and the egg meet in the fallopian tube to form a zygote, which then develops into an embryo. The other three options are incorrect as they do not accurately represent the process of fertilization.

Explanation

Fertilization is the process where the sperm and the egg meet in the fallopian tube to form a zygote, which then develops into an embryo. The other three options are incorrect as they do not accurately represent the process of fertilization.

3. What is the principle purpose of Cleavage?

To store energy reserves for the developing organism.

Cell division occurs to produce the blastula. The blastula is the hollow ball of cells from which the organism develops.

To form specialized tissues and organs in the organism.

To create new genetic material for the organism.

Cleavage is the rapid cell division that occurs in the early stages of embryonic development, leading to the formation of the blastula. The blastula is crucial for further development of the organism.

Explanation

Cleavage is the rapid cell division that occurs in the early stages of embryonic development, leading to the formation of the blastula. The blastula is crucial for further development of the organism.

4. What occurs during Gastrulation?

Development of the skeletal system.

During gastrulation, formation of germ cell layers occurs as well as the primitive gut. Gastrulation is a morphogenetic process that involves a dramatic rearrangement of the cells of the blastula.

Growth of the nervous system.

Formation of the circulatory system.

Gastrulation specifically refers to the process of germ cell layer formation and primitive gut development, not the growth of the nervous system, formation of the circulatory system, or development of the skeletal system.

Explanation

Gastrulation specifically refers to the process of germ cell layer formation and primitive gut development, not the growth of the nervous system, formation of the circulatory system, or development of the skeletal system.

5. What happens during Organogenesis?

The formation of organs and tissues.

The production of red blood cells in the bone marrow.

The absorption of oxygen in the lungs.

The process of digestion and absorption of nutrients.

Organogenesis is the process in embryonic development where organs and tissues are formed, not to be confused with other bodily functions such as digestion, blood cell production, or oxygen absorption.

Explanation

Organogenesis is the process in embryonic development where organs and tissues are formed, not to be confused with other bodily functions such as digestion, blood cell production, or oxygen absorption.

6. How is the Anterior-Posterior axis determined and when does it occur in many species?

The Anterior-Posterior axis is determined by external factors after fertilization in most species.

The Anterior-Posterior axis is a randomly established orientation in developing embryos.

The Anterior-Posterior axis are determined by the uneven distribution of substances in the cytoplasm including specific mRNAs, proteins and yolk. The combination of all these cellular materials are called cytoplasmic determinants.
In many species (not including humans) this determination of anterior-posterior axis occurs prior to fertilization of the egg by the sperm.

The Anterior-Posterior axis is determined solely by the genetic makeup of the offspring.

7. Define the vegetal pole and describe its appearance.

The vegetal pole is defined as the side of the zygote with a greater concentration of the yolk (stored nutrients)This pole is characterized by its yellow color because of lack of dark pigment granules.

The vegetal pole is the side of the zygote with a greater concentration of the eggshell.

The vegetal pole is the side of the zygote with a greater concentration of the sperm entry point.

The vegetal pole is the side of the zygote with a greater concentration of the cytoplasm.

The vegetal pole is characterized by its yellow color due to the lack of dark pigment granules, not due to eggshell, sperm entry point, or cytoplasm concentration.

Explanation

The vegetal pole is characterized by its yellow color due to the lack of dark pigment granules, not due to eggshell, sperm entry point, or cytoplasm concentration.

8. What is the animal pole and how is it distinguished?

The animal pole is the side of the zygote where the yolk is most concentrated.

The animal pole is defined by the side of the zygote where the yolk is less concentrated, and is also the site of where the polar bodies of oogenesis bud from the cell.The animal pole is characterized by its dark color as a result of a high concentration of dark pigment granules in the region.

The animal pole is characterized by a light color due to a lack of pigment granules.

The animal pole is located at the center of the zygote.

The animal pole is defined by its distinct characteristics, including the concentration of yolk, the presence of polar bodies, and the dark color due to pigment granules.

Explanation

The animal pole is defined by its distinct characteristics, including the concentration of yolk, the presence of polar bodies, and the dark color due to pigment granules.

9. When is the Dorsal-Ventral Axis established?

The Dorsal-Ventral Axis is established at birth.

The Dorsal-Ventral Axis is established during embryonic development.

The Dorsal-Ventral Axis is established before fertilization.

The Dorsal-Ventral Axis is established after fertilization

The Dorsal-Ventral Axis is a critical embryonic axis that is established after fertilization and plays a key role in body patterning and development.

