MCB305Exam3

You believe that a particular transcription factor is responsible for turning on genes that cause cells in a particular area of an embryo to develop into mouthparts. To test this, you use recombinant DNA technologies to put the coding sequence for the transcription factor under the control of a promoter that allows expression in the tail of the embryo. Is this a Find it, Move it, or Lose it experiment? (Are you interested in how this experiment works out? Stay tuned. . . )

Move it

"Find it" experiments provide what kind of evidence?

correlative

The experiment below shows the results of a Southern and Northern blot. (For those of you who haven't taken 304: A Southern blot is used to detect the presence of DNA sequences in a sample. A Northern blot is used to detect the presence of mRNA in a sample.) The results shown provide support for which of the basic concepts of developmental biology that we covered in week 9?

development proceeds through differential gene expression, NOT differential gene loss

What are the three layers of tissue that form during developemnt?

ectoderm (outer layer) mesoderm (middle layer) endoderm (inner layer)

Germ layers can be distinguished in the early embryo. All the animals we will consider in this course consist of three germ layers. The epidermis of the skin and the nervous system come from which germ layer?

ectoderm and mesoderm

What evidence supports the fact that a human embryo can split into two and develop into twins after day 9 or 10 of development (This is from your reading assignment that was postponed till next week, but I can't change quiz now as some of you have started it, you can find answer in Fig. 12.24)

embryos share a common chorion and amnion

What tissue types does the ectoderm give rise to?

epidermal cells, neurons, pigment cells (melanocytes)

Define teratogen

exogenous agent that causes disruptions

Which of the following would likely NOT affect the first 4 cleavage cycles of an early embryo?

inhibit cyclin D protein

Some scientists hypothesize that genomic imprinting evolved as a competition between males for maternal resources. In support of this hypothesis, we know that paternal imprinting favors (?) offspring, while maternal imprinting favors (?) offspring.

larger, smaller

A transcription unit that is 7,800 nucleotides long may use 1,200 nucleotides to make an mRNA that encodes a protein consisting of approximately 300 amino acids. This is best explained by the fact that

many noncoding stretches of nucleotides are present in mRNA

Which of the following is/are trans-acting factors in gene regulation ? (more than one answer can be correct)

micro-RNAs Repressor proteins Co-activators

A signaling molecule that provides concentration-dependent positional information is called a (?)

morphogen

"Lose it" experiments provide evidence that something is (?) for function.

necessary

"Move it" experiments provide evidence that something is (?) for function.

necessary and sufficient

What tissue types does the mesoderm give rise to?

notochord, bone tissue, tubule cell of the kidney, red blood cells, facial muscles

Suppose you have a powerful microscope that allows you to follow all the cell divisions in a transparent embryo throughout normal embryogenesis, and to keep track of the progeny cells that arise from each cell in the early embryo and see what parts of the animal they become. From these observations alone, you CANNOT determine:

whether signaling from that cell affects the fates of other cells

Define analagous

underlying similarities come from performing similar functions, NOT from a common ancestral structure

Define neurula

- an embryo is the process of folding of the neural plate - neural tube forms

Define somites

- blocks of paraxial mesoderm found on either side of the neural tube - each block forms major compartments

Define somatic cells

- body cells - non-germ cells

Define morphogenesis

- creation of an ordered form - coordinates cell growth, migration, and death

Define chimeric embryo

- embryos made from tissues of more than one genetic cell

Define cytoplasmic determinants

- factors in egg cytoplasm that determine cell fate - often transcription factors

What are the generic stages of development?

- fertilization - cleavage - gastrulation - organogenesis - birth - metamorphosis - gametogenesis

Define zygote

- fertilized egg (diploid) - first developmental stage - divides to produce all cells in the body

Define notochord

- mesodermal rod in dorsal portion of embryo - induces and patterns the nervous system

Define germ cells

- percursor to gametes (sex cells)

Define gastrula

- stage of embryo following blastula gastrulation - contains the three germ layers that will interact to generate the organs of the body

Define morphogenetic determinants

- transcription factors/ mRNAs that will influence the cell's development

Define blastomeres

-A cleavage-stage cell resulting from mitosis - form blastula (initial product of zygote cytoplasm division)

A stem cell can be defined as:

A cell that, when it divides, produces one cell that remains undifferentiated (i.e. a new stem cell) and another cell that differentiates.

What is the difference between a cell that is 'determined' and a cell that is 'differentiated' as a developmental biologist would use the terms?

A determined cell will maintain its specified state whatever its surrounding environment, a differentiated cell will develop specialized structures.

Beckwith-Wiedemann Syndrome is a consequence of

A failure to appropriately methylate the Igf2 gene in a child's maternal genome

What evidence supports the model that the gill arches in fish are homologous to the middle ear bones in mammals?

