Genetic Basis of Development

Question 1

What four stages make up embryonic development?

Answer 1

Fertilization: combination of sperm and egg nuclei and egg activation
Cleavage: Rapid cell divisions without substantial growth in size to generate a multicellular embryo
Gastrulation: mass cell movements to generate three germ layers
Organogenesis: localized changes in tissue and cell shape

Question 2

What 3 things result in transofrmation from zygote to an adult?

Answer 2

Cell Division, Cell Differentiation, and Morphogenesis

Question 3

Cell Differentiation

Answer 3

The process by which cells become specialized in structure and function

Question 4

Morphogenesis

What are the two main stages?

Answer 4

The physical processes that give an organism its shape constitute morphogenesis.
1. Gastrulation
2. Organogenesis

Question 5

What are cytoplasmic determinants?

Answer 5

Cytoplasmic determinants are maternal substances in the egg that influence early development. As the zygote divides, cells have different determinants, leading to differential gene expression.

Question 6

Aside from cytoplasmic determinants, what is the other important source of developmental information in a cell? Name and describe the process by which cells tell other cells to become a certain kind of cell.

Answer 6

Environment around the cell, especially other cells. Through INDUCTION, signal molecules from embryonic cells cause transcriptional changes in nearby target cells. (Muscle cells can tell other cells to become muscle cells).

Question 7

What is determination? How does this process work to determine a Myoblast using a master regulatory gene?

Answer 7

Determination is the process by which a cell is irreversibly committed to becoming a specific kind of cell.

A myoblast is a cell that produces muscle-specific proteins and forms skeletal muscle cells.
A master regulatory gene, myoD produces a myoD protein, that acts as a transcription factor. This transcription factors induces transcription of ITSELF, the myoD gene, as well as enhancers of various target genes. This results in the production of myosin, other muscle proteins, and proteins that block the cell cycle.

Question 8

Pattern formation

Answer 8

Pattern formation is the development of a spatial organization of tissues and organs. In animals, pattern formation begins with the establishment of the major axis. In drosophila, cytoplasmic determinants determine the axes before fertilization (morphogens)

Question 9

What is the bicoid gene? What is the consequence of an embryo whose mother has no functional bicoid gene?

Answer 9

The bicoid gene is a morphogen & maternal effect gene that affects the front half of the body. An embryo whose mother has no functional bicoid gene has two posterior structures at both ends of the body (lacks front half of body).

Question 10

Morphogen Gradient Hypothesis

How does this relate to bicoid?

Answer 10

The morphogen gradient hypothesis states that gradients of morphogens establish an embryo’s axes and other features.

High concentration of bicoid usually occurs at the anterior end of the drosophila, telling the body where to put the head.

Question 11

Cleavage

What process does it follow? What is it? What does it form?

Answer 11

Fertilization is followed by a process known as cleavage, where there is a series of rapid cell divisions without actual growth.

This splits the cytoplasm into many smaller cells called blastomeres, which make up the blastula ( a ball ), with a fluid-filled cavity called the blastocoel.

Question 12

What is yolk and how does it influence the pattern of cleavage?

Answer 12

Yolk is concentrated, stored nutrients in an egg. The vegetal pole has more yolk than the animal pole and creates the animal/vegetal hemispheres. Yolk slows down cleavage.

Division is more rapid in the animal hemisphere because there is less yolk, and thus the animal hemisphere has smaller cells.

Question 13

What is morphogenesis and what two processes make it up?

Answer 13

Morphogenesis is the process by which cells occupy their appropriate location
It involves:
1. Gastrulation: the movement of cells from the blastula surface to the interior of the embryo
2. Organogenesis: the formation of organs

Question 14

Describe gastrulation in frogs

Answer 14

Frog gastrulation begins when cells on the dorsal side begin to invaginate, forming a crease where the gray crescent formed. The part above this crease is the dorsal lip of the blastopore.

Cells move from the surface into the embryo by a process called involution. These cells become the endoderm and mesoderm and the surface embryo cells become the ectoderm.

Question 15

What does the ectoderm become in frogs? (4)

Answer 15

• Epidermis of skin and its derivatives
• Nervous and sensory systems
• Pituitary gland, adrenal medulla
• Jaws and Teeth

Question 16

What does the mesoderm become in frogs? (5)

Answer 16

• Skeletal and muscular systems
• Circulatory and lymphatic systems
• Excretory and reproducive systems
• Dermis of skin
• Adrenal Cortex

Question 17

What does the endoderm become in frogs? (3)

Answer 17

• Epithelial lining of digestive tract
• Epithelial lining of respiratory, excretory, and reproductive tracts and ducts
• Thymus, thyroid, and parathyroid glands

Question 18

What germ layer does the notochord and neural plate form from?

Answer 18

Cells from the mesoderm form the notochord, then the mesodermal cells release a signal that causes the ectoderm to become the neural plate.

Question 19

How is the neural tube formed and what does it become? What are neural crest cells?

Answer 19

The neural tube is formed when the neural plate curves inward. The neural tube, then, becomes the CENTRAL NERVOUS SYSTEM (brain and spinal cord).

Neural crest cells form along the neural tube of vertebrates and form various parts of the embryo (nerves, teeth, skull bones)