Exam 3 Quizzes

Much of the human genome does not code for proteins. Which of the following types of DNA are found in these regions of the genome? a. DNA that is transcribed into several kinds of small RNAs with biological function b. DNA that consists only of histone coding sequences c. DNA that serves as binding sites for reverse transcriptase d. DNA that is translated directly without being transcribed

a. DNA that is transcribed into several kinds of small RNAs with biological function

Which statement is true about innate immunity? a. Innate immunity is the first, and most general, mechanism of protection against pathogens b. The extent of an innate immunity response depends on an infected animal's previous exposure to a pathogen c. Innate immunity is based on recognition of antigens that are specific to a pathogen d. Only vertebrates use innate immunity

a. Innate immunity is the first, and most general, mechanism of protection against pathogens

A researcher uses the chemical inhibitor cyanide to reduce ATP production in a neuron. What would be one effect of preventing ATP production? a. The "resting" distribution of potassium and sodium ions would be altered. b. The sodium and potassium channels would all be closed. c. The membrane would become more permeable to sodium. d. The physical structure of the plasma membrane would break down.

a. The "resting" distribution of potassium and sodium ions would be altered.

Which of the following statements about endocrine glands is true? a. They do not have ducts. b. The products are all enzymes. c. They secrete a product onto a body surface or into a body cavity. d. They secrete enzymes and bicarbonate.

a. They do not have ducts.

In which of the following locations would we expect to find the release of neurotransmitter molecules? a. in a chemical synapse b. in the cell body of a neuron c. along the length of a dendrite d. inside of an axon hillock

a. in a chemical synapse

When taken up by a cell, which of the following molecules binds to a repressor so that the repressor no longer binds to an operator? a. inducer b. corepressor c. cAMP d. promoter

a. inducer

Within a differentiated B cell, the activity of which molecule results in the rearrangement of DNA sequences between variable regions and joining regions? a. recombinase b. RNA polymerase c. reverse transcriptase d. telomerase

a. recombinase

Which of the following molecules is a protein produced by a regulatory gene? a. repressor b. promoter c. operator d. operon

a. repressor

Testosterone is an example of a chemical signal that affects, variously, the very cells that synthesize it in the testis, the neighboring cells, and distant cells outside the gonads. Thus, testosterone is an example of ________. a. an autocrine signal, a paracrine signal, and an endocrine signal b. a paracrine signal, a synaptic signal, and an exocrine product c. an autocrine signal, a neuroendocrine signal, and a synaptic signal d. a neurohormone signal, a neuroendocrine signal, and an exocrine product

a. an autocrine signal, a paracrine signal, and an endocrine signal

Tadpoles undergo metamorphosis in their development. The changes include reabsorption of the tail, growth of limbs, and the development of lungs. Amazingly, all of these changes are induced by thyroxine. Which of the following best explains the diverse effects of thyroxine? a. Different tissues have thyroxine receptors that activate different signal transduction pathways. b. Thyroid hormone is divided into T3 and T4 as it travels through the bloodstream. c. Thyroxine binds to transport proteins that direct thyroxine to certain tissues. d. Some tissues have membrane receptors for thyroxine, while other tissues have thyroxine receptors within the nucleus.

a. Different tissues have thyroxine receptors that activate different signal transduction pathways.

Which of the following correctly describes a strategy that bacteria have evolved to defend against infection by phage? a. The CRISPR-Cas system allows bacteria to recognize phage strains that have previously infected that bacterial lineage and targets the phage DNA for destruction. b. The lysogenic cycle allows bacteria evolve inhibitors that bind with the phage DNA they contain so their daughter cells will no longer be infected. c. Bacteria secrete enzymes that diffuse away from the cell and digest phage capsid proteins so the virus cannot infect the cells. d. Bacteria methylate phage DNA as it enters the cell, targeting it for destruction by restriction enzymes.

a. The CRISPR-Cas system allows bacteria to recognize phage strains that have previously infected that bacterial lineage and targets the phage DNA for destruction.

