Ch. 7 HW

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 ; 5'PO4 During rolling-circle replication, RepA binds to the origin and nicks one strand of the DNA. RepA holds on to the 5' phosphate end, while the 3' hydroxyl end serves as a primer for host DNA polymerase (DNA Pol III). The 5' PO4 end is coated with single-stranded DNA-binding proteins and eventually replicated using RNA and DNA polymerases.

Identify which of the following statements are true about an operon. Choose one or more: A. Multiple protein products can be produce by a single operon. B. Operons produce monocistronic messages. C. All genes in an operon are controlled by a single promoter. D. Multiple RNA molecules are produced by a single operon.

A. Multiple protein products can be produced by a single operon. C. All genes in an operon are controlled by a single promoter. Most prokaryotic genes are organized in coordinately regulated, multiple-gene operons. Operons contain multiple genes but are controlled by a single regulatory sequence, called a promoter. Operons produce a single, polycistronic RNA molecule that can encode for multiple protein products.

Identify which of the following are examples of horizontal gene transfer. Choose one or more: A. a bacterium obtaining an antibiotic resistance gene via conjugation B. a bacterium taking up a virulence gene via transformation C. a protozoan obtaining a gene that encodes for a metabolic enzyme from a bacterium via phagocytic endocytosis D. a protozoan passing on a gene that encodes for a metabolic enzyme to its offspring

A. a bacterium obtaining an antibiotic resistance gene via conjugation B. a bacterium taking up a virulence gene via transformation C. a protozoan obtaining a gene that encodes for a metabolic enzyme from a bacterium via phagocytic endocytosis Horizontal gene transfer (HGT) is the movement of genetic information from one cell to another. Mechanisms of horizontal gene transfer in bacteria include conjugation, transformation, and transduction. The study of horizontal gene transfer in bacteria ultimately led to the discovery of horizontal gene transfer throughout animals and plants.

Which of the following is not a mechanism of horizontal gene transfer in bacteria? A. binary fission B. transduction C. conjugation D. transformation

A. binary fission Conjugation, transduction, and transformation are all mechanisms of horizontal gene transfer in bacteria. Binary fission is a mechanism of asexual reproduction whereby the parental cell divides to produce two daughter cells. During the process of binary fission there is no transfer of genetic information between cells and no opportunity for genetic diversity.

Which of the following are possible structural forms of bacterial and archaeal chromosomes? Choose one or more: A. circular DNA chromosomes B. circular RNA chromosomes C. linear DNA chromosomes D. linear RNA chromosomes

A. circular DNA chromosomes C. linear DNA chromosomes Genomes of bacteria and archaea are made up of chromosomes and plasmids consisting of DNA. While most prokaryotic chromosomes are circular, some prokaryotic chromosomes are linear. In contrast, eukaryotic chromosomes are only linear.

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

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

Which sequence shows increasing numbers of genes? A. Gene, regulon, operon B. Gene, operon, regulon C. Operon, regulon, gene D. Operon, gene, regulon

B. Gene, operon, regulon An operon contains a number of genes in tandem and a regulon comprises operons that have a common biochemical purpose.

Which statement concerning the genomes of organisms is true? A. All organisms have roughly the same DNA content. B. Organisms differ in their genome size. C. Archaeal genomes are larger than bacterial genomes. D. Organisms differ in DNA content but contain roughly the same number of genes.

B. Organisms differ in their genome size. Genome size and gene number vary widely among organisms. The sizes of both bacterial and archaeal genomes vary widely, with much overlap between the two.

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

B. They are always linear DNA. Statements A, C, and D are all true of plasmids, but B may or may not be true.

Which of the following is an example of horizontal gene transfer in bacteria that requires cell-to-cell contact? A. transformation B. conjugation C. transduction D. binary fission

B. conjugation Horizontal gene transfer is the movement of genetic information, DNA, from one cell to another. Conjugation, transformation, and transduction are all examples of horizontal gene transfer in bacteria. However, conjugation is the only example of horizontal gene transfer that requires direct contact between bacterial cells. This direct contact is typically initiated by a special pilus protruding from a donor cell (discussed further in Ch. 9).

Bacterial genomes A. are several linear chromosomes. B. depend on the species. C. are a single circular chromosome. D. are several circular chromosomes.

B. depend on the species. While a single circular chromosome as in E. coli is common, other bacteria contain multiple circular or even linear chromosomes.

