1
Q
- Define the following terms (use your own words): development, growth, differentiation, histogenesis, organogenesis, reproduction, tissue, organ, organ system, and organism.
A
- Organism: a living this that has or can develop the ability to act or function independently
- Tissue: part of an organism consisting of an aggregate of cells having a similar structure and function
- Organ: fully differential structural and functional unit in an organism specialized for some particular function
- Organ system: individual organs having specialized functions group into organ system
- Growth: increase in size and mass (can be cell numbers “growth in organism” or cell volume “growth of cell”)
- Development: process of growth differentiation and reproduction of an organism including embryogenesis, postembryonic development, and adulthood. Differentiation= cell becoming specific
- Differentiation: the structural adaptation of an individual cell which enables it to perform a particular fucntion
- Histogenesis: process by which different tissue types from during development
- Organogenesis: the process by which different organs form during deveoplemt
- Morphogenesis: shaping of an organism by embryological processes of differentiation of cells tissues, and organs and the develpemtn of organ systems according to the blueprint of the organism of the potential organism and environment conditions
2
Q
- Distinguish between growth and differentiation. Give an example where each occurs independently of the other.
A
- Growth is the increase in cell mass or size of one type eg. The increase in the cell volume of a single cell
- Differentiation is the change in a single cell to be able to do a particular function eg. morpheogenesis
3
Q
- Explain the following statement: “The entire life history of animals is cyclical.”
A
- The three stages of the animal life cycle:
- Embryogenesis
- Postembryonic development
- Adulthood
- The last stage leads to the first stage when reproduction occurs thus a cycle
4
Q
- What are the (two) major questions that are addressed by the discipline of developmental biology?
A
- How does adult organism develop from one cell?
* How does adult organism produce another organism?
5
Q
- What are the steps of embryogenesis?
A
- Increase the number of cells through cell division
- Increase number of cell types by differentiation
- Generate polarity to allow the establishment of future body axis
6
Q
- The two genetic programs determine/regulate organism’s development. What are they?
A
- Cytoplasmic determinants in the egg
- Genome of the zygote
- Series of cell divisions and uneven distribution of cell determinants in egg– cell differentiation - morpheogenesis
7
Q
- Use your own words to explain a fate map.
A
- Fate map is the location of different types of growth according to location on the embryo
- It is oriented
8
Q
- Generally speaking, each cell will go through three steps in order to achieve it’s own fate. What are those steps? What changes during this process and how?
A
• Specification: cell’s fate is still reversible, can be changed if there are particular changes in environment
• Determination (commitment): cell’s fate is irreversible, cannot be changed by change in environment (even though the determination is not visible i.e. cannot be seen under microscope)
• Differentiation: generation of specialized cell type – fate is absolutely irreversible (change in biochemistry, structure/appearance and function)
The cells gene expression changes during this process. The euchromatin is in its active form and undergoes transcription as the chromosomal material is not strongly strained. The nucleus then becomes heterochromatin because the DNA wraps around histones which is wrapped around proteins, so there is no transcription.
9
Q
- List four differences between epithelial and mesenchimal cells. What is epithelial to mesenchimal transition (in your own words)?
A
- Epithelial
- form sheets connected by junctional complexes
- sheets of cells act as a barrier
- cells (sheets of) move in harmony
- have a clear polar character from one side to another (“top” and “bottom” of the cell are different)
- basal lamina is a foundation; contacts only one surface of the cell
- Mesenchymal
- loosely organized and loosely attached cells
- can (and do) migrate as individual cells
- can also adhere in 3-dimensional clumps
- basal lamina may surround the cells (muscle or fat cells, for example)
- Transition
- The loss of structure in epithelial cells to make cells easier to move by methyl proteases
- Cell-cell junction dissolution
- Loss of apical-basolateral cell polarity
- Actin reorganization
- Increased extracellular matrix proteins
- Migration and invagination
10
Q
- Define morphogenesis. How does morphogenesis happen (i.e. what do the cells do in order for morphogenesis to occur)?
