final c & d exam

Living systems are incredibly diverse in size, shape, environment, and behavior. It is estimated that there are between 10 million and 100 million different species. Despite this wide variety of organisms, it remains difficult to define what it means to say something is alive. Which of the following can be described as the smallest living unit?

Cell

Proteins are important architectural and catalytic components within the cell, helping to determine its chemistry, its shape, and its ability to respond to changes in the environment. Remarkably, all of the different proteins in a cell are made from the same 20 __________. By linking them in different sequences, the cell can make protein molecules with different conformations and surface chemistries, and therefore different functions.

Changes in DNA sequence from one generation to the next may result in offspring that are altered in fitness compared with their parents. The process of change and selection over the course of many generations is the basis of __________.

Evolution

Select the option that correctly finishes the following statement: “A cell’s genome _________________.”

 

Contains all of cell's DNA

Which statement represents the cell theory?

 

All cells are formed by the growth and division of existing cells

Which of these cannot be resolved with a conventional light microscope?

 

Ribosome

The __________ __________ is made up of two concentric membranes and is continuous with the membrane of the endoplasmic reticulum.

 

Nuclear envelope

Biologists cannot possibly study all living species. Instead, they try to understand cell behavior by studying a select subset of them. Which of the following characteristics are useful in an organism chosen for use as a model in laboratory studies?

Amenability to genetic manipulation and availability of genetic tools

 

Ability to grow under controlled conditions

 

 

Rapid rate of development and short time to maturity

Where in the cell (i.e., which organelle) does transcription of most messages take place?

Nucleus

The nucleus, an organelle found in eukaryotic cells, confines the __________, keeping them separated from other components of the cell.

Chromosomes

The flow of genetic information is controlled by a series of biochemical reactions that result in the production of proteins, each with its own specific order of amino acids. Choose the correct series of biochemical reactions from the options presented here.

 

replication, transcription, translation

Changes to an organism’s DNA sequence may cause:

 

decreased protein level

 

decreased RNA level

 

changes in protein function

Proteins perform many essential functions in a cell. Which of the following is NOT considered a protein function.

 

providing a template for translation

A neuron and a white blood cell have very different functions. For example, a neuron can receive and respond to electrical signals while a white blood cell defends the body against infection. This is because ______.

 

the neuron expresses some mRNAs that the white blood cell does not.

The distinct characteristics of different cell types in a multicellular organism result mainly from the differential regulation of the _________________.

 

transcription of genes transcribed by RNA polymerase II.

Which of the following statements about differentiated cells is true?

 

Some of the proteins found in differentiated cells are found in all cells of a multicellular organism.

Which of the following steps of gene expression in eukaryotic cells takes precedence over almost all other regulatory mechanisms responsible for turning a specific gene on in a cell?

 

transcriptional control

You are studying a set of mouse genes whose expression increases when cells are exposed to the hormone cortisol, and you believe that the same cortisol-responsive transcriptional activator regulates all of these genes. Which of the following statements below should be true if your hypothesis is correct?

 

The cortisol-responsive genes share a DNA sequence in their regulatory regions that binds the cortisol-responsive transcriptional activator.

There are many important roles for the dynamic nature of proteins in a cell. Which of the following is NOT likely to describe one such reason?

 

Quaternary structures are usually very transient (occur for short periods of time).

Purified antibodies are useful for a variety of experimental purposes, including:

 

Western blotting, immunoprecipitation, and immunofluorescence

You have carried out a genetic screen in a species of fish, and have identified a new gene in this organism. You have cloned and sequenced the gene, but do not know anything about the biochemical function of the gene product. Which of the following is the most sensible next step in order to get clues about the function?

 

Using the BLAST algorithm to scan sequence databases for similar sequences

In situ hybridization and immunostaining both give clues about where (both what cells and where in the cell) a particular gene is expressed. What is the major difference between these two techniques?

 

In situ hybridization detects RNA, while immunostaining detects proteins

The expression of a particular gene in a specific cell type or at a specific developmental stage is dependent on:

 

regulated activation of transcription

The term “gene expression” refers to

 

initiation of transcription of a subset of target genes.

Loss-of-function mutations ________________________.

 

are usually recessive.

During gel electrophoresis, DNA fragments _______________________.

 

travel through a matrix containing a microscopic network of pores.

Which of the following techniques is not appropriate if you want to examine the transcriptome of a specific tissue?

 

in situ hybridization

Which of the following can limit the use of RNA interference in studying gene expression and function?

 

RNAi does not efficiently inactivate all genes.

 

Certain tissues are resistant to the action of RNAi.

 

Off-target effects are common in RNAi treatments.

The complete set of information in an organism’s DNA is called its

genome

You discover that the underlying cause of a disease is a protein that is now less stable than the non-disease-causing version of the protein. This change is most likely due to

 

a mutation within a gene.

Which of the following statements is FALSE?

