LCI + Unit Assessment

How many chromosomes are in each daughter cell? [see video]

3

You conduct a study measuring the development of the body axes in the amphibians. You observe axis development with the following characteristics: - Fertilization does not affect axis development - The axis is determined by the egg poles - The axis is established before the dorsal-ventral axis. Which type of axis development did you observe?

Anterior-Posterior; axis development is established during oogenesis.

What is "A" in this figure, and how do you know? [figure in slides]

Archenteron, because this image includes a yolk plug (gastrulation is complete)

Cell division, cell differentiation, and morphogenesis play important roles in animal embryonic development. Which of the following BEST describes the role of cell differentiation?

Causes cell specialization, relying on cell signaling and gene regulation.

Which of the following is TRUE regarding cell differentiation and cell determination?

Cell determination results in the expression of tissue-specific proteins that give cell types their unique structure and function.

Why is cell division alone NOT enough to grow from a single cell to a multicellular embryo (later, adult)?

Cell division alone would just produce a big ball of identical cells

Which of the following BEST describes the conclusion of the study conduted by Hans Spemann (1938)?

Cells with gray crescent cause the development of dorsal features in salamanders

What do you think the relationship is between cleavage and cytoplasmic determinants (CDs)?

Cleavage regulates how cytoplasmic determinants are distributed into blastomeres.

During embryonic development, mammals and reptiles form 4 extraembryonic membranes which provide the "life-support system" for the developing embryo. Why did this adaptation appear in these animals, but not other vertebrates such as fishes and amphibians?

Colonization of land by these animals was only possible after the evolution of structures allowing for reproduction on l

Why are the cortical granules an important structure in sea urchin fertilization?

Cortical granules fuse with the cell membrane, leading to the formation of the fertilization envelope.

Which of the following MOST accurately describes a method of inquiry in science?

Deductive investigations predict results if a certain premise is correct, whereas inductive investigations derive generalizations.

Why do you think each of the daughter cells formed after Meiosis I skip the "S" phase before moving on to Meiosis II?

During "S" phase, DNA is replicated. This is skipped because the sets of chromosomes are halved in meiosis, so replicating DNA would not work.

Consider an E. coli cell that contains the tryp (tryptophan) operon. Assume there is a mutation in the regulatory protein of this operon, that causes the regulatory protein to be continuously bound to the operon, regardless of the presence of tryptophan. Which of the following is TRUE regarding the enzymes encoded by the tryp operon in this cell?

Enzymes needed for tryptophan synthesis would never be produced.

Imagine that you are observing neurulation in a frog. You note that in this developing embryo, NO cells are responding to induction. Which of the following processes would NOT be impacted by this issue?

Formation of the notochord

What do you think the difference is between gene regulation and gene expression?

Gene expression = the flow of genetic information from DNA to protein product. Gene regulation = control/regulation of transcription/translation.

Which of the following is NOT an example of a molecular control that promotes expression of a particular gene?

Heavy methylation of histones

Distantly related organisms have the same basic Homeotic genes in the same relative order. How do you think this relates to evolution?

Homeotic genes evolved very early in the history of life and are clearly valuable to life as they have been unchanged since

Which of the following BEST demonstrates the this idea? "The amount and distribution of yolk in the egg affects cleavage and blastocoel formation"

If the yolk is moderate and concentrated at one pole of the egg, this will lead to asynchronous division.

Which of the following is FALSE regarding gastrulation?

In diploblastic organisms, the blastopore becomes the mouth

Which of the following is NOT an example of how changes in cell movement and shape are important for gastrulation and neurulation?

Induction forms the neural plate

Tryptophan is the signaling molecule. When tryptophan is absent, the regulatory protein is inactive, and the operon is available for transcription. These polypeptides create enzymes for tryptophan synthesis. When tryptophan is present, the regulatory protein becomes active and binds to the operator. This prevents transcription of the genes in the operon. Take a look at the info on the Tryp operon model. Is this an example of negative or positive regulation? How do you know?

Negative, because the end product of the pathway (tryp) serves as a signaling molecule that ultimately represses the pathway.

Do the maternal and paternal homologues have to line up on the same side of the metaphase plate?

No

Which of the following "problems" is NOT something that fertilization can resolve?

Produce many cells quickly to reduce cytoplasmic demand on the DNA

What provides the greatest assurance that fertilization occurs between a sea urchin sperm and egg of the same species?

Recognition of the sperm's bindin proteins by the egg's cell membrane protein receptors.

Which of the following BEST represents an example of an internal control of the cell cycle?

Regulating/changing the amounts of specific clock molecules (cyclin) allow passage through the G2 checkpoint

The egg receptors and sperm bindin proteins are species specific. What does this mean and why does it matter?

Sea urchins are external fertilizers, meaning the egg and sperm fuse outside the organism. Egg and sperm need to recognize the same species in order to fuse and form a functioning zygote of the same species.

Which experiment supports the idea that the dorsal lip contains CD's involved in development of dorsal features (such as the neural tube)?

Spemann and Mangold (1924)

Spemann and Mangold (1924) concluded that the dorsal lip played a role in organizing the dorsal region of the embryo. It is known that the dorsal lip contains "gray crescent". Why is this significant?

The "gray crescent" region in frog embryos contains CDs that signal for the development of dorsal features.

Which of the following is NOT an example of a totipotent cell as discussed in class?

The dorsal lip transplanted into a new gastrula by Spemann and Mangold (1924)

The frog blastocoel is reduced and offset towards the animal pole. Why?

The egg had concentrated yolk towards the vegetal pole, causing asynchronous division and larger, fewer, yolk rich cells at this end.

Which of the following is TRUE regarding these blastomeres and totipotency?

The first two blastomeres of amphibian embryos are totipotent, because they have the potential to differentiate into an entirely new organism

Which of the following is NOT a major difference between the blastula and the gastrula?

The gastrula contains undifferentiated cells.

Assume you are researching negative regulation of the lac operon. You observe that a mutation has take place, which makes it impossible for the regulatory protein to bind to the operator. You observe that this does not happen regardless of whether or not the regulatory protein is active. How will this impact transcription of the genes in this operon?

The genes in this operon will always be transcribed.

Assume you are a researcher investigating the regulation of expression of gene A. You discover that in a particular eukaryotic cell, there is decreased expression of gene A. Which of the following is the BEST example of a possible point of control that could explain this observation?

The histones associated with gene A are unacetylated, resulting in decreased transcription of this gene.

Take a look at these pictures of a chick foot and a duck foot. Which of the following is FALSE regarding how apoptosis relates to this difference in structure? [see video for figures]

The level of apoptosis is GREATER in ducks than in chicks

We see evidence of induction several times during neurulation. Which of the following is NOT an example of induction specifically during neurulation?

The zone of polarizing activity sets of the anterior-posterior axis.

Imagine there was a mutation during frog development that prevented the cortical rotation from occurring. Which of the following is a direct possible outcome of this mutation?

There would be no determined dorsal side.

Consider an E. coli cell in which there is a mutation that makes the regulatory protein for the lac operon unable to assume its active form. Which is true of the enzymes encoded by the lac operon in this cell? Be prepared to explain why!

They will always be produced > there's no protein to turn them off because the reg protein can never be active

Despite differences in organogenesis between vertebrates and invertebrates, there are similarities. Ectoderm rolls into a tube inside the embryo in both types of organisms. In addition the molecular signaling pathways are very similar. What does this suggest evolutionarily?

This suggests a shared evolutionary history, because these features are retained in two distantly related organisms.