If a researcher moves the operator to the far end of the operon, which of the following processes would likely occur when the cell is exposed to lactose? a. The genes of the lac operon will be transcribed continuously. b. The inducer will no longer bind to the repressor. c. The operon will never be transcribed. d. The repressor will no longer bind to the operator.

a. the genes of the lac operon will be transcribed continuously

An increasing portion of female elephants in Mozambique are born without tusks which seems to allow them to survive better, as they are not the target of poachers. A recent study found out why male elephants are never tuskless. It's because _____ a. only males need their tusks for feeding. b. a male with the tuskless variant will die in his mother's womb. c. males need their tusks for fighting. d. only males need their tusks to dig water holes.

b. a male with the tuskless variant will die in his mother's womb.

Which statement best describes the concept of clonal selection? a. V, J, and C gene segments are rearranged b. an antigen can provoke production of high amounts of specific antibodies c. HIV (human immunodeficiency virus) can disrupt the immune system d. macrophages can recognize specific T cells and B cells

b. an antigen can provoke production of high amounts of specific antibodies

A bacterium has the following characteristics: · It adheres to the human intestinal lining using a feature that protects it from phagocytes, bacteriophages, and dehydration. · It can survive being boiled. · It contains no plasmids and relatively little peptidoglycan. Which of the following characteristics allows this bacterium to survive in a human who is taking penicillin pills? a. lipopolysaccharides in the cytoplasm b. gram-negative cell wall c. long polypeptides in the cell wall d. peptidoglycan in the cell wall

b. gram-negative cell wall

Which of the following best explains why the steroid hormone aldosterone affects only a small number of target cells in the body? a. nontarget cells destroy aldosterone before it can bind b. only target cells contain aldosterone receptors c. only target cells are exposed to aldosterone d. aldosterone is unable to diffuse through nontarget cell membranes

b. only target cells contain aldosterone receptors

Which of the following mechanisms is commonly used to coordinate the expression of multiple, related genes in eukaryotic cells? a. Related genes are organized in operons that share a promoter that controls their expression. b. Groups of genes that are expressed together have specific combinations of control elements. c. Environmental signals entering the cell cause the genes to rearrange into related sets. d. Release of each gene's individual inducing molecule must be coordinated to coordinate gene expression.

b. Groups of genes that are expressed together have specific combinations of control elements.

Which of the following are properties of steroid hormones? a. Steroid hormones are water-soluble and travel freely in the bloodstream. b. Steroid hormones regulate gene transcription by binding to intracellular receptor proteins. c. Steroid hormones usually exert their effects on target cells through membrane receptor proteins. d. Steroid hormones only act locally, on cells close to where the steroid hormone was secreted.

b. Steroid hormones regulate gene transcription by binding to intracellular receptor proteins.

Which of the following conditions is most likely to result in transcription of the lac operon? a. The cAMP level is high and the lactose level is low. b. The cAMP and lactose levels are both high within the cell. c. There is glucose but no lactose in the cell. d. There is more glucose in the cell than lactose.

b. The cAMP and lactose levels are both high within the cell

How does breakdown of glucose inhibit transcription of the lac operon? a. by weakening the binding of the repressor to the operator b. by reducing the levels of intracellular cAMP c. by strengthening the binding of the repressor to the operator d. by inhibiting RNA polymerase from opening the strands of DNA to initiate transcription

b. By reducing the levels of intracellular cAMP

Which of the following events or characteristics is the most likely explanation for why an individual experiences regular herpesvirus-mediated cold sore or genital sore flare-ups? a. They have been reinfection by exposure to the same herpesvirus strain. b. Copies of the herpesvirus genome permanently maintained in host nuclei (provirus) are periodically "activated." c. They have been reinfection by exposure to a different, but closely related herpesvirus strain. d. Copies of herpesvirus particles that have escaped the immune system periodically experience conditions that allow them to replicate and infect cells.

b. Copies of the herpesvirus genome permanently maintained in host nuclei (provirus) are periodically "activated."

`Which of the following is a molecule that helps to "turn off" the expression of genes in a cell? a. operator b. corepressor c. promoter d. inducer

b. corepressor

Which of the following are similarities between B cells and T cells? I) Both recognize antigens using immunoglobulin receptors. II) Both undergo clonal selection after encountering an antigen. III) Both maintain an immunological memory of previously encountered antigens. a. only II b. only III c. II and III d. I and II

c. II and III

Which of the following results is most likely to occur if acetylation of histone tails in the chromatin of embryonic cells is increased? a. increased chromatin condensation b. decreased binding of transcription factors c. decreased chromatin condensation d. inactivation of the selected genes

