Microbial Genetics and Biotechnology Flashcards

Question and answer practice flashcards covering microbial genetics, DNA replication, transcription, translation, operons, gene transfer, mutations, and biotechnology tools.

What is the size and physical length of the Escherichia coli chromosome?

About 4.6 million base pairs ($4.6\,\text{Mbp}$) and $1\,\text{mm}$ long.

What type of plasmid carries genes required for sex pili and the transfer of plasmid DNA?

Conjugative plasmid (F factor).

Who discovered transposons in corn during the 1940s and 1950s, winning the Nobel Prize in 1983?

Barbara McClintock.

In what direction is a newly synthesized strand of DNA formed during replication?

In the $5' \rightarrow 3'$ direction.

Which enzyme is responsible for joining the discontinuous Okazaki fragments on the lagging strand during DNA replication?

DNA ligase.

At what specific DNA sequence does transcription begin when RNA polymerase binds?

The promoter sequence.

What is the start codon for mRNA translation, and which amino acid does it encode?

AUG, which encodes Methionine (Met).

What are the three nonsense (stop) codons that signal the end of translation?

UAA, UAG, and UGA.

How is transformation defined in bacterial horizontal gene transfer?

The process where genes are transferred from one bacterium to another as "naked" DNA in solution.

In Griffith's experiment, what was the outcome when mice were injected with a mixture of living nonencapsulated and heat-killed encapsulated Streptococcus pneumoniae?

The mouse died, and colonies of encapsulated bacteria were isolated from the dead mouse.

How is a High Frequency Recombination (Hfr) cell formed during bacterial conjugation?

When an F factor (a plasmid) becomes integrated into the bacterial chromosome of an F+ cell.

What vehicle transfers genetic material from a donor cell to a recipient cell during bacterial transduction?

A virus vehicle called a bacterial phage (bacteriophage).

What functional units make up the control region and structural region of a bacterial operon?

The control region contains the promoter ($P$) and operator ($O$) sites, followed by structural genes that code for proteins.

In the inducible lactose operon, what compound binds to the repressor protein to turn transcription ON?

Allolactose (inducer).

In the tryptophan repressible operon, what molecule acts as the corepressor to activate the repressor protein and turn transcription OFF?

Tryptophan.

What is the spontaneous mutation rate per replicated base pair in bacteria?

$1$ in $10^9$ replicated base pairs.

What type of mutation occurs when a base substitution converts a sense codon into a stop codon?

Nonsense mutation.

What type of DNA lesion is formed when bacteria are exposed to ultraviolet (UV) light?

Adjacent thymines become cross-linked, forming a thymine dimer.

What bacterial culture is used in the Ames test to evaluate suspected chemical carcinogens or mutagens?

Histidine-dependent Salmonella (an auxotroph requiring histidine).

What are the temperature and duration conditions for the three steps in a single PCR cycle?

1. Incubate target DNA at $94^\circ\text{C}$ for $1\,\text{minute}$ (strand separation); 2. Incubate at $60^\circ\text{C}$ for $1\,\text{minute}$ (primer attachment); 3. Incubate at $72^\circ\text{C}$ for $1\,\text{minute}$ (copy synthesis).