Microbiology Chapter 7, 8 HW

Part 1: The average amino acid length of proteins in Escherichia coli is 235. Therefore, according to the video, the elongation time for an average E. coli protein would be about _____ seconds. - 10 - 470 - 2 - 15 - 235 - 0.3

15 A general rule is that a major advantage for bacteria is their ability to do things quickly, and this also applies to making proteins. The longest known E. coli protein, the RNA-processing enzyme RNaseT, is 1,538 amino acids long and would therefore take about 96 seconds to go through the elongation phase.

Part 2: According to the video, it would take _____ GTP molecules to synthesize a protein 100 amino acids in length. - 0 - 100 - 200 - 101 - 198 - 99 - 202

200 Although there are only 99 peptide bonds formed, adding up all the GTPs used results in double the amount of GTPs as there are amino acids. This is a lot of energy, which emphasizes how important protein synthesis is to cells.

Which of the following may be present as part of the prokaryotic genome? Choose one or more: A. chromosome B. plasmid C. prophage D. RNA

A, B, C

During rolling-circle replication, RepA binds to the ori and nicks one strand of the DNA. The _________ end of the nicked DNA serves as a primer and is extended by DNA polymerase, while the _________ end is coated with single-stranded DNA-binding proteins and replicated using RNA and DNA polymerases. 3' OH or PO4 5' OH or PO4

3' OH the 3' OH end serves as a primer to begin synthesis of the complementary strand. 5' PO4 the 5' PO4 end will be protected by single-stranded DNA-binding proteins until it is replicated by host DNA and RNA polymerases.

Which best describes a genome? Choose one: A. all the genetic information possessed by a cell or virus B. the number of chromosomes present in a cell C. any double-stranded DNA (dsDNA) molecule D. the nucleotide sequence of a given gene E. the dry weight of an organism's total nucleic acid

A An organism's genome includes genes that code for products (e.g., a protein) and noncoding regions, such as regulatory sequences.

Which of the following genes would most likely not be carried by plasmids? Choose one: A. ribosomal RNA genes B. genes involved in nitrogen-fixing C. genes that encode for toxins or other virulence factors D. antibiotic-resistant genes

A Essential genes are located on the bacterial chromosome, not a plasmid, to ensure inheritance.

The plasmid encoded ParR and ParM proteins are involved in Choose one: A. plasmid partitioning. B. bidirectional plasmid replication. C. maintaining plasmids at a high copy number. D. antibiotic resistance.

A ParR and ParM help ensure that low-copy number plasmids are inherited by both daughter cells after bacterial cell division.

Most sigma factors are highly conserved and help RNA polymerases identify the beginning of genes. They accomplish this by binding to which of the following sites on promoters? Choose one: A. -10 and -35 sites B. +10 and +35 sites C. -1 and +35 sites D. +1 and +35 sites E. -1 and +10 sites F. +1 and +10 sites

A The -10 and -35 sites are consensus sequences that interact with different regions of sigma factors. When the sigma factor binds, it interacts with the core RNA polymerase to position the enzyme properly to begin transcription at the +1 site, the start of the RNA transcript.

DNA is __________ into mRNA and mRNA is _________ into proteins. Choose one: A. transcribed; translated B. replicated; hydrolyzed C. translated; replicated D. translated; transcribed

A The central dogma of molecular biology states that DNA is transcribed into mRNA, which is translated into proteins. The DNA to RNA step is called transcription because DNA is used as a template to make a complementary mRNA. The mRNA to protein step is called translation because the language of nucleotides is translated into the amino acid sequence of a protein. For more information, see the chapter introduction.

Sigma factors are necessary in which phase of transcription? Choose one: A. Initiation B. Elongation C. Activation D. Termination

A The sigma factor is needed only for initiation and dissociates from the core RNA polymerase after initiation.

Various sigma factors play a role in gene expression by Choose one: A. using alternate nucleotides to promote different genes. B. binding to a variety of different -10 and -35 sequences. C. bringing about an early termination due to hairpins in the message. D. allowing for binding of various enhancer proteins to aid initiation.

B Different sigma factors recognize the different promoters present in a genome and guide the binding of the RNA polymerase.

