Microbiology

Chapter 9

1. What term is defined as a certain segment of DNA that contains the necessary code to make a protein or RNA molecule?

A) Genome

B) Chromosome

C) Gene

D) Nucleotide

E) Plasmid

2. What statement regarding procaryotic and eucaryotic chromosomes is incorrect?

A) Most bacteria have a single, circular chromosome

B) Eucaryotic chromosomes are located in the nucleus, which the procaryotic chromosome is located in the periplasm

C) Extra chromosomal DNA can be found in both procaryotic and eukaryotic cells

D) Eucaryotic chromosomes can number from a few to several hundred

E) The chromosomes of both procaryotes and eucaryotes are subdivided into genes

3. Which statement regarding the structure of a DNA molecule is incorrect?

A) The general double helix structure of DNA is universal (with the exception of some viruses that contain ssDNA)

B) DNA is composed of the nitrogenous bases adenine, thymine, guanine, and cytosine

C) DNA is antiparallel

D) The nitrogenous bases of the two strands are linked by hydrogen bonds

E) The sequence of base pairs along the DNA molecule is invariant

4. What enzyme is responsible for coiling the chromosome into a tight bundle by introducing a reversible series of twists into the DNA molecule?

A) DNA gyrase

B) Helicase

C) Ligase

D) Primase

E) DNA polymerase I

5. Why is DNA replication said to be semiconservative?

A) A single copy of DNA is made from the (-) strand

B) The products of replication are one double helix containing all parental DNA and one double helix containing all daughter DNA

C) The enzyme DNA polymerase III copies the parent strands

D) The products of replication are two double helices, each of which contains one parent and one daughter strand

E) DNA replication is bidirectional on the bacterial replicon

6. Which statement concerning DNA polymerase III is incorrect?

A) It requires the double helix to be unwound and that the individual strands are separated

B) It can only add nucleotides to the 3' end of an existing nucleotide

C) It can only add nucleotides in the 5' to 3' direction

D) It synthesizes the leading strand discontinuously and the lagging strand continuously

E) It is a huge enzyme complex

7. What enzyme is responsible for detecting incorrect, unmatched bases, for excising them, and for replacing them with the correct base?

A) DNA gyrase

B) DNA polymerase III

C) Primase

D) Ligase

E) Helicase

8. What determines the phenotype of a cell?

A) Its DNA

B) Its proteins

C) Its RNA

D) Its ribozymes

E) Its triplet code

9. The transcription of what molecule is similar to leading strand synthesis in DNA replication?

A) mRNA

B) tRNA

C) rRNA

D) Primer

E) Ribozymes

10. Although the nucleotide sequence of promoters can vary, what is similar about all promoter regions?

A) They are just distal to the beginning of the gene to be transcribed

B) They are made up of four sequences of DNA

C) They are rich in adenine and thymine nucleotides

D) They are recognized by DNA polymerase III

E) They are responsible for synthesizing the template strand of DNA

11. The enzymes required for the formation of a peptide bond between adjoining amino acids in a protein are supplied by what structure?

A) mRNA

B) Charged tRNAs

C) Small ribosomal subunit

D) Large ribosomal subunit

E) The E site on a ribosome

12. Why can't the nucleotide sequence of DNA be derived by examining a protein's primary structure?

A) Because the genetic code is redundant.

B) Because the genetic code is not universal.

C) Because each amino acid has a different codon in all organisms.

D) Because it is impossible to determine the anticodon of the tRNA.

E) Because posttranslational modification of a protein changes its original primary structure.

13. The coding regions of eucaryotic mRNA molecules are known as what?

A) Spliceosomes

B) Split genes

C) Introns

D) Pre-mRNA

E) Exons

14. The late phase of dsDNA viral replication includes which event?

A) Viral DNA enters the nucleus

B) Viral DNA is replicated in the nucleus

C) Viral mRNA is translated into proteins necessary for viral DNA replication

D) Genes for the viral capsid and other structures are transcribed

E) Genes coding for enzymes important in viral DNA replication are transcribed

15. Viruses containing what type of nucleic acid can become silently integrated into the host's genome?

A) ssRNA (+)

B) ssDNA

C) dsDNA

D) dsRNA

E) ssRNA (-)

16. Following viral penetration and uncoating in RNA viruses, what possible form of genetic message is ready to be translated directly into proteins?

A) ss (+) sense genome

B) ss (-) sense genome

C) ds RNA

D) ssRNA → ssDNA → dsDNA

E) Close, circular RNA

17. Along with the ssRNA nucleic acid, retroviruses also contain what enzyme within the viral capsid?

A) Helicase

B) RNA polymerase I

C) DNA polymerase III

D) Oncogenase

E) Reverse transcriptase

18. Within an inducible operon, transcription is prevented by the presence of what?

A) The operator

B) The repressor

C) The activator

D) The promoter

E) The inducer

19. In a repressible operon, transcription is halted when what event occurs?

A) The corepressor activates the repressor so that the repressor can bind to the operator

B) The corepressor is in high demand by the cell

C) The inducer attaches to the repressor so that the repressor can bind to the operator

D) The repressor alone binds to the operator

E) The corepressor binds to the inducer which activates the repressor so the repressor can bind to the operator

20. Which mutation changes a normal codon into a stop codon?

A) Silent mutation

B) Back mutation

C) Nonsense mutation

D) Missense mutation

E) Point mutation

21. What mutational outcome leads to the placement of a different amino acid in a protein?

A) Back mutation

B) Silent mutation

C) Nonsense mutation

D) Missense mutation

E) Point mutation

22. What accounts for the development of a silent mutation?

A) A back mutation

B) Excision repair

C) The redundancy of the genetic code

D) Evolution

E) Photoreactivation

23. What did Francis Griffith's experiments with Streptococcus pneumoniae and laboratory mice demonstrate?

A) Plasmids were present in bacteria

B) Bacteria could be transformed by the DNA of other bacteria

C) Bacteria could be infected with viruses

D) Encapsulated bacteria are more virulent than nonencapsulated strains

E) Eucaryotes could be transfected with bacterial DNA

24. What is the process of genetic recombination in which a highly specific portion of the host genome is regularly incorporated into a virus?

A) Transfection

B) Conjugation

C) Generalized transduction

D) Transformation

E) Specialized transduction

25. Which of the following is not an outcome of the movement of transposons?

A) Replacement of damaged DNA

B) Changes in phenotypic traits

C) Creation of retroviruses

D) Intermicrobial transfer of drug resistance

E) Creation of different genetic combinations which are necessary for high levels of variation in some proteins