Best of Ch. 11 HW

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

generation of multiple copies of a proto-oncogene that promotes cell division and inactivation of a tumor-suppressor gene (Excess copies of the proto-oncogene could stimulate cell division abnormally, and the inactivation of a tumor-suppressor gene would eliminate a brake on cell division.)

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

initiating mRNA synthesis (Transcription factors are proteins that regulate the transcription of DNA into mRNA.)

Which of these is NOT a carcinogen? -cigarette smoke -fat -testosterone -UV light -all of the above are carcinogens

-all of the above are carcinogens

1. A normal gene that, if mutated, can lead to cancer is called a(n) ......................... . 2. A gene that causes a cell to become cancerous is called a(n) ......................... . 3. A(n) ................................. is a gene that encodes proteins that inhibit cell division. Such proteins normally help prevent cells from becoming cancerous. 4. A(n) ....................... is a protein that promotes cell division. In excess, such a protein may lead to cancer.

1. proto-oncogene 2. oncogene 3. tumor-suppressor gene 4. growth factor

A DNA microarray is a glass slide with thousands of single-stranded DNA fragments fixed to it. Each fixed DNA fragment is from a particular gene. Therefore, a single microarray has DNA from thousands of genes. Biologists use DNA microarrays to figure out which genes are being transcribed by organisms in different situations.

1.) isolate mRNA from target cells2.) produce cDNA from mRNA3.) add cDNA to microarray wells4.) rinse to remove unbound cDNA5.) examine fluorescence on microarray

Which of these indicates an enhancer region?

A

_____ bind(s) to DNA enhancer regions.

Activators Activators are a type of transcription factor that bind to enhancer regions.

Which of these directly bind(s) to the promoter?

C and D Both RNA polymerase and transcription factors bind with the promoter.

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 often develop chronic conditions that are usually only associated with old age. (Dolly had to be euthanized at an early age due to severe arthritis and other health problems. Similar observations are made in cloned mice.)

Which of these is a regulatory gene?

D The regulatory gene is not a part of the operon.

The operon model of the regulation of gene expression in bacteria was proposed by _____.

Jacob and Monad (n 1961 Jacob and Monod proposed the operon model of gene regulation)

What is the function of a spliceosome?

RNA processing (Spliceosomes are involved in RNA processing)

What controls the way in which a zygote differentiates?

Selective genes are turned on and off, depending on the fate of the cell. (The particular genes that are active in each type of differentiated cell are the source of its particular function and structure.)

In fruit flies, there are molecules in the egg that determine the future head and tail ends of the animal. 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. (Injecting some "head" mRNA molecules into the tail end will cause the embryo to have an altered protein gradient in the tail end. As such, it will begin to make some of the head structures at the tail end.)

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. (Without the inhibition of Rb protein, the cells would have a much higher rate of cell division.)

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. (Adult stem cells are cells that produce a variety of different cells. Stem cells in bone marrow can produce many types of blood cells, for example)

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. (Some proteins are needed only for short-term use)

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 and therefore different proteins. (The same strand of mRNA can be spliced in different ways so that different polypeptides are coded for)

A mutation in the operator region of the trp operon can prevent the trp repressor from binding to this operator. When these mutant cells are placed in a solution containing chicken broth, which of the following events would happen?

Tryptophan would bind to the repressor. (Tryptophan would still bind to the repressor. However, the repressor would not be able to bind to the operator and switch off transcription. Thus, the cell would still be making tryptophan even though it is being supplied by the medium in which it is growing. This is a waste of energy for the cell.)

In eukaryotic cells, signal transduction pathways involve __________.

a series of relay molecules, of which the last activates a transcription factor (A signal molecule released by a nearby cell binds to the receptor on the surface of the cell. This then relays the signal to a transcription factor that enters the nucleus and interacts with the DNA.)

Can you correctly label the structures in this diagram that summarizes chromosome packing?

a- histone b- nucleosome c- supercoil d- chromosome e- chromatin

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 (This pattern suggests that a gene on the X chromosome is involved in the production of sweat glands. If a female is heterozygous for the disorder, she has one X chromosome that directs sweat-gland production and one that does not. Due to random chromosome inactivation, she will have patches both with and without sweat glands.)

Cloning experiments with differentiated root cells from carrots revealed that __________.

an entire plant can grow from a differentiated cell (A single cell from an adult plant gave rise to an entirely new plant.)

For the yeast Saccharomyces cerevisiae, cells of different mating types secrete factors that bind to specific receptor proteins on the cell surface of cells of the opposite mating type. This initiates a signal transduction pathway that eventually results in __________.

cell fusion (Cells of opposite mating types grow toward each other and fuse.)

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

complementary mRNA sequences (MicroRNA binds to complementary RNA sequences and either degrades that RNA or blocks its translation.)

_____ is a carcinogen that promotes colon cancer.

fat A diet high in fat increases the risk of both colon and breast cancer.

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 (If polyps are discovered during a colonoscopy, a doctor will monitor them carefully.)

In the presence of a regulatory protein the lac operon is _____.

not transcribed (The regulatory protein of the lac operon is a repressor.)

Enzyme complexes that break down protein are called _____.

proteasomes (Proteasomes are enzyme complexes that break down proteins.)

Protein-phosphorylating enzymes' role in the regulation of gene expression involves _____.

protein activation (Proteins are often activated by phosphorylation.)

The nuclear membrane's role in the regulation of gene expression involves _____.

regulating the transport of mRNA to the cytoplasm (This is the role of the nuclear membrane in the regulation of gene expression)

Which of these is NOT a component of the lac operon?

regulatory gene only (The regulatory gene, while not a part of the operon, plays a role in regulating the expression of the genes of the operon.)

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

spinal cord injuries (If given the right stimuli, stem cells could be differentiated into mature neurons that would replace the damaged ones.)

A mutation in the ras gene can __________.

stimulate cell division (The normal product of ras is a relay protein. A mutation can produce an oncogene that stimulates cell division. Ordinarily, a stimulatory pathway like this will not operate unless the growth factor is available. However, an oncogene protein that is a hyperactive version of a protein in the pathway may trigger the pathway even in the absence of a growth factor.)

After translation is complete, the insulin polypeptide is activated by __________.

the cutting of the initial translation product to yield two shorter chains joined together by sulfur linkages (This is the active form of the insulin protein.)

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 a comparison of which of the following?

the mechanisms of transcriptional control (Transcriptional control occurs in both prokaryotic and eukaryotic cells.)

Regulatory proteins bind to _____.

the operator (Transcription is inhibited when a regulatory protein binds to the lac operon operator.)

A fruit fly's head-to-tail axis is established by __________.

the position of mRNA in the egg cell (The location of egg cell mRNA at one end of the egg creates a regulatory protein gradient across the embryo that establishes a head-to-tail axis.)

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 (Transcription factors and activators are directly involved in regulating gene expression. They assist by binding to DNA sequences, which then allows RNA polymerase to bind to the promoter.)

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 (The nucleus of the intestinal cell retains all of the genetic information necessary to produce all of the different cells of a tadpole.)