Biology 441, Spring 2013 Review for Final Exam


Last set of review questions

The final exam will be cumulative (in the sense of including questions from all parts of the course); So please study the previous lists of review questions, in addition to this new one.


For every organ and cell type of the body, you should know which of the 3 primary germ layers it is derived from, and likewise which of the subdivisions of this germ layer (for example: neural tube ectoderm) that is is derived from.

What is metamorphosis?

What are at least three different examples of metamorphosis (e.g. caterpillars change into what? Plutei change into what? Tadpoles change into what?)

What are at least 7 different changes that occur when a tadpole metamorphoses into a frog?

What is thyroxine?

What is ecdysone?

What is meant by molting, in relation to the growth of insects and other arthropods?

What is Juvenile Hormone?

How does Juvenile Hormone participate in the control of molting and metamorphosis of insects?

You should be able to describe or identify the following:

    Spina bifida
    Cleft palate
    Cleft lip
    Oropharyngeal membrane

What is a teratogen, and why should we expect that any chemical which is a morphogen will also be a teratogen?

What is trisomy?

Why is trisomy for larger chromosomes more likely to result in miscarriage or stillbirth than trisomy for the smallest chromosome?

Compare and contrast the reversibility of differentiation in animal cells versus plant cells.

What is a specific example of regeneration in which cells convert from one cell type to another?

What is at least one example in which regeneration does NOT depend on cells changing from one cell type to another?

* What would be some medical uses of a method that could cause cells of one differentiated cell type to convert to cells of a different cell type?

* Invent a mechanism that might explain the near-irreversibility of cytodifferentiation of animal cells.

* Extend your hypothetical mechanism to explain why animal cells cannot simultaneously belong to two differentiated cell types (i.e. express two different sets of luxury genes; e.g. simultaneously be a muscle cell and also a lymphocyte).

* Further extend your hypothesis to relate the molecular mechanism(s) of differentiation to the branching pattern of ectoderm, mesoderm and endoderm, followed by the subdivision of ectoderm into neural tube, neural crest, etc., subdivision of the mesoderm into notochord, somites, intermediate mesoderm & lateral plate mesoderm, subdivision of somites into dermatome, etc.

Antibodies are synthesized by which particular kind of cells?
T-lymphocytes bind to antigens at a binding site called what?
Suggest two major reasons why it's necessary that the great majority of lymphocytes undergo apoptosis.

Which of the following is closest to the reason that people don't normally make antibodies against their bodies' own antigens?

    a) Because every molecule in the body is labeled with special molecules that are special for them, and which lymphocytes recognize as "self", in the sense of avoiding attacks or binding to any molecule with that "self" label.

    b) Genetic linkage prevents anybody who inherits the gene for the A antigen from also inheriting the gene for antibodies that bind to the A antigen, and likewise for every combination of antigens and antibodies.

    c) Transcription of RNA is selectively inhibited for any antibody whose binding site would fit any of a person's own antigens.

    d) Because some mechanism weeds out those V, D and J regions of DNA that would code for antibodies that would fit any of that person's own antigens.

    e) Some mechanism selectively kills, inactivates or sequesters all B and T lymphocytes whose combinations of V, D and J regions of DNA actually do code for antibodies (or T-cell receptors) that actually do fit any of that person's own antigens.

    f) When antibodies bind to antigens that are present in large enough amounts, then those antibodies are quickly filtered out of the blood.

    ) Some other mechanism? Put it in your own words.

Antibodies are synthesized by which particular kind of cells?
T-lymphocytes bind to antigens at a binding site called what?
Suggest two major reasons why it's necessary that the great majority of lymphocytes undergo apoptosis.
(hint: Remember the randomness of the VDJ recombination of lymphocyte DNA! This is important!)

Explain each of the following newly-invented-just-for-this-exam (but really might work!) cures for cancer (your explanations can include criticisms or means to improve them).

    a) A chemical analog to tyrosine which is not poisonous itself, but is converted into a poison when enough of its many -OH side chains get phosphorylated (covalently bonded to a phosphate group). Hint; What sort of molecular abnormality could attach phosphates to them?).

    b) A twenty-some amino acid peptide that can be cleaved in two to produce any amino acid sequence very similar in conformation to an amino acid sequence found in vaccines against measles, polio or whooping cough. c) An analog to GTP (guanosine triphosphate) that binds to Ras proteins, but which in this bound state stimulates apoptosis unless its third phosphate is quickly cleaved off.

    d) A chemical that de-represses caspase enzymes in response to disorganization of the cytoskeleton.

    e) A chemical that inhibits one or more of the cell cycle checkpoints, thereby allowing mitosis to continue even if the chromosomes are not aligned on the spindle, or that allows DNA synthesis to begin regardless of damage to the DNA.

    f) A chemical that kills cells in which the bcl-2 protein somehow becomes too concentrated.

    g) A chemotactic attractant that stimulates migration of cancerous cells toward the direction of increased concentration of this substance. h) A drug that speeds up DNA synthesis and/or mitosis more in cancer cells than in normal cells.

    i) A drug that slows down DNA synthesis and/or mitosis more in normal cells than in cancer cells.

    j) A drug that creates holes through plasma membranes wherever certain growth factor receptor proteins are over-active.

