Development: is the growth of an individual organism from a simple to a more complex or mature level. A slow process of progressive change

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1 1. Define the following terms (use your own words): development, growth, differentiation, histogenesis, organogenesis, morphogenesis, reproduction, tissue, organ, organ system, and organism. Development: is the growth of an individual organism from a simple to a more complex or mature level. A slow process of progressive change Growth: process of an organism growing organically. Cells divide Differentiation: a process by which a less specialized cell become a more specialized cell type, becomes different during development. Cellular diversity. The generation of specialized cell types. Histogenesis: is the formation of different tissues from undifferentiated cells. Constituents of the endoderm, ectoderm, and mesoderm. The development of tissue cells from an embryonic cell Organogenesis: is the process by which the endoderm, ectoderm, and mesoderm develop into internal organs of the organism Morphogenesis: differentiation and growth of the structure/shape of an organism Reproduction: the process of generating an offspring Tissue: part of an organism consisting of aggregate cells having a similar structure and function Organ: a fully differentiated structural and functional unit that is specialized for a specific function Organ system: is a group of organism that work together to perform a certain task, such as the circulatory system, respiratory system, the nervous system Organisms: a living thing that has the ability to act or function independently 2. Distinguish between growth and differentiation. Give an example where each occurs independently of the other. 3. Explain the following statement: "The entire life history of animals is cyclical." The entire life history of animals is cyclical refers to the fact the life is a cycle with a continuous repetitive process. Fertilization Cleavage Gastrulation Organogenesis Larval Stages Maturity Gametogenesis Fertilization 4. What are the (two) major questions that are addressed by the discipline of developmental biology? How does adult organism develop from one cell? How does adult organism produce another organism? 5. Define (explain what it is) the following terms: chemotaxis, resact, agglutination (of sperm to jelly coat), capacitation, acrosome, bindin, acrosomal filament (process), activation (of the

2 egg), cortex (of an egg), cortical granules, vitelline envelope or membrane, fertilization envelope or membrane, zona pellucid Chemotaxis: is when an organism directs their movement according to certain chemicals in the environment. i.e. the attraction of the sperm towards the egg. It happens as a result of a chemical gradient which is secreted by the egg which the sperm follows. Resact: is a 14amino acid peptide isolated from the egg jelly of the sea urchin which provides the sperm with direction towards the egg. Sperm has receptors for resact, which is why they swim up the gradient. Binding of resact causes the sperm to activate Calcium Channels which is activated by cgmp, made by the sperm. Calcium enters the sperm cell from the seawater, which provides a directional cue to the sperm. The egg releases chemicals for which the sperm follows to get to the egg, known as chemotaxis. Resact, an amino acid peptide binds to the sperm which regulates calcium channels, which increases the concentration of calcium in the sperm cell that are responsible for regulating direction. The fusion of the acrosomal vesicle with the sperm cell and then the extension of the acrosmal process and finally, the digestion of the jelly layer. Agglutination (of sperm to jelly coat): Species-specific binding of acrosomal process to egg surface in sea urchins. Capacitation: maturation of sperm, newly ejaculated sperm cell cannot undergo acrosomal reaction or fertilize an egg. The sperm undergoes a set of physiological changes or molecular events mostly involving sperm cell membrane to which the sperm becomes competent to fertilize the egg. The sperm cell membrane is altered by the removal of cholesterol on the sperm surface are lost. The membrane potential of the sperm cell membrane becomes more negative as potassium ions leave the sperm. This may allow calcium channels to open and let calcium enter the sperm cell. Finally, the outer acrosomal membrane changes and comes into contact with the sperm cell in a way that it prepares it for fusion. Acrosome: is derived the cell s Golgi apparatus and contains enzymes that digest proteins and complex sugars. Can be considered a modified secretory vesicle. The enzymes stored in the acrosome are used to digest a path through the outer coverings of the egg. G actin proteins lie in between the sperm nucleus and the acrosomal vesicle. Bindin: a protein in the acrosomal process which is responsible for recognizing the egg, since it has receptors on the egg cell membrane. They are species specific. Acrosomal filament: the interaction between the sperm and the egg jelly results in the acrosome reaction. 2 components of acrosomal reaction: 1) the fusion of the acrosomal vesicle with the sperm cell membrane, the release of contents of the acrosomal vesicle (exocytosis). 2) the extension of the acrosomal process. The portion of the acrosomal membrane lying directly beneath the sperm cell fuses with the cell membrane to release the acrosomal vesicle contents. The actin molecules assemble to produce microfilaments, extending the acrosomal process outwards. Activation (of egg): The egg jelly is a glycoprotein matrix (a mesh) that is involved in the sperm attraction and activation.