A
- The specification of shaping of an organism by embryological processes of differentiation of cells tissues, and organs and the develpemtn of organ systems according to the blueprint of the organism of the potential organism and environment conditions
- Through
- cell division – direction and extent
- cell growth – some cells become smaller (sperm cells) or larger (egg cells)
- changes in composition of cell membrane and/or in secreted products – eg. extracellular matrix produced by a cell can influence whether (and where) neighboring cells would migrate
- changes in cell shape (can also involve change in cell character through change in cells’ condensation - from epithelial to mesenchymal or the opposite)
- cell movement or migration (individual cells or sheets of cells can move)
- cell death – programmed removal of superfluous cells or entire tissues
11
Q
- 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 egg), cortex (of an egg), cortical granules, vitelline envelope or membrane, fertilization envelope or membrane, zona pellucida
A
- Chemotaxis: Chemical gradient created by egg
- Resect: a sperm attracting and activating peptide which is in the egg jelly of a sea urchin, sperm have receptors for it and swim up the gradient
- Agglutination: sperm binding step of bindin to receptor on egg cell
- Capacitation: set of physiological changes and molecular events: involve sperm cell membrane
- Seminal plasma coatings are removed exposing parts of sperm that can bind to zona pellucida
- Acrosome: at the top of the sperm, the acrosomal membrane fuses with the spermcell membrane and content is released: digestive enzymes
- Bindin: binds to the egg, surrounds the acrosomal filament
- Acrosomal filament: formed by globular actin which aggregates into microfilaments which push the membrane of the sperm cell which contains the bindin
- Activation of the egg: bindin binds to ERB1 receptor on egg cell surface
- Cortex of the egg: 5 um cytoplasmic gel like shell just under the cell membrane, high in globular actin, contain corical granules
- Cortical granules: homologous to the acrosomal vessicle (made by Golgi and contain enzymes which will prevent the additional sperm entry after fertilization).
- Have enzymes which have digestive properties needed for the envelope formation after fertilization
- Vitelline envelople: extra cellular envelope matrix rich in glycoproteins produced by egg
- Fertilization envelope: fusion of cortical granule and vitelline envelope
- Zone pellucida: same as vitelline envelope but in mammals.
12
Q
- List and briefly describe adaptations which increase the probability that a sperm and egg will find one another and that successful fertilization will follow.
A
- Production of excess amount of gametes
- Seasonal reproductive activity and gamete production
- Behavioral (mating) modifications
- External vs. internal fertilization
- (If internal: sperm’s path towards the female reproductive tract)
13
Q
- What role does chemotaxis play in bringing the sperm and egg together?
A
• Creates a chemical gradient which sperm follows to reach egg
14
Q
- What induces sperm activation in sea urchin and what happens in the sperm?
A
• the vitelline envelope induces activation and the sperm undergoes acrosome reaction and creates the acrosomal process which recognizes specific proteins on the egg cell membrane
15
Q
- 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?
A
- membrane fuses with the spermcell membrane and content is released: digestive enzymes
- derived from the golgi apparatus, counterpart in egg is sulfated polysacharides in the egg jelly coat
16
Q
- What do you think: if intact sperm are injected into a sea urchin egg would they be able to fertilize it? Why, or why not?
A
• No it wouldn’t occur as the acrosomal process occurs in the jelly layer, thus the information in the sperm wont be able to come out
17
Q
- What three barriers, we have mentioned in class, which prevent the sperm of one species from fertilizing the egg of some different species? (E.i. what species specific events we have mentioned in class?)
A
- sperm attraction mostly done by chemotaxis ⇒ sperm follow gradient of chemical secreted by egg (sperm attracting and activating peptides, SAP)
- Sperm plasma membrane contains receptors for species specific sulfated polysaccharides from the egg jelly coat
- acrosomal process contains protein bindin which has the receptor on the egg cell membrane, ERB1
18
Q
- What is (are) the role of calcium in fertilization?
A
- Binding of resact causes sperm to activate Ca2+ channel in plasma membrane
- Ca2+ from sea water gets into cell and activates
- mitochondrial ATP-generating apparatus and
- sperm flagellar dynein ATPase
- ⇒ energy for swimming
19
Q
- Briefly describe the origin and functions of the fertilization membrane in sea urchin eggs.
A
- to protect it from other sperm entering
* protection, structural support by the hyaline layer
20
Q
- Why is it important to prevent polyspermy? What would happen to a sea urchin egg if it became polyspermic?
A
- You get abnormal fertilization
- Disintegration, death of embryo
- Incorrect number of chromosomes and centrioles
21
Q
- Describe and distinguish between the “fast” block to polyspermy and the “slow” block to polyspermy?
A
- Fast: change the electrical potential of egg cell membrane
- Slow: use cortical granule reaction- vesicles fuse wit hcell membrane and relase contents between cell membrane and vitelline envelope modifying the extracellular space
- Serine protease digests bindin and clips off extra sperm
22
Q
- How is the fusion of the male and female pronuclei different when one compares Sea urchin and mammals?
A
- The acrosomal reaction occurs in both but only the sea urchin has the acrosomal process
- Mammals undergo capacitation
