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CellBio Chp11

Lac operon regulatory genes are _____.

continually expressed

A mistake during DNA replication prevents the trp repressor from binding to the operon operator. When these cells are placed in a solution containing chicken broth, what happens

Tryptophan would bind to the repressor.

What controls the way in which a zygote differentiates?

Selective genes are turned on and off, depending on the fate of the cell.

When are DNA molecules the least tightly coiled?

S phase of interphase

Anhidrotic ectodermal dysplasia is an X-linked disorder that results in the absence of sweat glands. How would this condition be manifested in a heterozygous female?

She would have a random pattern of tissue with and without sweat glands.

In eukaryotic cells, several proteins are involved in the process of transcription. This process involves enhancers that are _____

bound by activators causing DNA to bend

Alternative RNA splicing has revealed inaccuracies in the one gene-one polypeptide hypothesis. Why?

Transcription of the same gene can lead to the production of different mRNAs.

MicroRNA (miRNA) controls _____.

translation

Microtubules in the cytoplasm of the cell are composed of two protein subunits, α-tubulin and β-tubulin. Addition of colchicine to the cells results in the disassembly of the microtubules and consequently an increase in the concentration of tubulin subunits. Based on your knowledge of translational regulation, what changes in protein production would occur?

a decrease in the rate of production of tubulin

A similar protein is found in both a bacterial cell and a single-celled eukaryote. However, the prokaryote seems to produce a much higher amount of the protein. A detailed investigation of the control mechanisms of this protein in both organisms would include which of the following experiments?

the mechanisms of transcriptional control

In embryonic mice, a homeotic gene controls development of the neck, which includes the larynx and thymus. If this gene were deleted, a full-term mouse would show _____.

lack of development of the larynx and thymus

A researcher performs a DNA microarray but forgets to add the enzyme reverse transcriptase. This is important because the enzyme makes _____ from a(n) _____ template.

cDNA ... mRNA

In eukaryotic cells, signal transduction pathways involve _____.

a series of relay molecules, of which the last activates a transcription factor

Steward's experiment with carrot cells revealed that _____.

an entire plant can grow from a differentiated cell

Using nuclear transplantation, it is possible to generate _____ for therapeutic uses.

blastocysts

Since the first animal was produced using a fully differentiated cell, a number of observations have been made. Which of the following statements is true in regard to reproductive cloning?

Cloned animals develop chronic conditions that are usually only associated with old age.

Stem cells could be immensely important in the treatment of which of the following conditions?

spinal cord injuries

Proto-oncogenes have the potential to become oncogenes. Which of the following is most likely to lead to cancer?

a mutation that causes the proto-oncogene to become overactive

The Rb protein prevents mitosis by inhibiting cells from entering S phase. Human papillomavirus (HPV) is thought to inhibit the action of the Rb protein in cervical epithelial cells. What would be the effect of cervical cells being infected with HPV?

The mitotic rate would increase.

Colonoscopy is the examination of the large colon. It allows for visual diagnosis of ulcers and polyps, which may lead to colon cancer. A polyp _____.

is a cluster of abnormal cells

A mutation in the ras gene can _____.

stimulate cell division

Which of the following cell types would most likely have a high rate of error in DNA replication and consequently a rapid mutation rate?

epithelial skin cells

Which of the following molecules would bind to an operator?

an active repressor

In E. coli, the operon that controls lactose-utilization genes consists of _____.

three genes

In order to function as specialized cells, your muscle and bone cells undergo significant changes in gene regulation. This is because _____.

different genes are switched on and off in each type of cell

The female calico cat has a particular coat coloring because each cell contains _____ active X chromosome(s)

one

Testosterone enters human cells and binds to a specific protein inside the cell. This testosterone-protein complex is then transported into the nucleus where it binds to the cell's DNA. What is the function of the testosterone complex?

It helps RNA polymerase transcribe certain genes.

Hemoglobin is a molecule that is found in red blood cells. These molecules have to last for months because red blood cells have no nucleus and are unable to make more hemoglobin (they cannot transcribe from no template). However, most proteins are much shorter-lived. What is the advantage to this?

This enables cells to maintain a precise and efficient control over their activities.

In fruit flies, there are molecules in the egg that determine the body layout of the adult fly. What occurs when mRNA from the head end of an embryo is injected into the tail end of an early embryo?

Some head structures develop at the tail end; the head end develops normally.

Adrenaline is a "fight-or-flight" hormone and is released when danger threatens or in an emergency. It binds to a protein receptor, which causes a number of reactions to occur inside the cell. Enzymes are produced that perform a number of functions, including release of sugar into the bloodstream. What function does adrenaline play in this pathway?

signal molecule

Since the first animal was produced using a fully differentiated cell, a number of observations have been made. Which of the following statements is true in regard to reproductive cloning?

Cloned animals develop chronic conditions that are usually only associated with old age.

Stem cells could be immensely important in the treatment of which of the following conditions?

spinal cord injuries

A proto-oncogene is a normal gene that can change into an oncogene. Oncogenes are potentially lethal genes that can cause cancer. Why do cells continue to maintain these genes?

Proto-oncogenes are necessary for normal control of cell division.