Please invent several more new methods for taking advantage of (1) The abnormalities observed in cancer cells, (2) The biochemical effects of oncogenes, (3) And the mechanism of apoptosis for the purpose of selective killing of cancer cells, while harming normal cells as little as possible.

Describe at least three different birth defects that occur in humans that are caused by failure of epithelia to fuse with each other.

For each of these three, what spaces fail to become separated from each other?

One of these birth defects can be detected in embryos by presence in the amniotic fluid of certain proteins that are normally found only in cerebrospinal fluid. Can you explain this by a drawing of the location of the neural tube relative to the amnion.

What are caspases?

Where are they normally located?

Are they enzymes?

Why are their active sites normally blocked?

What is metastasis?

"Septal defects" are a serious and important category of birth defects of the heart, in which a hole remains through which blood can flow freely from one ventricle to the other.

Would you expect this to cause any harm before birth? (Hint, no!) Explain why or why not.

If the hole is not closed by surgery, what bad results will there be?

*) Suggest a reason or reasons why the muscular walls of the two ventricles have the same thickness until birth, but then the muscular wall of the left ventricle becomes much thicker.

*) What does it suggest to you that if the foramen oval remains open, then one effect is that this difference in thickness and strength (between the left and right ventricles) does not occur (i.e. the continue to have the same muscular strength and thickness

You should be able to write a few sentences about each of the following:

    thymus gland
    t-cell receptor
    generation of diversity
    autoimmune disease
    immune tolerance

Why do we need an immune system? What two differentiated cell types do the attacking?
Do they ever attack anything other than germs? 2 examples.
An "antigen" is any molecule that is selectively bound to by (what parts of?) proteins called what?
Which are made and secreted by what differentiated cells?
Virus-infected cells are induced to do what?
This is accomplished by what other differentiated cell type?
The "Generator of Diversity" accomplishes what?
What is unusual about the genes for antibody binding sites?
* In your opinion which is more surprising? That people EVER make anti-self binding sites, or that this doesn't happen much more frequently? Please explain your reasons for this opinion.

Describe the structure of arteries, veins and capillaries. How do they differ from each other?
Where are blood cells formed in an embryo? Why is this not the same location as their site of formation in adults?
What is fetal hemoglobin? What would happen if an adult continued to make it?
What are blood islands?
Describe the circulatory system in an early mammalian embryo, and compare it to the circulation of an adult fish.
Draw a diagram of blood flow before and after birth, and answer the following questions (from the web page on heart and kidney development):

    a) Which direction does blood flow through the foramen ovale, prior to the moment of birth?
    b) Which direction does blood flow through the ductus arteriosus before birth?
    c) Why doesn't the blood flow in the other direction in the foramen ovale?
    d) Why doesn't it flow in the other direction in the ductus arteriosus?

From what do the mammalian oviducts, fallopian tubes and uterus develop?

What might be different about salamanders that allows them to regenerate entire limbs? How would you go about trying to identify a substance involved in the control of this process, either by stimulating regeneration in salamanders, or prohibiting it in other vertebrates?

What are glial cells? What are Schwann cells?

How do axons and dendrites differ from each other?

What very important scientific method was developed by Ross Harrison, and what connection did it have to nerve cell growth?

What are motor nerves? autonomic nerves? sensory nerves? spinal sensory ganglia? ganglion cells?

When do nerve cells replicate their DNA?

Describe the composition of the brain and spinal cord.

What is the optic tectum? What is a neural projection? The retino-tectal projection?

What are ephrins? Describe how they are thought to work in formation of neural connections.

What are the three ways in which human identical twins are formed? Which can lead to formation of conjoined twins?

Propose some new methods for treating cancer, different from those now being used:

What are the major weaknesses of current methods of cancer chemotherapy? (Specificity, or lack of specificity? Side effects? Failure to take advantage of apoptosis? The fact that many cancers are slow-growing?

What fact or phenomenon that you learned about in this course surprised you most? Briefly describe the phenomenon and the evidence supporting its occurrence.



What is meant by the words haploid, diploid, tetraploid, and trisomic?

Describe the sequence of events that occur when a newt or other salamander regenerates one of its legs.

What is a blastema? What is dedifferentiate? When salamanders regenerate the skeleton and musculature of one of their legs, do any of the previous chondrocytes redifferentiate as muscle cells?

What is the experimental evidence for or against this fact?

Likewise, do any of the previous muscle cells redifferentiate as skeletal cells? And what is the evidence?