 

Mutations in somatic cells are passed on to individuals of the next generation.

Mutations in protein-coding genes can affect the protein product in a variety of ways. Which of the following is most likely to result in a loss of protein FUNCTION? (Two answers are correct; select both.)

 

A point mutation in the gene coding DNA which, when translated, results in a premature stop codon.

 

A point mutation in the DNA coding for a protein activation domain.

Your friend works in a lab that is studying why a particular mutant strain of Drosophila grows an eye on its wing. Your friend discovers that this mutant strain of Drosophila is expressing a transcription factor incorrectly. In the mutant Drosophila, this transcription factor, which is normally expressed in the primordial eye tissue, is now misexpressed in the primordial wing tissue, thus turning on transcription of the set of genes required to produce an eye in the wing primordial tissue. Which of the following types of genetic change would most likely lead to this situation?

 

a mutation within an upstream enhancer of the transcription factor gene

What is the difference between a forward genetic screen and a reverse genetic screen?

 

In forward genetic screens, researchers induce mutations randomly across the genome.

The distinct characteristics of different cell types in a multicellular organism result mainly from the differential regulation of the _________________.

 

transcription of genes transcribed by RNA polymerase II.

_______ are proteins that bind DNA and facilitate the tight “twisting” of DNA around histones, thereby permitting activation or repression of transcription of specific genes.

 

Chromatin remodeling factors

What is an “enhancer”?

 

a place in the DNA where transcription factors bind

 

an open/relaxed region of chromatin

 

a small region of DNA

RNA in cells differs from DNA in that ___________________.

 

it is single-stranded and can fold up into a variety of structures.

Where in the cell (i.e., which organelle) does transcription of most messages take place?

 

nucleus

For a cell’s genetic material to be used, the information is first copied from the DNA into the nucleotide sequence of RNA in a process called _____ . RNA that is used as a template for protein production is called _____ .

 

transcription; mRNA

Transcription is a quite elegant way to direct protein production. Why?  

 

it allows DNA to be packaged tightly when not “in use” by the cell

 

saves energy: each cell has the same copy of the genetic information, but only uses what it “needs” at a specific time and place

 

it helps to protect the genetic material from errors

Which one of the following is the main reason that a typical eukaryotic gene is able to respond to a far greater variety of regulatory signals than a typical prokaryotic gene or operon?

 

The transcription of a eukaryotic gene can be influenced by proteins that bind far from the promoter.

How are most eukaryotic transcription regulators able to affect transcription when their binding sites are far from the promoter?

 

by looping out the intervening DNA between their binding site and the promoter

Combinatorial control of gene expression __________________________.

 

involves groups of transcriptional regulators working together to determine the expression of a gene.

.  What kinds of molecules act as extracellular signals?  

ions

 

lipids

 

proteins

In paracrine signaling, the signaling molecule

 

acts on cells in close proximity to the secreting cell.

The TGFβ superfamily of receptors are membrane-bound receptor tyrosine kinases. Dimerization of TGFβ receptors causes

 

activation of the signaling pathway via phosphorylation.

How are signals generated by a sending cell transported over long distances to a receiving cell?

 

via the bloodstream

What kinds of cell behaviors could be elicited by receiving an extracellular signal?

cell movement

 

cell death

 

cell proliferation

Which of the following statements is true?

 

The regulation of inflammatory responses at the site of an infection is an example of paracrine signaling.

Which of the following statements is true?

 

Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior.

Foreign substances like nicotine, morphine, and menthol exert their initial effects by _____.

 

interacting with cell-surface receptors, causing the receptors to transduce signal inappropriately in the absence of the normal stimulus.

The growth factor Superchick stimulates the proliferation of cultured chicken cells. The receptor that binds Superchick is a receptor tyrosine kinase (RTK), and many chicken tumor cell lines have mutations in the gene that encodes this receptor. Which of the following types of mutation would be expected to promote uncontrolled cell proliferation?

 

a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor

Which of the following mechanisms is not directly involved in inactivating an activated RTK?

 

dephosphorylation by serine/threonine phosphatases

When cells respond to an extracellular signal, they most often convert the information carried by this molecule from one form to another. What is this process called?

 

Signal transduction

Which statement about cell signaling is correct?

 

Each receptor is generally activated by only one type of signal molecule.

Under what condition will a target cell always respond quickly to an extracellular signal?

 

The response does not require changes in gene expression.

Which molecule performs the primary signal transduction step in cell signaling?

 

receptor protein

What is true of the GTP-binding proteins that act as molecular switches inside cells?

 

They are active when GTP is bound.

What are small intracellular signaling molecules often called?

 

second messengers

Which is true of signal integration?

 

It might involve a kinase in one signaling pathway inactivating a kinase in another pathway.

How can loss-of-function methods such as RNA interference or CRISPR, be used to assess the role of a protein in cell signaling?

 

They can be used to shut down genes encoding components of a signaling pathway.