Explanation

The Dorsal-Ventral Axis is a critical embryonic axis that is established after fertilization and plays a key role in body patterning and development.

10. Why does the cytoplasm rearrange after fertilization and what does this rearrangement form?

The rearrangement is random and has no specific purpose.

The rearrangement forms new organelles within the cytoplasm.

After fertilization, the plasma membrane and cortex rotate towards the point of sperm entry.(see picture) this occurs so that the point of entry of the sperm is directly parallel with the regions defining the vegetal pole (yellow) and the animal pole (blue).
The rearrangement of the cytoplasm causes the exposure of the grey crescent.

The cytoplasm rearranges to form a protective barrier around the egg.

After fertilization, specific rearrangement of the cytoplasm occurs to align crucial regions of the egg, not randomly. The rearrangement is not for protective purposes or for forming new organelles.

Explanation

After fertilization, specific rearrangement of the cytoplasm occurs to align crucial regions of the egg, not randomly. The rearrangement is not for protective purposes or for forming new organelles.

11. What does the grey crescent define?

The grey crescent, formed from the rearrangement of the cytoplasm, defines the dorsal side of the embryo

The grey crescent defines the ventral side of the embryo.

The grey crescent defines the left side of the embryo.

The grey crescent defines the right side of the embryo.

The grey crescent is a significant feature during early embryonic development and specifically marks the dorsal side of the embryo. This plays a crucial role in establishing the body axis and determining the positioning of organs and structures during development.

Explanation

The grey crescent is a significant feature during early embryonic development and specifically marks the dorsal side of the embryo. This plays a crucial role in establishing the body axis and determining the positioning of organs and structures during development.

12. How is the dorsal side of the embryo determined in terms of cytoplasmic determinants?

The way in which different proteins, kinases and inhibitors are distributed within the cell lead to different cellular processes that help to define the dorsal side of the embryo.

By the physical size of the cell and its organelles.

Through the specific positioning of DNA and RNA molecules within the cell.

The process involves the interaction of certain proteins, kinases, and inhibitors within the cytoplasm.

Two unique chemical compounds secreted by neighboring cells signal the dorsal side.

The dorsal side of the embryo is determined by the distribution of various proteins, kinases, and inhibitors within the cell, which in turn initiate specific cellular processes leading to the differentiation of dorsal structures during development.

Explanation

The dorsal side of the embryo is determined by the distribution of various proteins, kinases, and inhibitors within the cell, which in turn initiate specific cellular processes leading to the differentiation of dorsal structures during development.

13. On slide 5, what did the blue, red, and peach colors represent?

Yellow = Ribosomal RNA synthesis

The blue represent GSK-3 which is a protein kinase. The protein kinase phosphorylates the peach
The red represents a GSK-3 inhibitor which stops the phosphorylation of the peach
The peach represent b-catenin, a component of cell-cell signaling that defines the dorsal side as development proceeds

Green = DNA replication

Purple = Lipid metabolism

The blue, red, and peach colors represent specific components and interactions in cell-cell signaling, distinguishing them from unrelated processes such as DNA replication, ribosomal RNA synthesis, and lipid metabolism.

Explanation

The blue, red, and peach colors represent specific components and interactions in cell-cell signaling, distinguishing them from unrelated processes such as DNA replication, ribosomal RNA synthesis, and lipid metabolism.

14. Where are the blue, red, and peach colors located respectively in the zygote and why is this significant?

In the zygote, the peach b-catenin is located near the animal pole for structural support.

In the zygote, the red GSK-3 inhibitors are located near the vegetal pole. They are located here to stop the phosphorylation action of the blue GSK-3 kinases of the peach b-catenin. This is important because the presence of b-catenin defines the dorsal end.
Conversely, there is a low concentration of the red GSK-3 inhibitors on the ventral side of the zygote because the cell wants the blue GSK-3 kinases to phosphorylate the peach b-catenin. The phosphorylation of the b-catenin leads to its degradation. Thus, there is no b-catenin on the ventral side (which is good, because b-catenin defines the dorsal side).

In the zygote, the red GSK-3 inhibitors are located near the animal pole.

In the zygote, the blue GSK-3 kinases are located near the vegetal pole to phosphorylate the red GSK-3 inhibitors.

The correct answer explains the specific locations of the colors and their significance regarding the phosphorylation and degradation processes in the zygote, highlighting the importance of the b-catenin in defining the dorsal side.

Explanation

The correct answer explains the specific locations of the colors and their significance regarding the phosphorylation and degradation processes in the zygote, highlighting the importance of the b-catenin in defining the dorsal side.

