Bio 1703 FINAL EXAM

A major research study is published in a peer-reviewed journal that demonstrates an increased incidence of cancer in people who live in cities close to overhead electrical wires, compared to people who live farther away from these power lines. The results are statistically significant and are widely disseminated in articles by respected media outlets. The news spreads fear around the world that very low-level electromagnetic fields, to which we are all commonly exposed, are dangerous for human health. Which of the following statements would be a valid conclusion based on the science?

The findings of increased cancer rates will not be sufficient to prompt cities to move electric power lines until independent scientists can conduct studies that eliminate other possible reasons for the increased cancer incidence found in this one study.

To differentiate between misinformation and legitimate science you should ask three questions: Is the

provider of information credible? Does the provider of the information have the expertise to vouch for the

claim? And....

s there a consensus among relevant scientific experts?

After 12 years of painstaking work, researchers managed to grow an Asgard archaeon species in a

2 laboratory bioreactor. Which of the following characteristics of this organism is most relevant to our understanding of the evolution of Eukaryotes?

cellular protrusions extending from the cell body, intertwined with two other prokaryotic species

Which of the following elements is NOT a component of the cytoskeleton?

nucleosomes

You've been having trouble focusing and your doctor writes you a prescription for a new medication. When you get home from the pharmacy, you notice that the drug comes with an insert that includes a long list of potential side effects. Worrying that this treatment might be worse than your initial problem, you do extensive web searches to decide whether to take the new pills. Which of the following sources will provide the information you can most rely on?

A published study conducted by outside researchers that compares the outcomes for 1000 people with attention deficit disorder, half of whom were randomly selected to take the drug and half of whom were unknowingly given a placebo instead

The most important factor that should convince you to conclude that a scientific research article is trustworthy is:

The researchers have a reputation as experts in the field of work that is being reported.

All natural sources of drinking water contain low levels of contaminants from geological sources. For example, arsenic is often present in parts per million. The presence of arsenic in drinking water has been tested repeatedly in mice and found to have no effect on their health even at much higher levels than those that occur naturally. However, studies of people who have been drinking water containing different trace levels of arsenic all their lives reveal an increased level of bladder cancer that begins to appear after 30 years. The more arsenic in drinking water the more cancers, with no amount that can be judged to be "completely safe".

A cost-benefit analysis should be conducted to determine some level of arsenic in drinking water that a society will need to tolerate, recognizing that we cannot afford to eliminate every death from bladder cancer caused by arsenic in drinking water.

Twenty physicians who care for people with autoimmune disease X are given approval to test whether drug Z—a medication that has previously been authorized as safe and effective for treating a different disease—can help their patients, too. Each of these doctors treats half of their patients with the drug and the other half with a placebo. Most are disappointed to find no significant difference in symptoms between the two groups. However, Doctor Jones finds that considerably more of his drug-treated patients improve than do his patients treated with a placebo; in fact, a statistical analysis shows that his result would be obtained by chance only one in twenty times. Excited by this result, Doctor Jones quickly publishes his results in a peer-reviewed journal; the 19 studies that found no effect are never published.

As a result of Doctor Jones's findings, many thousands of patients with disease X are subsequently trea

Taking patients off the placebo, so that twice as many could be treated with drug Z.

You are part of an exobiology (the branch of science that deals with the possibility and potential nature of life on other planets) team studying potential life-forms on an asteroid. Your team is testing the hypothesis that alien life-forms would also be composed of cells, just like terrestrial (Earth-based) life-forms. You have identified several structures that you think might be cells of alien life-forms. Which of the following criteria would be MOST useful in determining whether or not these structures could be cells?

The presence of catalytic molecules arranged in an organized structure (Do they have molecules that function as enzymes? Are these arranged in the cell in an organized fashion?)

Antibiotics tend to target features that are unique to bacterial cells and absent from eukaryotic cells such as our own. Which of the following would present a safe target for a new antibiotic?

cell wall

You are studying a recently discovered protozoan and have found what appears be a new organelle of unknown function. You hypothesize that it may have resulted from a new endosymbiotic event. Which of the following properties of the organelle would support this hypothesis? Choose all that apply—there may be more than one correct answer.

The new organelle is surrounded by two independent membranes.

AND

The new organelle contains DNA.

The cytoskeleton is responsible for:

Directed cell movements

A scientist wants to examine a small structure on the surface of a bacterial cell, close to the base of the flagellum. Which microscope will be MOST useful?

Scanning electron microscope

Antibiotics tend t o target features that are unique to bacterial cells and absent from eukaryotic cells such

as our own. Which of the following would present a safe target for a new antibiotic?

Peptidoglycan

hich of the following is considered key evidence in support of the endosymbiosis theory of

organogenesis?