Discuss why, or why not, you would have expected these results, drawing on several particular facts and principles that you have learned in other parts of the course.

What are some facts that would have led you to expect these results?

Conversely, what facts would have led you to expect that dedifferentiated blastema cells would re-differentiate into whichever differentiated cell type is needed at each particular location.
(Hint: You can use Wolpert's concept of positional information in your answer to this question).

In what ways is what happens in salamander limb regeneration like what happens when dissociated sponge cells sort out?

In what ways is salamander limb regeneration like when happens when embryonic vertebrate cells are dissociated and randomly mixed?
(Hint: How are the behaviors of cartilage and muscle cells similar or different in sorting out as contrasted with what happens is salamander regeneration of limb skeleton and musculature)

Compare the limb bud development with development of the entire animal of sea urchins, frogs, and mammals.
(Hint: What happens when limb buds, and embryos are split in two, of fused side by side?)

Also, compare or contrast the development of anterior-posterior axes in limb buds as compared with whole embryos.

How does sex determination work in Drosophila, and how is it different from sex determination in mammals?
(Hint: both have X and Y chromosomes but the mechanisms by which sex is determined are very different. Be prepared to explain this.)


Some of these questions pertain to earlier parts of the course.

Teeth develop by reciprocal induction of cells from which two subdivisions of what germ layer? (Hint, one starts with an S)

What are the two main pieces of evidence that aggregating Dictyostelium amoebae attract each other by chemotaxis?

What do embryologists mean by "epiboly"? And what is one specific example?

Name the four extraembryonic membranes in human and bird embryos (in any sequence) and the function of each, and then name the two extraembryonic membranes in teleost fish embryos.

Turing's "Reaction Diffusion mechanisms" are related to "Curie's Principle" in what way?

Suppose that the wall (septum) between the right and left ventricles of a baby's heart completely failed to develop: When would problems develop, and why not until then?

What is an Apical Ectodermal Ridge, and what different anatomical abnormalities can you produce by surgical removal, or by surgical transplanation of this structure?

What is "Wolffian lens regeneration" and why is it especially interesting?

What is the "Wolffian duct"? From what does it develop? What function(s) does it serve in embryonic humans, and what function (if any) does it serve after birth?

Imagine that evolution had produced mammals in which the blood supply to and from the placenta were by means of branches off of the pulmonary arteries and veins (the ones that carry blood from the heart to the lungs and back again). How would this alter the changes in blood flow that occur at the time of birth?

Suppose that a developmental biologist is trying to find as many different mutant zebra fish as possible which are blind because the optic nerve does not connect normally, or at all, to the optic tectum: What key question can be answered by means of a really complete collection of such fish?

Draw an early limb bud, and sketch graphs of the curvatures of its surface along the dorso-ventral axis
(Hint: they are sometimes described as "paddle shaped")

Imagine an experiment in which somebody takes an early snake embryo, soaks a plastic bead in fibroblast growth factor, and then surgically implants this bead into the somatic layer of the lateral plate mesoderm, and the snake then develops a leg, with fingers and claws, at the location where the bead was implanted! What might this result tell you about the molecular changes in evolution by which snakes stopped developing legs? (Specifically, as opposed to what other molecular changes that could have produced this same result).

List and briefly define at least 4 different categories of guidance mechanisms that have been shown experimentally to be able to guide axon outgrowth, or other examples of cell locomotion.

What is the dermis, and what does it develop from?

The fruiting bodies (stalks and masses of spores) of Dictyostelium have what different kinds of symmetry? (Don't forget another kind of symmetry: between small and large ones!)

Why does a soap bubble, floating in space, have spherical symmetry?

If one soap bubble has twice the diameter as another one, compare the curvatures of the surfaces of the large bubble versus the small one, and compare the air pressures inside each.

Why can rubber balloons have so many more complicated shapes than soap bubbles?

What causes conjoined twins?

Suppose that at the one cell stage of an embryo, two chromosomes happen to break at locations between promoter regions of certain genes and the parts of those genes that code for the protein, and then each chromosome fragment rejoins incorrectly with the DNA of the other chromosome. If the genes are normally transcribed only in differentiated cells (and NOT in the same cell type), then what will happen as a result of this genetic transloation?

If Dolly the sheep had developed from an oocyte injected with a nucleus taken from a lymphocyte (instead of a nucleus from a mammary cell), then supposing she really did develop into a sheep, what would have been the most important and interesting abnormality of this sheep?

Explain the different between tensor, vector, and scalar properties, with an example of each.

Why are two sperm just as bad as no sperm?

Why do kidneys and hearts develop so much earlier than brains or legs? (or do they?)

Imagine, draw and describe in some detail the embryonic development of a "science fiction" organism (perhaps on another planet) in which the circulatory system progressively has three different hearts, analogous to the way in which human embryos have three different pairs of kidneys.



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