15. How are the right-left axis determined? When are they determined?

The right-left axis are determined after the anterior-posterior and dorsal-ventral axis are established. The right-left are fixed by the first cleavage, or cell division, which bisects the grey crescent.

The right-left axis are determined randomly and can change throughout the development process.

The right-left axis are determined by the last cleavage, or cell division, that occurs during development.

The right-left axis are determined before the establishment of the anterior-posterior and dorsal-ventral axis.

The correct answer explains the sequence in which the right-left axis is determined in relation to other axes during development. The incorrect answers provide alternatives that are not consistent with the established process of axis determination.

Explanation

The correct answer explains the sequence in which the right-left axis is determined in relation to other axes during development. The incorrect answers provide alternatives that are not consistent with the established process of axis determination.

16. Thus, the grey crescent itself defines ________ and the bisection of the grey crescent defines ________.

Thus, the grey crescent itself defines the lateral side and the bisection of the grey crescent defines top-bottom orientation.

Thus, the grey crescent itself defines the medial side and the bisection of the grey crescent defines inner-outer axis.

Thus, the grey crescent itself defines the dorsal side and the bisection of the grey crescent defines right-left axis.

Thus, the grey crescent itself defines the ventral side and the bisection of the grey crescent defines anterior-posterior axis.

17. During cleavage, the embryo is divided into multiple cells. These cells are called ________.

During cleavage, the embryo is divided into multiple cells. These cells are called Blastomeres.

Gametes

Homunculus

Zygotes

During cleavage, the process involves the division of a fertilized egg into multiple cells known as blastomeres. Blastomeres are essential for the development of a multicellular organism.

Explanation

During cleavage, the process involves the division of a fertilized egg into multiple cells known as blastomeres. Blastomeres are essential for the development of a multicellular organism.

18. What is the hollow structure formed from numerous cells called?

The hollow structure that is formed from the numerous cells is called the Blastula.

Cellular network

Cavity cluster

Spongy body

The correct term for the hollow structure formed from numerous cells is Blastula. While the incorrect answers may sound plausible, they do not accurately describe the specific structure being referred to in this context.

Explanation

The correct term for the hollow structure formed from numerous cells is Blastula. While the incorrect answers may sound plausible, they do not accurately describe the specific structure being referred to in this context.

19. What is the fluid-filled cavity of the blastula known as?

Gastrula

Archenteron

The fluid-filled cavity of the blastula is known as the Blastocoel.

Morula

The Blastocoel is the correct term for the fluid-filled cavity in the blastula stage of development. The Gastrula is the next stage after the blastula, Morula is an earlier stage before the blastula, and Archenteron is the primitive gut formed during gastrulation.

Explanation

The Blastocoel is the correct term for the fluid-filled cavity in the blastula stage of development. The Gastrula is the next stage after the blastula, Morula is an earlier stage before the blastula, and Archenteron is the primitive gut formed during gastrulation.

20. How many rounds of cell division does it take to form a complete blastula?

5 rounds (about 32 cells)

It takes 7 rounds (about 128 cells) to form a blastula formed from blastomeres and complete with a blastocoel.

10 rounds (about 512 cells)

3 rounds (about 16 cells)

The process of blastula formation involves multiple rounds of cell division to generate the necessary number of cells and structure for a complete blastula.

Explanation

The process of blastula formation involves multiple rounds of cell division to generate the necessary number of cells and structure for a complete blastula.

21. Why is it important that the cleavage occurs on the correct plane? (that the grey crescent is divided evenly).

Incorrect Answer C: The grey crescent is just a pigment and does not influence development.

This is very important so that the blastomeres are separated correctly and allowed to develop. If the fertilized egg is not divided evenly, each blastomere does not get the correct cytoplasmic determinants to function correctly.
In the example of the salamander eggs (see image), if the grey crescent is not divided evenly and is only present in one blastomere, the blastomere without the grey crescent will not develop into a full organism.

Incorrect Answer A: The cleavage plane does not affect blastomere development.

Incorrect Answer B: Uneven cleavage results in larger blastomeres, leading to healthier embryos.

The cleavage plane and correct division of the grey crescent are crucial for proper development of blastomeres and ensuring each blastomere receives the necessary cytoplasmic determinants.

Explanation

The cleavage plane and correct division of the grey crescent are crucial for proper development of blastomeres and ensuring each blastomere receives the necessary cytoplasmic determinants.

