Chapter 8 – Bacterial Genetics & Gene Expression

Question-and-Answer flashcards covering gene structure, plasmids, DNA replication, transcription, translation, gene regulation, mutations, DNA repair, and key biotechnology tools from BIO3310 Chapter 8.

What is the basic definition of a gene?

A unit of information encoded by DNA that can be expressed to form an RNA product.

What DNA control sequence determines when a gene is expressed?

The promoter.

How are bacterial coding regions different from eukaryotic coding regions?

Bacteria generally lack introns; their genes are mostly continuous coding regions, whereas eukaryotic genes contain introns and exons.

What are plasmids?

Small, circular, extrachromosomal DNA molecules that replicate independently of the bacterial chromosome.

Can plasmids enter or exit a bacterial cell without changing the species identity?

Yes, plasmids may enter or exit a bacterial cell without altering its species classification.

Name two kinds of genes commonly carried on plasmids.

Virulence factors and antibiotic-resistance genes.

List the six ESKAPE pathogens.

Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species.

What model describes the mechanism of bacterial DNA replication?

Semiconservative replication, where each daughter DNA molecule contains one parental and one newly synthesized strand.

What are the three stages of DNA replication?

Initiation, elongation, and termination.

During initiation of DNA replication, where does synthesis begin?

At the origin of replication (oriC).

Which enzyme synthesizes the short RNA primer needed for DNA replication?

Primase.

In which direction does DNA polymerase synthesize DNA?

5′ → 3′ direction.

What is the difference between leading and lagging strand synthesis?

The leading strand is synthesized continuously, while the lagging strand is synthesized discontinuously in Okazaki fragments.

Which enzyme seals the nicks between Okazaki fragments?

DNA ligase.

Which enzyme introduces negative supercoils after replication?

DNA gyrase.

What must occur for a gene to be expressed?

RNA polymerase must transcribe the DNA into RNA.

What is an operon?

A promoter and the adjacent genes it controls, usually encoding proteins with related functions.

What subunit of RNA polymerase recognizes the promoter in bacteria?

Sigma factor.

At which codon does translation normally start?

AUG, which encodes methionine.

Name the three stop codons.

UGA, UAA, and UAG.

What is the role of transfer RNA (tRNA) during translation?

tRNA transports specific amino acids to the ribosome, matching its anticodon with mRNA codons.

Identify the three ribosomal tRNA-binding sites.

A site (acceptor), P site (peptidyl), and E site (exit).

Which factor brings a charged tRNA to the A site during elongation?

Elongation factor EF-Tu bound to GTP.

What triggers termination of translation?

A stop codon in the mRNA recruits a release factor to the A site, releasing the peptide chain.

Why must bacteria regulate gene expression?

To conserve energy by producing proteins only when needed.

Which level of gene regulation is most difficult to reverse?

Changing the DNA sequence (e.g., phase variation).

Define a missense mutation.

A point mutation that changes a codon, resulting in a different amino acid in the protein product.

Define a nonsense mutation.

A point mutation that converts a codon to a stop codon, prematurely terminating translation.

What is a silent mutation?

A base-pair substitution that changes a codon but still encodes the same amino acid.

What happens in a frameshift mutation?

Insertion or deletion of base pairs shifts the reading frame, altering downstream amino acids.

What is SOS repair?

A last-resort, error-prone DNA repair system that introduces mutations to save the cell under severe damage.

What do restriction endonucleases do in biotechnology?

They recognize specific DNA sequences and cut the DNA at those sites.

Define recombinant DNA.

A DNA molecule that contains sequences from different source organisms.

What is the purpose of a vector in recombinant DNA technology?

To carry and replicate the DNA sequence of interest, commonly using plasmids or viral genomes.

What is transformation in molecular biology?

Uptake of recombinant plasmid DNA by microbial cells.

What does the polymerase chain reaction (PCR) accomplish?

It amplifies specific DNA sequences, enabling detection of pathogens or resistance genes.

Which statement about plasmids is FALSE according to the lecture?

Plasmids are essential for survival of the organism.

Which enzyme synthesizes a complementary DNA strand during replication?

DNA polymerase.

Which codon-level gene regulation strategy did the lecture cite as the most drastic?

Changing the DNA sequence itself.