Tobacco causes more cases and types of cancer than any other single agent. In individuals who inhale tobacco smoke, lung cancer is the most prevalent form of cancer. What form of cancer is second to lung cancer in estimated number of cases for this risk factor?

bladder

In prokaryotes, a group of genes with related functions is called _____.

an operon

Tryptophan is placed into a culture of E. coli cells. As a result, the bacterial cells switch off transcription of tryptophan because the amino acid binds to the _____.

repressor

The promoter of an operon _____.

is where RNA polymerase binds

In prokaryotes, operons _____.

regulate the rate of transcription

The gene for human growth factor is inserted into the E. coli lactose operon so that it replaces the structural genes with the gene for human growth factor. What substance must be added to the bacterial culture so that they produce human growth factor?

lactose

In E. coli the lactose operon (lac operon) is turned on in the presence of _____.

lactose

In some species of bacteria that are resistant to the antibiotic tetracycline, the antibiotic molecule attaches to a repressor protein. This prevents binding of the repressor to the bacterial DNA and allows a set of genes to be transcribed. The transcription of these genes is under the control of a(n) _____

operon

Some species of bacteria can either synthesize the amino acid glycine or absorb it from their surroundings. If glycine binds to a repressor protein, which then allows the repressor to bind to the bacterial chromosome, the operon will not be transcribed. If it is like other operons, the presence of glycine will result in the _____.

cessation of the synthesis of glycine

Operons _____.

function in frequently changing environments

In multicellular eukaryotic cells, the control of gene expression is more complex because _____

these cells have smaller chromosomes, so each gene must be multifunctional

Cells become specialized by a process known as _____

differentiation

Histones are _____.

proteins around which DNA is coiled

In eukaryotes, DNA packing seems to affect gene expression primarily by _____.

controlling access to DNA

In eukaryotes, chromosomes are tightly coiled due to the association of histone proteins and DNA. These structures are known as _____

nucleosomes

Nucleosomes _____.

wrap around the DNA for organization and compaction

Anhydrotic dysplasia is a genetic disorder in humans that results in the absence of sweat glands in the skin. Some men have this defect all over their bodies, but in women it is usually expressed in a peculiar way. Women with this disorder typically have small patches of skin with sweat glands and other patches without sweat glands. This pattern of sweat-gland distribution can be explained by _____

X chromosome inactivation

The DNA-histone complexes that are formed in eukaryotic cells directly inhibit _____.

Correct. The packing and unpacking of DNA provides a level of control for transcription. Activators cannot bind to enhancer regions until the DNA has unwound.

Enhancers are _____.

specific DNA sequences located distant to the promoter

Dioxin is a by-product of various industrial chemical processes. It is suspected of causing cancer and birth defects in both humans and other animals. Apparently, it acts by entering cells and binding to proteins, altering the pattern of gene expression. Therefore, it is reasonable to propose that dioxin acts by mimicking _____.

the role of transcription factors

Eukaryotes have the ability to switch gene expression on or off. If a repressor protein binds to a DNA sequence called a(n) _____, it may block gene expression.

silencer

In eukaryotes, gene expression is regulated mostly by _____.

controlling the transcription of genes

Which of the following is true of gene regulation in both eukaryotes and prokaryotes?

Transcription is the typical point at which gene expression is regulated.

MicroRNA (miRNA) functions by binding to _____ and blocking translation.

complementary mRNA sequences

Gene expression can also be controlled after the mRNA molecule has left the nucleus. These mechanisms may include the _____

breakdown of RNA

It is possible for a cell to make proteins that last for months—for example, hemoglobin in red blood cells. However, many proteins are short-lived and may be degraded in days or even hours. Why do cells make proteins with such a short life?

This enables cells to control the amount of protein present.

A scientist is investigating a new drug that blocks the action of the enzyme responsible for splicing mRNA molecules. If this drug is effective, which of the following statements will be true?

RNA would remain in the nucleus as it would be unable to move through the nuclear pores, thus blocking translation of the gene.

An animal's head-to-tail axis is established by _____

egg cell mRNA

DNA microarrays are useful tools for studying _____.

gene expression

A signal transduction pathway activates a transcription factor that responds by _____.

synthesizing mRNA

Some glucose transport molecules are controlled by levels of insulin. When insulin binds to a specific _____, the signal is relayed to a(n) _____ , which then controls gene expression.

receptor ... transcription factor

Clones are derived _____

from a single ancestor cell

Experiments involving _____ have demonstrated that differentiated cells contain all of the genetic information found in undifferentiated cells

nuclear transplantation

In frogs, when the nucleus of an intestinal cell of a tadpole is transferred to an egg whose nucleus has been removed (nuclear transplantation), some of the eggs will develop into normal tadpoles. This demonstrates that _____.

these cells have retained all of their genetic potential

Researchers successfully cloned Dolly the sheep, proving that cloning an adult animal cell can be successful. This type of cloning is known as _____

reproductive cloning

Why do you think that adult stem cells are found in bone marrow and the lining of the small intestine specifically?

These cells must be able to regenerate various types of cells throughout life.

Embryonic stem cells differ from adult stem cells because they _____

can differentiate into all cell types

Which of the following statements best describes cancer cells?

Normal controls over cell division have been altered.

Which of the following would be most likely to lead to cancer?

generation of multiple copies of a proto-oncogene and inactivation of a tumor-suppressor gene

In human cells, oncogenes _____.

stimulate cell division

Which of the following genes inhibit cell division?

tumor-suppressor genes

A cancer cell _____.

does not respond to the signals that control cell division

Most human cancers are _____.

caused by the accumulation of mutations

The p53 protein _____.

initiates transcription

In humans, most cancers are caused by _____.

tobacco

The leading cause of death in the United States is _____.

heart disease

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