Mitochondria have both inner and outer membranes

AND

Ribosomal RNA of mitochondria is similar to bacterial RNA

AND

Ribosomal RNA of chloroplasts is similar to bacterial RNA

A scientist wants to examine a structure inside of a eukaryotic cell that is hypothesized to influence the

organization o f DNA strands, but i s unable t o b e fluorescently labeled. Which microscope will b e MOST

useful?

Transmission electron microscope

Which organelle is the "mystery organelle" in the diagram below? What kind of cell is it?

Nucleus; eukaryote

Which bacteria are photosynthetic?

Cyanobacteria/blue-green algae

As you look at a series of cells under a light microscope, you notice that they are connected with cell walls

and contain chloroplasts and large vacuoles. Because you have studied diligently i n your cellular and

molecular biology class you are able to determine you are looking at:

Plant cells

An ionic bond between two atoms is formed as a result of the:

Transfer from one atom to the other

The complex macromolecules (e.g. polysaccharides) of the cell are built from simpler molecular monomer

subunits (e.g. amino acids, nucleotides) that are linked together through what type of chemical reaction?

Condensation

Which of the following monomer building blocks is necessary to assemble phospholipids around and

inside cells?

Fatty acids

What type of bond is indicated by the arrow in the diagram below?

Phosphodiester

Which bond/interaction is weakest on its own but strong through an additive effect of many interactions?

Van der Waals

Which is necessary for hydrolysis to occur?

H2O

Which monomer is used to construct proteins?

Amino Acids

A nucleoside is different from a nucleotide in that a nucleoside has

No Phosphate group

Glucose and ribose are both...

Sugars

NADH is used for..... while NADPH is used for....

Catabolic processes; anabolic processes

When there is an excess of nutrients available in the human body, insulin is released to stimulate the

synthesis of glycogen from glucose. This is a specific example of a/an ......... process, a general process

in which larger molecules are made from smaller molecules.

anabolic steroids

What interaction is stabilized by the greatest quantity of noncovalent interactions? Consider the quantity of noncovalent interactions in terms of the stability of the interaction.

The surfaces of A and D match well and therefore can form enough weak bonds to withstand thermal jolting; they therefore stay bound to each other during the experiment.

The melting point of an ionic solid is the temperature at which the crystal separates into its constituent ions. For sodium chloride, the melting point in air is 801°C. However, when sodium chloride is added to water at 37°C (human body temperature), the sodium and chloride ions separate readily. How can we explain this apparent paradox?

The highly polar water molecules are able to interact with the charged sodium and chloride ions, shielding the charges from each other and allowing them to separate at a much lower temperature, whereas the nonpolar molecules of air do not readily interact with the ions.

Oxidation is the process by which oxygen atoms are added to a target molecule. Generally, the atom that is oxidized will experience which of the following with respect to the electrons in its outer shell?

a net loss

Although individual reactions in the cell may be energetically unfavorable and not spontaneous, they can be driven forward if they are linked to another highly favorable chemical reaction. Given the reaction A → B where the ΔG° = +15 kJ/mol, which of the following reactions would be considered a sequential reaction that is spontaneous? Choose more than one response.

B → C with a ΔG° = −17.5 kJ/mol

AND

B → D with a ΔG° = −17.5 kJ/mol

Enzymes facilitate chemical reactions by:

lowering the activation energy of the reaction

The 2nd law of thermodynamics dictates that disorder in a system is always....

increasing

AG° indicates the change in the standard free energy a s a reactant i s converted t o product. Given what you

know about these values, which reaction below is the most favorable?

glucose→CO≥+H≥O AG°= -686 kcal/mole

What is the role of ATP in the cell?

Activated carrier molecule

AND

Stores energy in phosphoanydride bonds

AND

Drives unfavorable reactions by creating phosphorylated high-onergy intermediates

Oxidation is ....... while reduction is........

Loss of electrons; gain of electrons

.......store and transfer energy in a form that cells can use

Activated Carriers

........and........ are complementary processes that result in organisms obtaining useful chemical-bond energy they need to survive

Photosynthesis; cellular respiration

Motor proteins use the energy in ATP to transport organelles, rearrange elements of the cytoskeleton during cell migration, and move chromosomes during cell division. Which of the following mechanisms is sufficient to ensure the unidirectional movement of a motor protein along its substrate?

A conformational change is coupled to ATP hydrolysis

Two or three α helices can sometimes wrap around each other to form coiled-coils. The stable wrapping of one helix around another is typically driven by __________ interactions.

hydrophobic

Which of the following best describes the stable protein-ligand interaction that is represented in the image? Be sure to use the image as a guide but apply your knowledge regarding how protein and ligand commonly interact with each other. A note of caution though: the red lines in the figure are merely representing interactions and are not meant to be quantified.

