BIOL350 final exam 2015 latest december

COURSE NAME: BIOL350 Cell and Molecular Biology

MULTIPLE CHOICE SECTION INSTRUCTIONS: Read all instructions carefully. Please answer all questions. Each question is worth 1 point. The Multiple Choice section is worth 20 points.

**Do not enter your answers here.** Type in the letter you select as the best answer on the Answer Sheet provided by your instructor.

1. The monomer unit of DNA is:

a. an amino acid

b. a nucleotide

c. a fatty acid

d. glucose

2. Disulfide bridges are a type of covalent bond critical to maintaining the 3dimensional shape of proteins. The amino acid involved in disulfide bridge formation is:

a. tyrosine

b. arginine

c. cysteine

d. glutamic acid

3. Sister chromatids form:

a. during G1

b. during G2

c. during S phase

d. during M phase

4. In a cell containing 10 chromosomes, mitosis results in the formation of daughter cells containing __________ chromosomes.

a. 5

b. 10

c. 20

d. 40

5. Mutant Ras proteins, which are found in many cancer cells, cannot hydrolyze their bound GTP to GDP, and therefore, a. cannot turn themselves on

b. cannot turn themselves off

c. cannot be degraded

6. Checkpoints during the cell cycle process allow cells to:

a. detect DNA damage

b. detect improper spindle formation during mitosis

c. check for unreplicated DNA following DNA synthesis (S phase) d. all of the above

7. When DNAs from two different organisms are incubated together, some duplexes are formed by DNA strands from the two species. What indicates that such duplexes are less stable than those between strands from the same organism?

(see page 519 of your text for a hint).

a. Heterogeneous duplexes melt at lower temperatures than homogeneous duplexes

b. Heterogeneous duplexes melt at higher temperatures than homogeneous duplexes

c. Heterogeneous duplexes are degraded faster

d. Heterogeneous duplexes are degraded more slowly

e. There is no difference in stability between homogeneous and heterogeneous duplexes

8. Why has the One Gene – One Polypeptide hypothesis had to be modified?

a. Genes can be spliced differently to generate a variety of related polypeptides

b. Enzymes sometimes consist of more than one polypeptide, each of which is coded for by its own gene

c. Enzymes actually code for genes

d. Polypeptides code for genes

9. The first amino acid incorporated into almost all proteins synthesized in eukaryotic cells is a(n) ____________.

a. methionine

b. arginine

c. valine

d. alanine

10. The tails of phospholipids are:

a. hydrophobic

b. hydrophilic

c. amphipathic

11. The organelle(s) in which carbohydrate modifications (glycosylation) of newly synthesized proteins are carried out:

a. nucleus

b. Golgi apparatus

c. lysosomes

d. rough endoplasmic reticulum

e. B and D

f. A and C

12. Multiple RNA transcripts can be generated from a single DNA template.

a. True

b. False

13. Signaling through G coupled proteins leads to a series of intracellular signals.

Choose the letter below that corresponds to the correct order of these signals.

a. activation of protein kinase A (PKA); formation of cyclic AMP (cAMP); activation of adenylyl cyclase

b. formation of cyclic AMP (cAMP); activation of adenylyl cyclase; activation of protein kinase A (PKA)

c. activation of adenylyl cyclase; formation of cyclic AMP (cAMP); activation of protein kinase A (PKA)

14. What is the function of the signal sequence located at the amino terminus of a protein

a. It directs the placement of the RNA on the protein portion of the ribosome.

b. It allows a protein to be directed to the nucleus, where it can function in transcriptional regulation.

c. It allows a protein to be directed and inserted into the endoplasmic reticulum so that it can be secreted by the cell.

15. Lipid bilayers are not permeable to:

a. ions

b. non-polar molecules

c. very small molecules such as CO₂

16. Which of the following is not an example of epigenetic inheritance?

a. the inheritance of methylation patterns in DNA

b. the inheritance of a single nucleotide mutation in the DNA

c. the inheritance of patterns of chromosome condensation

17. Which of the following is not a small intracellular signaling molecule (second messenger)?

a. cyclic AMP

b. phospholipase C

c. inositol triphosphate

d. diacylgylcerol

18. DNA replication results in:

a. Two DNA molecules, one with 2 old strands, one with 2 new strands

b. Two DNA molecules, each of which has 2 new strands

c. Two DNA molecules, each of which has 1 new strand and 1 old strand

19. Introns:

a. represent DNA sequences of a gene that are translated into protein

b. represent DNA sequences of a gene that are not translated into protein

c. are found more frequently in eukaryotes than bacteria

d. are found more frequently in bacteria than in eukaryotes

e. a and c

f. b and c

20. The correct order of mitosis is:

a. Metaphase, prophase, telophase, anaphase

b. Prophase, metaphase, anaphase, telophase

c. Anaphase, telophase, metaphase, prophase

************************************************************************************************************ MATCHING SECTION

MATCHING SECTION INSTRUCTIONS: Read all instructions carefully. Please answer all questions. Each question is worth 1 point. The Matching section is worth 12 points.

**Do not enter your answers here.** Type in the letter you select from the right column as the best answer on the Answer Sheet provided by your instructor.

