Lecture 13 - Optional Reading
In transformation, only one daughter cell inherits donor DNA. This is because ______.
only a single strand of donor DNA integrates into the recipient chromosome
An actual DNA transformation experiment is set up so that _______ grow under selective conditions.
only transformed cells
A replicon is a DNA molecule that contains a(n) ____
origin of replication
The entire set of genes found in all three strains of this particular species is known as the ______.
pan-genome
A bacterial virus is known as a(n) _______.
phage
Restriction-modification systems of bacteria include what two components?
- A modification enzyme that adds protective methyl groups to the cell's own DNA - A restriction enzyme that recognizes and cuts at a short nucleotide sequence
Which of the following are systems bacteria can use to protect against invading DNA?
- CRISPR - restriction-modification
Specialized transduction ______.
- transfers phage DNA and adjacent host genes - results from errors in excision of the prophage - produces defective phage particles
Examples of conditions where bacteria can become naturally competent in the environment include ______.
- when certain nutrients are scarce - when there is a high density of bacteria
Some types of bacteria become competent ______.
- when there is a high concentration of bacterial cells - when nitrogen or carbon sources are scarce
Place the steps of DNA-mediated transformation into the correct order. Start with the earliest at the top.
1. Double stranded DA molecule binds to surface receptor 2. Nucleases at the cell surface degrade one strand of DNA; the other strand enters the cell 3. ssDNA integrates into genome after entering the cell 4. Strand being replaced by donor DNA is degraded
Place the steps of F plasmid transfer in the correct order. Start with the earliest at the top.
1. F pilus makes contact with recipient cell 2. One strand of F plasmid is cut in origin of transfer 3. Single strand of F plasmid is transferred to the recipient cell 4. Complement of transferred strand is synthesized
In E. coli, less than 50% of the genes are found in all strains. These conserved genes are called the ____ genome
core
When horizontal gene transfer occurs between a donor and recipient cells, the resulting cells are called ____
recombinants
If DNA acquired through horizontal gene transfer is not a replicon, then a process called _____ recombination must occur for that DNA to be passed on to daughter cells.
homologous
CRISPR systems involve ______..
retained segments of phage DNA used by bacteria to recognize and destroy future invading DNA
During conjugation, the F plasmid nucleic acid that transfers is ______.
ssDNA
When DNA is transferred from an Hfr cell to a recipient cell, the recipient _______.
stays an F- cell
Chromosomal DNA is transferred with F plasmid DNA in an Hfr cell because ______.
the plasmid DNA is integrated into the chromosome in these cells
In generalized transduction, donor DNA is mistakenly packaged into a phage coat, forming a _____ particle
transducing
When some species of bacteria reach a certain density or when nutrients are in short supply, they ______.
turn on genes required for competence
Although mobilizable plasmids encode an origin of transfer, they lack other genetic information required for transfer. Under what circumstances can a mobilizable plasmid be transferred to another bacterial cell?
when a conjugative plasmid is present in the same cell
The CRISPR system has been called the immune system of bacteria. It helps protect bacteria from a repeat infection because bacterial cells ______.
integrate phage DNA fragments in their own chromosomes and target for destruction any DNA encountered later that contains the same sequences
In an experiment, donor DNA, DNase, and recipient cells are added to a mixture. The recipient cells are not transformed. This tells us what about the donor DNA?
it is NAKED
Plasmids with a ___ copy number occur in only one copy per cell, while those with a ___ copy number are present in many copies per cell.
low; high
Genes that vary considerably among strains of a species are likely to be ______.
mobile genetic elements
The total set of mobile genetic elements is called a(n)
mobilome
The integration of a region of DNA into a segment that does not have extensive similarity in nucleotide sequence is called ______.
non-homologous recombination
During bacterial conjugation, synthesis of a new strand of F plasmid DNA occurs in ______.
both the donor and recipient
Cells that have the ability to take up DNA from the environment are called ______ cells.
competent
Sources of "naked" DNA
- Secreted into the environment by bacteria - Lysed (burst) bacterial cells
Characteristics of Recombinants
- They result from horizontal gene transfer. - The have properties of both donor and recipient cells.
Which of the following are components of the simplest transposon, an insertion sequence?
- inverted repeats - transposase gene
Some prokaryotes are naturally competent ______.
- only under specific conditions - all the time
The following are examples of mobile genetic elements
- phage DNA - genomic islands - plasmids - transposons
The following can be found in a Bacteriophage
- protein coat - DNA or RNA genome
Generalized transducing particles contain which of the following?
Bacterial genes
How does a modification enzyme protect a bacterial cell from its own restriction enzyme?
By adding methyl groups to the nucleobases of the cell's DNA that are recognized by the restriction enzyme
When integrated F plasmid DNA in an Hfr cell is excised from the chromosome, an excision error can result in the removal of chromosomal DNA along with the F plasmid DNA, creating a plasmid called ______.
F'
Examples of Replicons
Plasmid Chromosome
Homologous Recombination
Process by which a cell replaces a stretch of DNA with a segment that has a similar nucleotide sequence.
Plasmids that encode resistance to a variety of antimicrobial agents and heavy metals are called Blank______ plasmids or factors.
R
A plasmid that can directs its own transfer from donor to recipient cells is called a(n) ____ plasmid
conjugative
DNase is added to a mixture of donor DNA and recipient. If the donor DNA is naked, what will happen?
The recipient will be unable to acquire that DNA via transformation.
The easiest way to detect if streptomycin sensitive (StrS) cells are transformed with DNA from streptomycin resistant cells (StrR) is by growing the cells on ______.
a medium containing streptomycin