Which of the following is not a mechanism by which plasmids ensure their inheritance and maintenance during cell division? Choose one: A. carrying self-preservation genes, known as addiction modules B. low-copy-number plasmids C. carrying partitioning system genes, parC, parM, and parR D. high-copy-number plasmids E. carrying antibiotic resistance genes

B Low-copy-number plasmids have a low probability of being inherited by both daughter cells by random chance.

Sigma factors are responsible for Choose one: A. mRNA binding to promoter regions. B. binding of RNA polymerase to consensus sequences on DNA. C. helping replicate the DNA helix. D. nonselective binding of RNA polymerase to DNA.

B Sigma factor guides RNA polymerase to promoter regions of genes.

Part 2: Which of the following statements is true about the rolling-circle mechanisms of plasmid replication? Choose one: A. RepA nicks the single-stranded RNA plasmid. B. RepA nicks the single-stranded DNA plasmid. C. RepA nicks one strand of the double-stranded DNA plasmid. D. RepA nicks both strands of the double-stranded DNA plasmid.

C RepA nicks one strand of the double-stranded DNA plasmid and holds on to the 5′ end.

Which of the following is the enzyme complex that catalyzes transcription in bacterial cells? Choose one: A. RNA-dependent RNA polymerase B. RNA-dependent DNA polymerase C. DNA-dependent RNA polymerase D. protein-dependent DNA polymerase E. protein-dependent RNA polymerase F. DNA-dependent DNA polymerase

C The DNA serves as the template in order to transcribe RNA, so it is called a DNA-dependent RNA polymerase. There are other types of polymerases that can be used by viruses to make DNA or RNA from an RNA template. One example would be reverse transcriptase used by the HIV virus to make a DNA copy of the viral RNA that invades the cell. This would be an RNA-dependent DNA polymerase.

Part 3: How is the small ribosomal unit positioned to allow for translation to start at the proper start codon? Choose one: A. The small ribosomal subunit starts at the far 5' end of mRNA where the start codon is located. B. The start codon sequence is specifically attracted to the P site. C. Shine-Dalgarno sequence D. Initiation factors position the mRNA accordingly.

C The Shine-Dalgarno sequence is complementary to a sequence on the 16S rRNA of the 30S ribosomal subunit. This sequence is located four to eight bases upstream of the start codon, and the mRNA binding to the 16S rRNA positions the start codon precisely in the P site.

Which of the following may possess an RNA genome? Choose one: A. bacteria B. eukaryotes C. prions D. viruses E. archaea

D All cellular organisms (i.e., bacteria, archaea, and eukaryotes) possess genomes encoded by DNA. Viruses are noncellular organisms that may have either RNA or DNA genomes—but never both. Prions are infectious proteins and do not contain a nucleic acid genome.

Which of the following is NOT true concerning all plasmids? Choose one: A. They may contain antibiotic resistance genes. B. They may be transmitted horizontally from one bacterium to another. C. They may exist in multiple copies in a single cell. D. They are always linear DNA.

D Statements a, b, and c are all true of plasmids, but d may or may not be true.

Rolling-circle replication of plasmids proceeds Choose one: A. in opposite directions from multiple origin sites. B. in opposite directions from a single fixed origin. C. in one direction from multiple origin sites. D. in one direction from a single fixed origin.

D While replication of many plasmids proceeds bidirectionally from a single origin (in a manner similar to that of the bacterial chromosome), other plasmids are capable of unidirectional replication from a single fixed origin. This mode of replication (termed "rolling-circle replication") also occurs during conjugative transfer of plasmids to other cells (Chapter 9).

Part 1: While plasmid replication is not tied to chromosomal replication, many of the proteins used for plasmid replication are host enzymes. Each plasmid contains its own origin of replication (ori) and only the few genes needed for replication. Which of the following proteins is needed for the rolling-circle mechanism of plasmid replication and is encoded by a plasmid gene? Choose one: A. single-stranded DNA-binding protein B. DNA polymerase III (Pol III) C. DNA ligase D. ParC E. RepA

E RepA is encoded by a plasmid gene and is an initiator protein for rolling-circle replication.