**Do not enter your answers here.** Type in your best answer on the Answer Sheet provided by your instructor.

Complete each of the 5 questions in this Short Answer Section

INSTRUCTIONS: Each question is worth 4 points. Answers should be no more than 1 or 2 sentences. Total points for this section is 20 points.

**Do not enter your answers here.** Type your answers into the Answer Sheet provided by your instructor.

1. Why do calculations based on amino acid differences in proteins tend to underestimate the actual mutation rate?

2. Consider the DNA sequence shown below. If RNA polymerase transcribes the sequence from left to right, using the top strand as its template, what will the sequence of the RNA molecule produced be?

5’-ATGACGAAAAGA-3’

||||||||||||

3’-TACTGCTTTTCT-5’

3. Name two of the three types of cytoskeletal fibers and briefly define their function in the cell.

4. Most mRNAs coding for protein have long stretches of adenine ribonucleotides [poly(A)] on the 3' end of the message. Does that mean that each gene from which these mRNAs are derived has a corresponding stretch of poly(dT) at the 5' end of the template from which the mRNA was formed.

5. Describe two mechanisms used by the cell to convert a protein from an active to an inactive state.

Complete 6 out of 9 questions in this Essay Section

REQUIRED QUESTIONS: 1-4 must be answered.

ALTERNATE QUESTIONS: 5-9: Select 2 of these questions to answer.

INSTRUCTIONS: Each question is worth 8 points. Total points for this section is 48 points.

**Do not enter your answers here.** Type your answers into the Answer Sheet provided by your instructor.

REQUIRED QUESTIONS

1. The structure of biological membranes is determined primarily by the lipid bilayer but the specific functions of these membranes are carried out by proteins associated with the membrane. State whether you believe this statement is True or False and explain your answer.

2. Would you agree or disagree with the statement that differences in gene expression patterns can always be attributed to a difference in DNA sequence?

3. The mitotic Cdk cycle is depicted in the figure below. How does the mitotic Cdk-cyclin become active, i.e. what chemical reaction(s) must take place to convert the inactive mitotic Cdk-cyclin to the active mitotic Cdk-cyclin complex? What do you think would happen if the Anaphase-promoting complex were unable to function for some reason? Please explain your answers.

4. You have cloned the gene for a transcription factor. You notice that the protein encoded by the gene for the transcription factor can dimerize (2 copies of the protein come together to form a complex) and form a leucine zipper motif. The sequence adjacent to the leucine zipper motif is enriched in positively charged amino acids (see diagram below). Do you think the ability of your transcription factor to function as a transcription factor would be affected if you:

i. a). change the hydrophobic leucine motifs in the “zipper” to more polar amino acids. Why or why not?

ii. b. change the positively charged amino acids (shown in subunits 1 and 2) to non-charged amino acids. Why or why not?

ALTERNATE QUESTIONS **Choose 2 Questions to answer from the selection of questions below**

5. cAMP (cyclic AMP) is a secondary messenger (diffusible in the cytoplasm of the cell) involved in cell signaling processes. Describe in as much detail as possible how this secondary messenger is generated in response to cell signals and how it functions to modulate downstream events in cell signaling pathways-including changes in gene expression. Start your discussion by describing the class of cell surface receptor associated with increases in this second messenger and note in your response at least one step in signal transduction process where the signal initiated at the cell surface is amplified.

6. You have learned that the chemical nature of the side chains of amino acids (polar, nonpolar, charged) are important in determining overall protein structure. Given this, why do you think that addition of phosphate groups to proteins (as occurs during signal transduction) might affect protein structure/activity?

7. When cells are grown in the presence of radioactive thymidine it is incorporated into DNA during S phase. The results shown in the graph below come from an experiment in which cells are grown for 30 minutes in the presence of radioactive thymidine then the medium is replaced with medium containing non-radioactive thymidine (in other words, a pulse-chase procedure (for a brief description of pulse-chase experiments, see page 747 of your text)). The pulse chase approach allows investigators to track biomolecules labeled at the time of the pulse. At different times after replacement of the medium, the cells are examined by microscope to determine the number of cells undergoing mitosis (mitotic cells are easy to recognize as their chromosomes are obviously condensed). The fraction of mitotic cells that have incorporated the radioactive thymidine can also be determined and plotted as a function of time after thymidine labeling (see below).

a.At 10 hours –essentially 100% of the mitotic cells contain radioactive DNA-what phase of the cell cycle were these cells in when the radioactive thymidine was present? (4 points)

b.Why are there no mitotic cells that contain radioactive DNA at the initial time points? ( 4 points)

8. Although incorporation of the wrong nucleotide is not desirable in either the synthesis of DNA corresponding to a particular gene or in the mRNA transcribed off that DNA-explain why such a mistake is more deleterious at the DNA than RNA level.

9. A single mutation in the beta-globin chain of hemoglobin results in sickle cell anemia, a serious disease in which misshapen red blood cells can clog small blood vessels. The mutation results in the use of a valine rather than a glutamic acid as the seventh amino acid in the beta-globin protein. Do you think the results would be as devastating if the mutation resulted in aspartic acid being substituted for the glutamic acid? Why or why not?