22. During gastrulation, what are the three germ layers that form in an embryo and where are they located?

Endoderm: lines the embryonic digestive tractEctoderm: outer layer of the embryoMesoderm: partly fills the space between the ectoderm and endoderm layers

Exoderm: inner layer of the embryo

Neoderm: creates the skeletal framework of the embryo

Hypoderm: covers the surface of the embryo

During gastrulation, the three primary germ layers that form are the endoderm, ectoderm, and mesoderm. These layers play crucial roles in the development of different tissues and organs in the developing embryo. The endoderm lines the embryonic digestive tract, the ectoderm forms the outer layer of the embryo, and the mesoderm fills the space between the ectoderm and endoderm layers.

Explanation

During gastrulation, the three primary germ layers that form are the endoderm, ectoderm, and mesoderm. These layers play crucial roles in the development of different tissues and organs in the developing embryo. The endoderm lines the embryonic digestive tract, the ectoderm forms the outer layer of the embryo, and the mesoderm fills the space between the ectoderm and endoderm layers.

23. What is the dorsal lip of the blastopore?

The dorsal lip is the central part of the blastopore.

The dorsal lip is the lower edge of the blastopore.

The dorsal lip is the outermost part of the blastopore.

The dorsal lip is the upper edge of the blastopore.

The dorsal lip of the blastopore refers to the upper edge where gastrulation begins in an embryo. It plays a crucial role in the formation of the three germ layers during early development.

Explanation

The dorsal lip of the blastopore refers to the upper edge where gastrulation begins in an embryo. It plays a crucial role in the formation of the three germ layers during early development.

24. What is the process called when the cell layers on the surface of the embryo roll over the edge of the dorsal lip into the interior of the embryo?

The process of the cell layers on the surface of the embryo rolling over the edge of the dorsal lip into the interior of the embryo is known as involution.
In other words, involution is the creation of the new cavity in the embryo

Proliferation

Eversion

Differentiation

Involution is the specific process described in which cell layers roll over the edge of the dorsal lip into the interior of the embryo. The other options are not correct in the context of this question.

Explanation

Involution is the specific process described in which cell layers roll over the edge of the dorsal lip into the interior of the embryo. The other options are not correct in the context of this question.

25. Define the archenteron.

The archenteron is the appendage that aids in locomotion for the embryo.

The archenteron is the deep tube through the embryo created by invagination and deepened by involution. The end of the archenteron is the blastopore. The archenteron is the primitive gut (connects mouth to anus)

The archenteron is the cavity formed by the union of the ectoderm and endoderm during embryonic development.

The archenteron is the membrane that surrounds the developing embryo in utero.

The correct definition of archenteron involves its connection to the embryo and its role as the primitive gut, which are not characteristics of the incorrect answers provided.

Explanation

The correct definition of archenteron involves its connection to the embryo and its role as the primitive gut, which are not characteristics of the incorrect answers provided.

26. What is the ultimate fate of the blastopore?

The blastopore eventually is sealed by the yolk plug

The blastopore forms the mouth of the organism.

The blastopore remains open throughout development.

The blastopore detaches from the embryo.

The blastopore eventually gets sealed by the yolk plug as part of the development process.

Explanation

The blastopore eventually gets sealed by the yolk plug as part of the development process.

27. Define cell adhesion molecules (CAM).

Cell Adhesion Molecules are a large group of glycoproteins that contribute to cell migration and stabilizing tissue structure. They are cell surface proteins that bind to CAMS on other cells.

Cell adhesion molecules are involved in the process of DNA replication.

Cell adhesion molecules are exclusively found in plant cells.

Cell adhesion molecules are responsible for energy production in cells.

Cell adhesion molecules play a crucial role in cell migration and tissue structure stabilization by binding to other cells. They are not related to energy production, exclusive to plant cells, or involved in DNA replication.

Explanation

Cell adhesion molecules play a crucial role in cell migration and tissue structure stabilization by binding to other cells. They are not related to energy production, exclusive to plant cells, or involved in DNA replication.

28. What is the primary function of Cadherins?

A. Cadherins are responsible for cell movement.

C. Cadherins regulate immune response.

D. Cadherins facilitate cell communication.

Cadherins allow tight adhesion of cells. They are important in the stabilization of the cell structures.Note: They usually require extracellular calcium to function.

B. Cadherins promote cell division.

Cadherins play a crucial role in cell adhesion and tissue organization, aiding in cell-cell adhesion.

Explanation

Cadherins play a crucial role in cell adhesion and tissue organization, aiding in cell-cell adhesion.