A fate map of the pharyngeal arches in fish embryos and mammalian embryos.

What is the difference between a specified cell, a determined cell, and a differentiated cell?

A specified cell is capable of autonomously differentiating in a neutral environment, but can have its cell identity altered by being transplanted into a different environment. A determined cell is capable of differentiating autonomously into a single cell type when placed into any environment. A differentiated cell has developed specialized structures and functional properties (it has committed to a fate)

Application of cytochalasin ( inhibitor of actin polymerization) in a single celled embryo will inhibit...

Cytokinesis

Your textbook describes that fibroblast cells can be transformed to induced pluripotent (iPS) stem cells by the introduction of four genes - Oct3/4, Sox2, Kfl4, and c-Myc. If the Oct-4 and SOX2 genes cease to be expressed, which event would most likely take place?

ES cells would begin to differentiate

Your book describes experiments completed by Hans Driesch in the 19th century. He shook sea urchin embryos vigorously at the 4 cell stage to separate the embryos into single cells and allowed them to develop further. What happened and what did he conclude from the results?

Each single cell developed into a normal, albeit small embryo; he concluded that sea urchin development was conditional- determined by cell-cell interactions.

Define blastula

Early-stage embryo consisting of a sphere of cells (blastomeres) surrounding an inner fluid-filled cavity (the blastocoel)

On your last trip to Rocky Point you discover a new species of mud snail. You travel to Rocky Point to study the new species. You perform embryology experiments to study how cells differentiate in the new species. You wish to show that the early embryo undergoes mosaic development and that cleavage of the zygote produces two daughter cells that cannot regulate their cell fate. Which of the following experiments, and results, would demonstrate lack of equivalence of the two cells in the zygote?

Experiment: Isolate the two cells and grow them to the larval stage; Result: the two cells will each develop into only partial larvae.

One of Von Baer's Law states that the early embryo of a phylogenetically derived species is most like the adult of an ancestral species

False

You are interested in the role of a particular protein in determining the germ-line cells of the embryo. You isolate the germ-line cells in embryos at different stages and use a Western blot to determine protein levels for the protein you are interested in. Is this a Find it, a Move it, or Lose it experiment?

Find it

Define transgene

Gene that contains DNA from another species

Which of the following structures or elements involved in gene regulation is a cis-regulatory factor? (more than one answer can be correct)

Promoter Enhancer

Where and how is imprinting established in females?

In the oocyte by the activity of DNA methyltransferases

You are very interested in the development of the nervous system and want to track cells from right after gastrulation through the development of the central nervous system. But the cells are too small to inject at that stage. What could you do?

Inject a caged dye into the egg (single cell), let the embryo develop to a gastrula then photoactivate the dye in the cells you are interested in

From which group of cells in the human embryo are embryonic stem cells derived?

Inner cell mass

You know from the fate map that a specific cell in the 24-cell embryo of the three-horned dinosaur contributes to the third horn. If you culture this cell in isolation, it grows into a third horn. If you transplant this cell to a new location in the embryo, it develops into gut. What can you say about this particular cell in the 24-cell embryo (using the language of an embryologist)?

It is specified to become a third horn

You use a needle to kill a cell in the 8-cell stage in the embryo. After the embryo grows to the larval stage, you examine its form, and find that it is completely missing the structures of the gonad. Is this a Find it, Move it, or Lose it experiment?

Lose it

Define pronuclei

Male/female haploid nucleus within a fertilized eggs that fuse to form the diploid nucleus of the zygote

434 sheep oocytes were used in the now famous experiment that resulted in the birth of Dolly. What did the researchers think was the primary cause of the failure of the other clones? (choose one)

Methylation differences between the chromatin of the zygote and the donor cells derived from the udder cells

One characteristic of embryos that undergo autonomous development is:

Morphogenetic determinants that regulate cell fate are unequally distributed in the egg cytoplasm from the earliest stages

What general principle of developmental biology does the following experiment illustrate? An unfertilized Xenopus egg is irradiated to destroy its nucleus. The nucleus from an adult Xenopus skin cell is injected into the egg. A normal tadpole develops from the egg.

Most of the somatic cells in an organism contain a complete set of genes as the original zygote (genetic equivalence).

Define animal pole

The end of the egg/embryo with low concentration of yolk

Which of the following is NOT true of somatic cell nuclear transfer (SCNT)?

The resulting embryo is genetically identical to the egg donor

What technique was used in Fig. 2E and what conclusion was drawn from the experiment

The scientists used a synapsin:fluochrome reporter and found that neuronal survival was not affected in iPS cells derived from Rett patients relative to controls

In the picture below you can see the results of two transplantation experiments done by Spemann and Mangold. Why are the results different in these two examples?

The transplanted tissue is not yet determined in experiment A.

