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1

Ciprofloxacin (Cipro) is a broad spectrum antibiotic that is often used to treat infections for which the bacterial pathogen has not been identified, including urinary tract infections and abdominal infections.  The mechanism of action of this antibiotic in bacteria is as an inhibitor of which of the following enzymes?

 

A.  DNA Gyrase (Type II Topoisomerase)

B.  RNA polymerase

C.  Reverse Transcriptase

D.  Helicase

E.  DNA polymerase III

A. DNA Gyrase (Type II Topoisomerase)

2

A patient with Ewing sarcoma is given etoposide as part of his chemotherapy regimen. This drug interferes with topoisomerases. Topoisomerases are responsible for which of the following actions?

A. DNA polymerization     

B. Formation of DNA breaks during unwinding     

C. RNA primer synthesis

D. joining of the Okasaki fragments            

E. RNA primer degradation

B. Formation of DNA breaks during unwinding. 

3

4. A patient comes to clinic because her family has a history of multiple cancers at early ages, but they have tested negative for all the known familial cancer syndromes. A genetic marker, “ILB,” appears to be inherited with the unknown mutation in this family. The marker is present in six of her seven family members with the early cancers, but is absent in her maternal aunt, who has early-stage cancer. This finding in the maternal aunt likely results from:

A. Crossover during anaphase, causing the marker to be linked to the disease

B. Crossover during metaphase, causing the marker to be unlinked from the disease in this subject

C. Crossover over during metaphase, causing the marker to be linked to the disease in this subject

D. Crossover during prophase causing the marker to unlink from the disease in this subject

E. Crossover during prophase, causing the marker to be linked to the disease in this subject

D. Crossover during prophase causing the marker to unlink from the disease in this subject. 

4

Which is the second enzyme to function in prokaryotic DNA replication? 

Primase

5

What is the first enzyme that is active in prokaryotic DNA replication? 

Helicase

6

What is the third enzyme to function in prokaryotic DNA replication? 

DNA Polymerase III

7

A 12-year-old boy has learned that his mother’s husband may not actually be his biological father. He is determined to learn the truth, so he asks his mother for help. Unfortunately, the mother is not really sure, so they hire the services of a well-respected geneticist. This professional devises a test that he thinks will be specific. He knows of ways to cut chromosomal DNA at specific small palindromic sequences so that different alleles will give different patterns of cut fragments. He applies this technique to donated samples of DNA collected from all interested parties and soon finds one version of his test that yields a definitive result. .

     He has taken DNA samples from three men, as well as on the boy’s mother (M), her husband (H), and the boy himself (B) to perform his test, and the resulting fragments are separated by agarose gel electrophoresis and then probes these DNA pieces with a labeled DNA probe that is known to hybridize to all the known alleles of one particular gene. Analyze the indicated lanes of this DNA gel and determine what conclusion can be drawn. Who is the boy’s father?

A. H

B. 1

C. 2

D. 3

E. None of these

F. We cannot tell .

D. 3

8

An experimenter obtains tissue samples from a normal 80-year-old patient and a normal 25-year-old patient and grows fibroblasts from these samples in an in vitro cell culture system. She finds that cells from the older patient stop dividing much sooner than cells from the younger patient. This finding is most likely explained by a difference in which of the following?

A. circulating levels of cytokines       

B. growth factor activity      

C. hormonal levels       

D. oncogene expression

 E. telomere length                 

F. levels of tumor suppressors      

G. we have no explanation

E. Telomere Lenght

9

Which kind of DNA repeat could be part of a cancerous change in which its genetic information is activated to produce an unwanted reverse transcriptase?

A. An ALU SINE

B. A paloindromic tandem repeat

C. A type I LINE

D. A type II LINE

E. The telomere

C. A type I line. 

10

A mutation in a beneficial gut-associated bacterium prevents it from taking it rightful place in the intestinal flora. When this mutation is studied in the molecular biology lab, it is discovered that the problem lies in DNA replication. Careful study reveals that during DNA replication, the leading strand is made at the normal rate, but the lagging strand is barely made at all. Most known mutations cause an important protein to malfunction or to be made in very low amounts. Which of these proteins could be the cause of this observed defect in DNA replication?

A. DNA gyrase        

B. DNA polymerase III      

C. DNA polymerase I     

D. the major helicase      

E. DNA polymerase II

F. DNA polymerase a         

G. The Primase        

H. DNA polymerase d          

I. DNA polymerase e

C. DNA Polymerase I 

11

Bacteria contain all but which of the following? 

A. Circular chromosomes

B. Introns

C. Plasmids

D. Topoisomerase I

E. Topoisomerase II

B. Introns

12

 Which statement is correct regarding DNA repeats?

A. The repeating units in DNA repeats are always completely identical copies of each other

B. Repeats represent about 4% of the human genome

C. LINE elements cluster at telomeres

D. Inverted repeats in coding regions may cause hairpin formation in RNA

E. All DNA repeats in the human genome are biologically silent and not associated with any disease.

D. Inverted repeats in coding regions may cause hairpin formation in RNA 

13

The telomere is considered to be what type of highly repeated DNA sequence?

A. Satellite

B. Minisatellite

C. Microsatellite

D. Tandem

B. Minisatellite

14

The following is a group of statements that putatively describe type I LINEs. Which combination of these statements is TRUE?      