c. decreased chromatin condensation

Which of the following statements correctly describes exotoxins and endotoxins produced by various bacteria? a. exotoxins are components of the outer membrane of the bacteria that produce them b. exotoxins are only released into the environment when the bacteria dies and their cell walls break down c. exotoxins are secreted into the environment while the bacteria is still alive d. endotoxins are secreted into the environment while the bacteria is still alive

c. exotoxins are secreted into the environment while the bacteria is still alive

Which of the following are typical features of an inflammatory response? a. release of substances to decrease the blood supply to an inflamed area b. inhibiting the release of white blood cells from bone marrow c. increased activity of phagocytes in an inflamed area d. reduced permeability of blood vessels to conserve plasma

c. increased activity of phagocytes in an inflamed area

Which of the following pairs have antagonistic effects towards each other? a. the central nervous system and the peripheral nervous system b. the motor system and the autonomic nervous system c. the sympathetic and parasympathetic divisions of the autonomic nervous system d. the enteric nervous system and the motor system

c. the sympathetic and parasympathetic divisions of the autonomic nervous system

Which of the following statements correctly describes the primary difference between enhancers and proximal control elements? a. Enhancers improve transcription; proximal control elements inhibit transcription. b. Enhancers are long regions of DNA; proximal control elements are shorter RNA molecules that stand in for DNA. c. Enhancers are located considerable distances from the promoter; proximal control elements are close to the promoter. d. Enhancers are transcription factors; proximal control elements are DNA sequences.

c. Enhancers are located considerable distances from the promoter; proximal control elements are close to the promoter.

Which of the following molecules binds with a repressor to alter its conformation and therefore affect its function? a. promoter b. transcription factor c. inducer d. cAMP

c. inducer

Which critical role do transposons (i.e., ancient virus DNA ) play on the host genome, as suggested by a recent study? a. Increase the health of host cells b. Increase cell division in host cells c. Decrease the life span of host cells d. Help with gene regulation in the host cell

d. Help with gene regulation in the host cell

Vertebrate immune cells, which are phagocytic, include which of the following? I) neutrophils II) macrophages III) dendritic cells IV) natural killer cells a. I and IV only b. II and IV only c. I and III only d. I, II, and III

d. I, II, and III

Which of the following responses explain why the apparent high rate of mutation in RNA viruses? a. RNA viruses can incorporate a variety of nonstandard bases. b. RNA viruses are more sensitive to mutagens. c. RNA nucleotides are more unstable than DNA nucleotides. d. RNA virus genome replication does not involve proofreading.

d. RNA virus genome replication does not involve proofreading.

Which of the following characteristics is typical of the lytic cycle of a bacteriophage? a. The viral genome replicates without destroying the host. b. The host sequesters viral particles in the lysosome. c. Viral DNA incorporates into the host genome. d. The host membrane ruptures, releasing many phages.

d. The host membrane ruptures, releasing many phages.

You and your friend were equally exposed to a virus, but over the next few days, only your friend acquired flu-like symptoms and was ill for almost a week before recovering. Which one of the following is a logical explanation for this? a. Your friend had allergies. b. Your inflammatory response worked more quickly than your friend's response. c. Your friend had an autoimmune disorder. d. You had an immunological memory of that virus.

d. You had an immunological memory of that virus.

Excitatory postsynaptic potentials (EPSPs) occurring at multiple synapses on the same postsynaptic neuron can add together through ________. a. highly branched dendrites b. the generation of substance P c. temporal summation d. spatial summation

d. spatial summation

If a mutation deactivated a regulatory gene of a repressible operon in an E. coli cell which of the following describes the most likely outcome? a. irreversible binding of the repressor to the operator b. complete inhibition of transcription of the structural gene controlled by that regulator c. continuous translation of the mRNA because of alteration of its structure d. continuous transcription of the structural gene controlled by that regulator

d. continuous transcription of the structural gene controlled by that regulator

Which of the following statements correctly describes F- cells and F+ cells? a. F+ cells function as DNA recipients during conjugation and F- cells function as DNA donors during conjugation b. Both types of cells can donate F plasmids to other cells c. Neither types of cells can donate F plasmids to other cells d. F+ cells function as DNA donors during conjugation and F- cells function as DNA recipients during conjugation

d. F+ cells function as DNA donors during conjugation and F- cells function as DNA recipients during conjugation