The formation of a set of many weak, noncovalent interactions maintains the interaction between protein and ligand.

Molecular chaperones can work by creating an "isolation chamber." What is the purpose of this chamber?

This chamber serves to protect unfolded proteins from interacting with other proteins in the cytosol, until protein folding is completed.

Which statement concerning feedback inhibition is false?

Feedback inhibition is difficult to reverse.

In the 1920s, bacteriologist Fred Griffith demonstrated that a heat-killed, infectious pneumococcus produced a substance that could convert a harmless form of the bacterium into a lethal one. Fifteen years later, researchers prepared an extract from the disease-causing S strain of pneumococci and showed that this material could transform the harmless R-strain pneumococci cells into the infectious S-strain form. This change to the bacteria was both permanent and heritable, suggesting that this "transforming principle" represents the elusive genetic material of the cells. The researchers subjected their extract to a variety of tests to determine the chemical identity of the "transforming principle." In one experiment, they treated the material with enzymes that destroy all proteins. This treatment did not affect the ability of the extract to transform harmless bacteria into an infectious form.

The genetic material is not protein.

Which statement is true about the association of histone proteins and DNA?

Histone proteins have a high proportion of positively charged amino acids, which bind tightly to the negatively charged DNA backbone.

The human genome comprises 23 pairs of chromosomes found in nearly every cell in the body. How many telomeres are there in each cell?

92

What evidence suggests that the large amount of excess "junk" DNA in a genome may serve an important function?

A portion of "junk" DNA is highly conserved in its DNA sequence among many different eukaryotic species.

Which of the following is the true statement about the DNA double helix:

In a DNA double helix, the two DNA strands are complementary

Seed dormancy and seed germination are regulated in plants including Arabidopsis. Seed dormancy inhibits expression of seed germination genes and, under the right conditions, switching to germination inhibits seed dormancy gene expression. Plants also contain many reader and writer regulatory proteins that recognize and add methyl groups to lysines on histone H3 tails to maintain chromatin in daughter cells. The Arabidopsis protein SUVH4 is expressed during seed germination but not during seed dormancy. When expressed, SUVH4 adds methyl groups to the histone H3 tails on lysine 9 near genes involved in seed dormancy. Seed germination then occurs. The chromatin state near the seed dormancy genes is then inherited in daughter cells formed during seed germination.

Which of the following hypotheses fits with the above information?

The lysine 9 methylation leads to heterochromatin formation and reduced expression of genes involved in seed dormancy.

Catabolic pathways result in lost......., consistent with the 2 law of thermodynamics

Heat

Two or three a helices can sometimes wrap around each other t o form . The stable wrapping o f

one helix around another is typically driven by

Coiled-coils; hydrophobic interactions

.....generally carry extracellular signals from cell to cell

Signal Proteins

Which o f the following statements about allosteric regulators is FALSE?

Allosteric regulators block the active sites o f enzymes

Prions propagate by.

Inducing conversion i n normal proteins to an abnormal form through binding

The binding site where the reaction occurs on an enzyme i s called the:

Active Site

Which lab technique is used to visualize the structure of a protein using diffraction patterns?

X-ray crystallography

What should be the label for the item indicated by the question mark?

Ligand

What additional stabilizing bond is used by proteins, particularly in an extracellular environment?

Disulfide bonds

Fredrick Griffith's experiment provided important insights into biochemical basis of heredity when he

observed that a harmless strain o f Streptococcus pneumoniae could be transformed into a virulent strain

when it was combined with:

Heat killed virulent Streptococcus pneumoniae

How did Nettie Maria Stevens contribute to the field of genetics?

Discovered sex chromosomes in mealworms which would later be termed "X" and "y.»

Hershey and Chase used radiolabeled macromolecules in phage viruses to identify the material that

contained heritable information that was transferred to their bacterial hosts. What radioactive atom was

used t o track proteins during this experiment?

35S

Which scientist took the infamous "photograph 51" of DNA

Rosalind Franklin

The ......... uses ..........to condense and decondense chromatin as it positions

nucleosomes

Chromatin remodeling complex; ATP

Which of the following may be modified to mark regions of the genome for transcriptional activation or silencing

Tail of H3 Histone

Which animal displays the phenotype (physical characteristic) consistent with "mosaic" X-inactivation?

Tortoiseshell cats

Because hydrogen bonds hold the two strands o f a DNA molecule together, the strands can b e

separated without breaking any covalent bonds. Every unique DNA molecule "melts" at a different

temperature. In this context, Tm (melting temperature) is the point at which two strands separate, or

become denatured. Assuming the sequencing represent double-stranded DNA molecules, which

molecule will melt at the lowest temperature

TATTGTCT

Certain genes that were active in early development become subsequently repressed when development

is complete. Where would these genes be found in an interphase chromosome?