Define vegetal pole

The yolk-containing end of the egg/embryo

The study of birth defects has taught us enormous amounts about human development. Chapter 1 gives a brief introduction to the effects of thalidomide, a mild sedative given to women to control morning sickness in the early 1960's. If a woman took a thalidomide pill 44 days after her last menstruation, what congenital defects might she have seen in her child?

Very short arms and legs

The strongest evidence that the yellow cytoplasm from the posterior blastomeres of the tunicate embryo harbors determinants for tail muscle cell fate comes from which of the following results?

You can transplant the yellow cytoplasm into other cells and those cells will form tail muscles

Match the type of regulatory control mechanisms in column A to the mechanisms or examples in column B

__RNA transport control__During cleavage of the sea urchin, mRNA for gene x is more abundant in the nucleus than the cytoplasm __post-translational control__Covalent addition of a phosphate group __RNA processing control__Mutations in an intron create a novel transcript with a new function __transcriptional control__Pax 6 mRNA is expressed in the eye, but not the gut __RNA processing control__proteins bound to the 3' UTR of the mRNA

Match the descriptions to the type of cloning

__Therapeutic Cloning__I make embryonic stem cells from a patient with a genetic disease to use these stem cells to test potential drug treatments __Reproductive Cloning__I create a clone of my beautiful dog Cleo and name it Patra

Which molecular genetic technique would you use to:

__isolate mutations in genes involved in early development__EMS mutagenesis __visualize expression of mRNA within an embryo__in situ hybridization __"knock-down" a gene product__RNAi __to "ectopically" express a transcript__create, transform, and express a transgene

In the nematode C. elegans, if one inhibits RNA polymerase II (the polymerase required for transcription) in oocytes, such that the fertilized eggs have no access to this polymerase, the embryos develop to the 100 cell stage and then stop dividing. Interestingly, these embryos are able to initiate the movements of gastrulation (which occurs at the 26-cells stage), and segregate the P granules (cytoplasmic determinants) that define the future germ line correctly. This suggests that:

a and c a) Transcription of the zygotic genome is not required for at least the first 6 cleavages and c) The mother provides sufficient maternal contributions to support early development and segregation of the P granules.

In situ hybridization is an important technique in developmental biology that is used to determine where a particular gene is localized. This method:

a and c: depends on complementarity between a DNA or RNA probe and its mRNA target in the cell AND uses either an enzymatic or fluorescent tag to label the probe

Fig. 1 i in the assigned Marchetto paper demonstrates what important control scientists use when working with iPS cells

a teratoma assay to show the induced cells can give rise to derivatives of all three germ layers

Which of the following statements are true about the 5' and 3' UTRs found on an mRNA? (more than one answer can be true)

a) They can affect the stability of the mRNA b) They can affect the rate of translation

Many experimental results described in Chapter 1 rely on being able to mark cells in the embryo and follow what they become. This technique is called fate mapping. Which of the following do you think would be a requirement for whatever substance you were using to make a fate map?

a, b, d: a) The substance used to mark the cells in the embryo should be a "vital" marker - ie it doesn't kill the cells b) The cell marker would not pass from cell to cell, but should stay only in the "marked" cell and its descendants. d) The substance has a long enough half-life to still be detectable after multiple rounds of division.

Acetylation of histones in the vicinity of a gene causes the gene to be

activated because the histones bind less tightly to the DNA than unacetylated histones.

GFP (green fluorescent protein) is a commonly used reporter gene in developmental biology (remember promoter-GFP constructs from MCB 304?) Reporter constructs using small fluorescent proteins are a useful tool for developmental and cell biology because:

all of the above: a) unlike in situ hybridization, they can be used to follow protein expression in live embryos b) they can be made in different colors, so different proteins can be followed at the same time c) the protein domains are very small and consequently don't usually interfere with normal protein function

The darkly pigmented end of a Xenopus (frog) egg is the (?) pole and will become the future (?) of the frog

animal; anterior

Define Dorso-ventral axes

body axis defining back vs belly

Define antero-posterior

body axis defining head versus tail (mouth vs anus)

The MeCP2 studied in the Marchetto et al. paper assigned and in Chap. 3 of your textbook serves what important function in development (although there is also evidence for other functions not described in your book or the paper)

recognizes methylated CpG nucleotides and recruits chromatin modifying enzymes to repress gene expression

What tissue types does the endoderm give rise to?

stomach cells, thyroid cells, lung cells (alveolar cells)

Define homologous

underlying similarities arise from being derived from a common ancestral structure

The position in an embryo where a morphogen is at its highest level is called (?), and the point at which it is at its lowest level is called (?)

the source; the sink

Cells can be considered totipotent, pluripotent, multipotent or unipotent. How do totipotent and pluripotent cells differ? (chose one)

totipotent cells can give rise to a complete new animal; pluripotent cells can give rise to all the types of cells in the body.