(I) they replicate through an RNA intermediate

(II) they utilize reverse transcriptase for replication

(III) they contain introns

 (iv) they are much more plentiful than Type II LINES

 

A. I, II & IV             B. I, II & III          C. only I & II         D. only I & III      

E. only I & IV       F. I, II, III & IV      G. only II

A. I, II, & IV

15

After an exhaustive digestion of nuclear DNA with micrococcal nuclease, the majority of DNA is protected from digestion. It remains as double-stranded DNA fragments firmly bound to which of the following?

A. histone H1          

B. histone H2A and H2B      

C. the nucleolus      

D. the topoisomerase    

E. an octamer of basic histone proteins          

F. a complex of DNA polymerase and helicase

E. An octamer of basic histon proteins

16

What type of chromatin is inactive and viewed in a micrograph of an interphase nucleus as dense dark clusters of protein and DNA?

A. heterochromatin         

B. sister chromatids       

C. homologous chromosomes       

D. 10 nm fiber

E. 30 nm fiber          

F. euchromatin

A. hererochromatin

17

Which one of these statements describes a very important difference between DNA polymerases and RNA polymerases?

A. RNA Polymerase requires a primer, DNA Polymerase does not.

B. DNA Polymerase requieres a primer, RNA Polymerase does not

C. They both need primers and there is no difference between them. 

D. RNA Polymerase is faster than DNA Polymerase

B. DNA Polymerase Requires a primer, RNA polymerase does not. 

18

What is the purpose of a primer during the process of DNA replication?

A. Provides a 3' OH group to which nucleotides are added

B. Provides a 5' OH gorup to which nucleotides are added. 

C. Its needed for RNA Polymerase to start transcription

D. A primer is optional for DNA Polymerase

A. Provides a 3' OH group to which nucleotides are added. 

19

Histone proteins are rich in what two amino acids?

 A. the aromatic amino acids – tryptophan and phenylalanine

 B. negatively charged amino acids – such as glutamate and aspartate

 C. guanine and leucine

 D. inosine and alanine

 E. the positively charged amino acids – arginine and lysine

 F. polar amino acids – such as glutamine and asparagine

E. The positively charged amino acides- Arginine and Lysine

20

After the digestion of nuclear DNA with micrococcal, the 146 bp DNA fragment found after isolating the nucleosomes and treating them with a high concentration of salt is the: 

A. DNA Connecting the nucleosomes

B. DNA wrapped around the nucleosomes

C. H1 Histone

D. Chromosomal scaffold. 

B. DNA wrapped around the nucleosomes. 

21

How many replication forks form up when a bacteria replicates its chromosome?

A. 1     

B. 2     

C. 3     

D. 4     

E. 8     

F. Hundreds

B. 2

22

How many replication forks are formed when a human cell replicates all its chromosomal DNA? 

 

A. 1

B. 2

C. 3

D. 4

E. 8

F. Hundreds

G. Thousands

H. Several Hundred Thousands. 

H. Several Hundred Thousands. 

23

Which one of the following statements is true about the helicases?

A. Rewind: the two template strands after they have been completed replicated. 

B. Unwind positive supercoils

C. Assemble the replisome

D. Consume ATP 

D. Consume ATP 

24

Mammalian DNA Polymerase alpha are involved in: 

A. Priming and partial synthesins of the lagging strand

B. DNA Repair

C. Replicates mitochondrial DNA

D. Removal of oikazaki fragments. 

A. Priming and partial synthesis of the lagging strand. 

25

A dideoxy ribonucleotide differs from a deoxyribonucleotide only by:

 

A. incorporation of inosine instead of thymine

B. incorporation of uracil instead of thymine

C. incorporation of thymine instead of uracil

D. lack of a 2’ hydroxyl

E. lack of a 3; hydroxyl

E. Lack of a 3; Hydroxyl

26

In prokaryotes, the sliding clamps for the DNA polymerases are simply composed of the g- and b-subunit of the protein complex. However, in eukaryotes, the sliding clamp is largely composed of which one of these important proteins (shown as the abbreviation usually used to name them)?

A. DNA A        

B. SSB             

C. RFC            

D. PCNA         

E. GAPDH       

F. GSK

D. PCNA

27

Which enzyme stitches together the small pieces of DNA on the lagging strand?

A. helicase       

B. ligase          

C. gyrase         

D. phosphodiesterase   

E. DNA kinase

B. Ligase

28

What is wrong with the following statement:  “Reverse transcriptase was first understood through the study of RNA viruses. They have three enzymatic activities that help them invade their host, but they have no proofreading capability.”

A. Reverse Transcriptase was found in DNA viruses

B. Reverse Transcriptase also expresses an RNA-dependent RNA polymerase activity, a 4th enzymatic acivity

C. Reverse Transcriptase does have proofreading capability

D. There is really nothing wrong with the statement

D. There is really nothing wrong with the stament.

29

Telomerase is a special version of a Reserve Transcriptase that uses a … (1) … template to solve the … (2) …. Problem.

A. (1) DNA (2) end replication problem

B. (1) RNA (2) End replication problem. 

C. (1) RNA (2) t-loop problem

D. (1) DNA (2) t-loop problem

B. (1) RNA (2) End replication problem. 

30

 What is the sequence of the TEMPLATE DNA from which the following DNA was obtained in a sequencing reaction?

A.  ACCGTACATTAAA

B.  TGGCATGTAATTT

C.  TTTAATGTACGGT

D.  TTTAATGGACGAT

E.  AAATTACATGCCA

C.  TTTAATGTACGGT