Heterochromatin

Eukaryotic cells use........to recognize specific chromatin modifications and

spread them to the nucleosomes nearby as part of an effective means of epigenetic inheritance.

Reader-writer complexes

Specific regions of eukaryotic chromosomes contain sequence elements that are absolutely required for

the proper transmission of genetic information from a mother cell to each daughter cell. Which of the

following is NOT known to be one of these required elements in eukaryotes?

Protein-coding regions

During DNA replication, as the replication bubble expands, this enzyme helps to remove kinks from the unwinding DNA.

Topoisomerase

What part of the DNA replication process would be most directly affected if ligase was missing from the replication process?

lagging-strand completion

Which of the following statements about sequence proofreading during DNA replication is false?

The exonuclease of DNA polymerase activity cleaves DNA in the 5′-to-3′ direction

Which of the choices below represents the correct way to repair the mismatch shown:

A

Sometimes, chemical damage to DNA can occur just before DNA replication begins, not giving the repair system enough time to correct the error before the DNA is duplicated. This gives rise to mutation. If the adenosine in the sequence TCAT is depurinated and not repaired, which of the following is the point mutation you would observe after this segment has undergone two rounds of DNA replication?

TCT

DNA replication follows which o f the following models:

Semiconservative

What part of the DNA replication process would b e most directly affected if primase was

missing from the replication process?

Okazaki fragment synthesis

With respect to the vertical line in the diagram of the replication bubble (below), in which

direction(s) does replication proceed?

Both

UV light produces......

Thymine dimers

During DNA replication, what does "A" represent in the figure? This is an enzyme that links

nucleotides to create a new DNA strand.

DNA polymerase

During DNA replication, what does "B" represent in the figure? This shows DNA polymerase

where to begin polymerization.

RNA primer

During DNA replication, what does "C" represent in the figure? This has gaps sealed by

ligase

Okazaki fragment

Telomeres play an important role in preventing the degradation of DNA. During DNA

replication, how is the telomere of the lagging strand completed?

Telomerase extends the end of the template strand using telomere repeats, at which point DNA polymerase can complete the lagging strand

Homologous recombination is an important mechanism in which organisms use a "backup" copy of the DNA as a template t o fix double-strand breaks without loss of genetic

information. Which of the following is NOT necessary for homologous recombination to occur?

5' DNA strand overhangs

Sometimes, chemical damage to DNA can occur just before DNA replication begins, not giving the repair system enough time to correct the error before the DNA is duplicated. This

gives rise to mutation. If the cytosine in the sequence CAT is deaminated and not repaired. Which of the following is the point mutation you would observe after this segment has

undergone two rounds of DNA replication?

TTAT

Which of the following provides additional protection on telomeres?

Shelterin complexes

Suppose that the A-T base pair indicated by the "*" above were deleted. What would the complete amino acid sequence of the protein produced by this gene be?

For this question, assume that the mRNA is transcribed immediately to the right of the last A-T base pair in the promoter sequence and ends immediately to the left o f the first G-C base pair in the terminator. This is a prokaryotic gene with no introns.

No protein produced

Unlike DNA, which typically forms a helical structure, different molecules of RNA can fold into a variety of three-dimensional shapes. This is largely because:

RNA is single-stranded

Which statement about mRNA splicing is TRUE:

Splicing must be precise because if extra nucleotides are left behind or excised from the transcript, the incorrect protein might be translated.

The sequence of the coding strand of a DNA molecule (that is, the DNA strand that contains the codons specifying the protein sequence) is 5'-CGGATGCTTA-3'. What is the sequence of the RNA made from this DNA?

5'-CGGAUGCUUA-3'

Investigators treat cells with a chemical that introduces random mutations into the DNA, including single-nucleotide changes that turn one base into another. They then isolate two mutants: one produces a protein that carries an alanine at a site that normally contains a valine; the other produces a protein that carries a methionine instead of the valine.

When these mutant cells are subjected to the same mutagenic treatment, they both produce proteins that contain a threonine at the site of the original valine. Assuming that the mutations causing these alterations are single-nucleotide changes, what were the codons that specified each of the amino acids discussed?

Val, GUG; Ala, GCG; Met, AUG; Thr, ACG

Which of the following is NOT a component of a ribosome?

M site

Transcription is the process by which:

Information in DNA is moved into mRNA

Translation is the process by which:

Information in mRNA is moved into amino acid sequences (proteins)

Transcription is initiated at a.......and ends at a........

promoter sequence; terminator sequence

Ribosomes build polypeptide chains using their active sites in what order?

A, P, E

.........add amino acids to the 3' end of ....... which deliver them to........

aminoacyl-tRNA synthetases; tRNAS; ribosomes

The splicing of exons is carried out by ...........

that, in part, form the........

nRNPs; spliceosome