What type of cell response would take the longest amount of time (on the scale of minutes to hours) to execute?

 

one that involves a change in gene expression

Enzymes that add a phosphate group to a switch protein are called

 

kinases

The creation of cells from pre-existing cells via a regulated cycle of events is known as 

 

proliferation

BrdU and EdU are frequently used as assays to measure the number of actively proliferating cells. Why does the incorporation of these synthetic nucleotides into cellular DNA reflect active cell proliferation?

 

BrdU and EdU are analogs of thymidine, and are added to the new DNA strand at replication.

Which of the following is the correct series of events leading to the creation of a new cell?

 

G1 ->S ->G2 ->M ->cytokinesis

Commitment of a cell to a new cell division (referred to as “START”) occurs in

G1

Cyclins

 

propel the cell cycle forward by regulating the stage in which they are expressed, and set in motion the preparation events necessary for the next stage.

 

are present only during the cell cycle stage that they trigger.

 

bind and activate cyclin-dependent kinases.

Progression through the cell cycle requires a cyclin to bind to a Cdk because _________.

 

the binding of a cyclin to Cdk is required for Cdk enzymatic activity.

What would be the most obvious outcome of repeated cell cycles consisting of S phase and M phase only?

 

The cells produced would get smaller and smaller.

Which of the following events does not usually occur during interphase?

 

The nuclear envelope breaks down.

In which phase of the cell cycle do cells check to determine whether the DNA is fully and correctly replicated?

 

at the end of G2

Which of the following statements about the cell cycle is false?

 

Once a cell decides to enter the cell cycle, the time from start to finish is the same in all eukaryotic cells.

Which of the following descriptions is consistent with the behavior of a cell that lacks a protein required for a checkpoint mechanism that operates in G₂?

 

The cell would enter M phase under conditions when normal cells would not.

Cell cycle events monitored by checkpoint pathways include

spindle position.

 

cell growth.

 

DNA damage.

Mitogens are _____.

 

extracellular signals that stimulate cell division.

Of the following mutations, which are likely to cause cell-cycle arrest?

Of the following mutations, which are likely to cause cell-cycle arrest?

Programmed cell death occurs ________________.

 

by means of an intracellular suicide program.

The notochord is a ___ structure in vertebrate embryos that lies under the ___, and is flanked by ___.

 

mesodermal, neural tube, somites

Hox genes:

 

encode transcription factors which specify a position along the anterior-posterior axis

In mouse, the formation of the neural tube relies on what cell biological processes?

 

Both changes in cell shape in the neural plate and changes in adhesion molecule expression in the neural tube are required during formation of the neural tube.

Which of the following are NOT derivatives of the neural crest cells?

 

pancreatic beta cells

Which of the following birth defects arises from a failure to close the neural tube?

 

microcephaly

 

spina bifida

 

cleft palate

What aspects of neural tube formation are regulated by Shh?

 

establishing ventral neuronal cell fates

Shh signaling from the notochord forms a protein gradient in the neural tube. Which other signaling ligand opposes Shh signaling activity?

 

BMP signaling

Which event in neural tube formation must come first?

 

folding at the medial hinge point

From which cell layer do the neural crest cells arise?

 

ectoderm

Neural crest cells can be roughly divided in four sub-groups, based on

 

anatomical region that they migrate into

Neural crest cells are specified distinct from the neural plate and epidermis by

 

receiving Wnt signals first, followed by BMP signals

Prior to migration, neural crest cells undergo an ________ transition, in which they change down-regulate E-cadherin, extend lamellipodia, and _______ from the neural tube.

 

epithelial-mesenchymal; migrate

Pharyngeal arches are

 

regions of the head and neck into which neural crest cells migrate

Neural crest cells and migrating axons are similar in that they

 

both utilize chemoattractants in the environment to move in the right direction

 

both use RhoGTPases to regulate the growth of filopodia

 

both extend microtubule-filled filapodial “feelers” into the environment to pull the cell forward

From which cell layer do the neural crest cells arise?

ectoderm

Neural crest cells can be roughly divided in four sub-groups, based on

 

anatomical region that they migrate into

Neural crest cells are specified distinct from the neural plate and epidermis by

 

receiving Wnt signals first, followed by BMP signals

Prior to migration, neural crest cells undergo an ________ transition, in which they change down-regulate E-cadherin, extend lamellipodia, and _______ from the neural tube.

 

epithelial-mesenchymal; migrate

Pharyngeal arches are

 

regions of the head and neck into which neural crest cells migrate

Neural crest cells and migrating axons are similar in that they

both utilize chemoattractants in the environment to move in the right direction

 

both extend microtubule-filled filapodial “feelers” into the environment to pull the cell forward

 

both use RhoGTPases to regulate the growth of filopodia

Which of the following statements about the cytoskeleton is FALSE?

 

Covalent bonds between protein monomers hold together cytoskeletal filaments.