Microbiology Exam III

Following uptake, transforming DNA becomes attached to a competence-specific protein that prevents it from nuclease attack until it reaches the chromosome. (true or false?)

True

A mutant that has a nutritional requirement for growth is an example of a(n)

auxotroph

. In Sanger sequencing and in many newer sequencing techniques, labeled precursors are used. What are these precursors?

nucleotides that will be incorporated into the newly synthesized DNA

Which of the following features are common to transformation, transduction, and conjugation? (1) unidirectional transfer of genes (2) incomplete gene transfer (3) homologous recombination (4) meiosis occurring in the recipient

1, 2, 3

The genetic code has many important characteristics. For example, a specific codon always means the same thing in a particular species. Codons mean the same thing in most species (even though there are some exceptions). In some cases, a particular amino acid can be specified by more than one codon (the genetic code is degenerate). Which of the following answers describes an example of the degenerate nature of the code?

AUU, AUC, and AUA all code for Ile

What is one of the changes that occurs when a cell contains an F plasmid that is NOT integrated into the chromosome?

Cell surface receptors change, preventing the uptake of more plasmids through conjugation

The SOS regulatory system is activated by

DNA damage.

In DNA replication in vivo, RNA primers are used. However, researchers used DNA primers instead in the lab because DNA primers are more stable. Why might this be the case?

RNA has a relatively short half-life compared with DNA and does not need to be as stable to perform its functions in the cell.

During conjugation, if an Hfr cell is mated with an F- cell, why will the F- cell remain F-?

The cells would not stay in contact long enough for the entire Hfr genome to be transferred.

What would result in a frameshift mutation?

The deletion of two nucleotides in a codon (or an insertion)

Some bacteria have unusually high mutation rates. Is there an adaptive reason why they might have such high mutation rates?

These bacteria may be able to adapt rapidly to a new environment (e.g., an environment with an antibiotic).

Frameshift mutations can be very severe. What is one reason why they are often so serious?

When a frameshift mutation occurs, it causes changes in many bases downstream and can affect many of the amino acids in the protein

One group of chemical mutagens includes the base analogs. How do these lead to mutations?

When replication occurs, complementary base pairing may fail because the base analog may not be treated in the same way as the base that it replaced.

A deleterious mutation in recA results in

a decrease in homologous recombination

A change in the nucleotide sequence of DNA that is passed on to daughter cells is referred to as

a mutation

Which of these organisms is likely to have the largest genome?

a yeast cell

Linking an ORF with a specific function is an example of gene

annotation

Which of the following is NOT required for homologous recombination?

an Hfr chromosome

. F+ strains of Escherichia coli have what?

have the F factor as a plasmid.

Transcriptome analysis is useful in relation to genome analysis because

it analyzes RNA, thus it reveals which genes are expressed under different conditions.

If a bacterium carrying a plasmid that confers resistance to ampicillin is placed into medium without ampicillin, it may

lose the plasmid because there is no selection for ampicillin resistance

You have performed the following mating experiment using Hfr and F-strains of Escherichia coli: Hfr (thr+ leu+ gal+ strs) √ó F- (thr- leu- gal- strr). Which of the following selective media would you use to score recombinant colonies?

minimal medium + streptomycin

The addition of two bases to the genome of a prokaryote would be most damaging if located

near the beginning of the coding region of a protein

Increasing genetic variability by the uptake of DNA from the environment is

transformation

The uptake of free DNA from the environment is referred to as ________, while the transfer of DNA with cell-to-cell contact is known as ________.

transformation / conjugation