3 Cortex (of an egg): a thin layer of gel-like cytoplasm beneath the cell membrane. Contains high concentrations of globular actin molecules. During fertilization these actin molecules polymerize to form long cables of microfilaments. Cortical Granule: is within the cortex. Are membrane bound, golgi-derived structures contain proteolytic enzymes and are homologous to the acrosomal vesicle of the sperm. There are cortical granules. Vitelline Envelope: the extracellular matrix on the outside of the cell membrane that forms a fibrous mat around the egg and is often involved in the sperm-egg recognition. It is made up of glycoproteins and is essential for the species-specific binding of sperm. Fertilization Envelope: the components of the cortical granule bind to the vitelline envelope. It moves radially away from the egg. It forms cross linkages with adjacent proteins that resist the shear forces of the intertidal waves. It begins to form at the site of the sperm entry and continues its expansion around the egg Zona Pellucida: is made up of three major proteins, ZP1, ZP2, and Zp3 + accessory proteins. A sequential interaction between the sperm and the zona regulate sperm binding. 1) A weak biding to the oviduct derived ligand. 2) Sperm SED1 binds to the ZP complex. 3) Sperm GaIT binds tightly to ZP3 initiationg the acrosomal reaction. This activates a specific G protein in the sperm cell and opens calcium channels which calcium mediates exocytosis of the acrosomal vesicle. 6. List and briefly describe adaptations which increase the probability that a sperm and egg will find one another and that successful fertilization will follow. 7. What role does chemotaxis play in bringing the sperm and egg together? The egg releases a chemical gradient, which the sperm recognizes and follows. Is a result of the attraction of the egg and sperm. 8. What induces sperm activation in sea urchin and what happens in the sperm? Resact which is released from the egg acts as a sperm-activating peptide. One of the roles of egg jelly is to increase the motility of sperm. The sperm-activating peptide causes dramatic and immediate increases in mitochondrial respiration and sperm motility. The increase in cyclic GMP and calcium also activate the mitochondrial ATP-generating apparatus and the dynein ATPase that stimulates flagellar movement in the sperm. 9. What organelle is the acrosome derived from? (What is it counterpart in an egg?) What is the purpose of the enzymes that are located in the acrosome? How are these enzymes released in sea urchin? The acrosome is derived from the Gogli apparatus, it is a modified secretory vesicle. (..) The purpose of the enzymes that are located in the acrosome are used to digest a path through the outer coverings of the egg. They are released in the sea urchin when the sperm comes into contact with the egg jelly. Contact causes the exocytosis of the sperms acrosomal vesicle.

4 10. If intact sperm are injected into a sea urchin egg would they be able to fertilize it? Why, or why not? 11. What two barriers, we have mentioned in class, which prevent the sperm of one species from fertilizing the egg of some different species? Event 1: sperm attraction mostly done by chemotaxis, sperm follows gradient of chemical secreted by egg. Event 2: acrosomal process contains protein bindin which has the receptor on the egg cell membrane (agglutination) 12. What is (are) the role of calcium in fertilization? An increase in the concentration of calcium ions in the sperm activates the cyclic GMP, which gives rise to ATP as a result provides movement of the sperm cell. 13. Describe the process by which the fertilization membrane is formed in the sea urchin (you can use diagrams). Fusion of cortical granule and vitelline envelope components which released contents into space modifying the extracellular space and forming the fertilization membrane. Mycopolysaccharides create an osmotic gradient causing water to enter and expand the envelope. Peroxidase enzymes harden the envelope by cross-linking tyrosine residues. The fertilization envelope starts at the point of sperm entry and expands to surround the fertilized egg. Finally, a hyaline coating is formed around the egg. 14. Briefly describe the origin and functions of the fertilization membrane in sea urchin eggs. The fertilization membrane in sea urchin eggs blocks polyspermy through a process called slow block. 15. Why is it important to prevent polyspermy? What would happen to a sea urchin egg if it became polyspermic? It is important to prevent polyspermy so there are a correct number of chromosomes, incorrect number of centrioles result in aberrant cell divisions. The egg will not survive if two sperms attach to the egg. 3N is impossible because there are way too many chromosomes when it comes to cell division. 16. How is the fusion of the male and female pronuclei different when one compares Sea urchin and mammals? Sea urchins: 1) chemoattraction of sperm to the egg by soluble molecules. 2) Exocytosis of the acrosomal vesicle (acrosome reaction). 3) Digestion of jelly layer. 4) Binding of the sperm to the extracellular (viteline) envelope and passage (digestion) through it. 5) Fusion of the sperm and egg membranes Mammals: 1)Chemoattraction of sperm to the egg by soluble molecules. 2) Binding of the sperm to the extracellular envelope (zona pellucida). 3) Exocytosis of the acrosomal vesicle. 4) Passage of sperm through the zona pellucid. 5) Fusion of the sperm and egg membranes.

5 17. Describe and distinguish between the "fast" block to polyspermy and the "slow" block to polyspermy? Fast block polyspermy is achieved by changing the electrical potential of the egg cell membrane. This happens within 1-3 seconds of fertilization. The resting potential shifts from -70 to +20mV by the influx of sodium ions. Slow block polyspermy is a cortical granule reaction. Cortical granules are activated 1 minute after fertilization. The cortical granules fuse with the egg cell membrane and release their contents into the space between the cell membrane and the vitelline envelope proteins. This clips off bindin receptors and any sperm attached to them. This forms a fertilization envelope.