Which of the following are extragenomic DNA molecules that commonly interact with bacterial genomes? Choose one or more: A. eukaryote-specific plasmids, such as 2µ in Saccharomyces cerevisiae B. horizontally transferred bacterial plasmids C. mitochondrial genomes D. bacteriophage genomes

B. horizontally transferred bacterial plasmids D. bacteriophage genomes The two kinds of extragenomic DNA molecules that frequently integrate into bacterial genomes include plasmids and bacteriophage genomes. Bacteria can acquire these extragenomic DNA molecules via conjugation, transformation, and transduction. Plasmid-encoded functions often contribute to the physiology of the cell (for example, antibiotic resistance).

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

B. ribosomal RNA genes Plasmids are much smaller than chromosomes and are found in archaea, bacteria, and eukaryotic microbes. While plasmids often carry genes that may benefit the host under certain conditions, such as antibiotic resistance, most essential genes that are required for normal cell function and survival (such as ribosomal RNA genes, which make products required for translation) must be carried on the chromosome to ensure that these genes are inherited by their daughter cells.

Functional units of DNA sequences include structural genes and DNA control, or regulatory, sequences. Which of the following is an example of a structural gene? A. enhancer binding site B. sequence that encodes for an RNA molecule C. transcription factor binding site D. promoter sequence

B. sequence that encodes for an RNA molecule Structural genes are nucleotide sequences that can be transcribed to produce a functional RNA transcript. DNA control sequences, including promoters and binding sites for regulatory proteins, regulate the expression of structural genes.

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

C. RepA nicks one strand of the double-stranded DNA plasmid. During rolling-circle replication, RepA bind to the origin and nicks one strand of the DNA. RepA holds on to the 5' end, while the 3' end serves as a primer for host DNA polymerase (Pol III).

A structural gene is A. an enzyme involved in the conversion of DNA into RNA. B. an organism's entire genetic complement of DNA. C. a string of nucleotides that can be used as a template to produce an RNA that codes for a protein. D. a string of nucleotides that can be decoded by an enzyme to produce a protein.

C. a string of nucleotides that can be used as a template to produce an RNA that codes for a protein. A gene is a string of nucleotides (DNA in cells) that can be transcribed to produce an RNA molecule. The RNA produced may be the end produce (e.g., tRNAs) or may be further translated into a protein. An organism's entire complement of DNA is its genome.

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? A. DNA polymerase III (Pol III) B. DNA ligase C. single-stranded DNA-binding protein D. RepA E. ParC

D. RepA RepA is encoded by a plasmid gene and is an initiator protein for rolling-circle replication. During rolling circle-replication, RepA binds to the origin and nicks one strand of the DNA. RepA hold on to the 5' end, while the 3' end serves as a primer for DNA polymerase. RepA is also responsible for recruiting host DNA helicase as well as rejoining the nicked strands.

Which of the following is an example of horizontal transmission? A. Mitosis B. PCR C. Cell division D. Transformation

D. Transformation Horizontal transmission is the passage of genes from one organism to another via a non-reproductive process. This transfer can be accomplished via transformation. Mitosis is the division of the chromosome sets in eukaryotes prior to cell division. Cell division then distributes the DNA to the offspring of the original cell, which is an example of vertical transmission. PCR is a technique to amplify a specific DNA fragment.

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

D. low-copy-number plasmids Low-copy-number plasmids limit how many copies they make to avoid using excess cellular energy. However, these low-copy-number plasmids must also have partitioning systems to ensure that both daughter cells inherit the plasmid. One of these partitioning systems includes the plasmid-encoded genes parC, parM, and parR.

Eukaryotic genomes comprise mostly _________________, whereas prokaryotes have mostly __________________. A. circular DNA: linear DNA B. double-stranded DNA; single-stranded DNA C. positively supercoiled DNA; negatively supercoiled DNA D. noncoding DNA; coding DNA

D. noncoding DNA; coding DNA Whereas eukaryotic genomes contain much noncoding DNA, prokaryotic genomes have little noncoding DNA. Eukaryotes usually have linear chromosomes and bacteria usually have circular chromosomes. Both eukaryotes and prokaryotes have double-stranded DNA that is negatively supercoiled.

Fill in the blank: Functional units of DNA sequences include structural genes, which are nucleotide sequences that encode an RNA molecule, and ___________________ sequences that regulate the expression of structural genes.

DNA control DNA control sequences, or regulatory sequences, regulate RNA production of an adjacent structural gene. These sequences are not considered genes because they do not encode for an RNA molecule or protein. Examples of DNA control sequences include promoters and regulatory protein-binding sites.

A collection of prokaryotic genes and operons located at different positions on a chromosome but that have a unified biochemical function is known as a ______________.

regulon While genes of an operon are situated head to tail on a chromosome and controlled by a single promoter, several genes and operons located at different chromosomal positions can produce products that have a unified function, such as amino acid synthesis or metabolic pathways. The collection of these genes and operons is known as a regulon. All genes within a regulon are regulated by the same regulatory proteins.