6 Microbial Genetics Free Online FlashCards

What does semiconservative DNA replication produce?

Each new double-stranded DNA molecule contains one original strand and one newly synthesized strand.

How do leading- and lagging-strand synthesis differ?

The leading strand is synthesized continuously toward the replication fork; the lagging strand is made in Okazaki fragments that DNA ligase joins.

How do transcription and translation differ?

Transcription copies DNA information into RNA; translation uses mRNA codons to assemble a polypeptide.

Why can bacterial transcription and translation happen simultaneously?

They can occur simultaneously because bacteria lack a nucleus separating DNA from ribosomes.

What is a bacterial operon?

An operon is a group of related genes controlled by shared regulatory DNA and transcribed into one mRNA.

How can an insertion or deletion cause a frameshift?

A frameshift can occur when an insertion or deletion in a protein-coding sequence is not a multiple of three, changing downstream codons.

What effects can a mutation have on a gene?

A mutation may have no detectable effect, alter a protein’s function, or change how much gene product is made.

How does natural selection affect beneficial bacterial variants?

Mutations do not arise because a bacterium needs a trait. If a variant improves reproductive success in an environment, natural selection can increase its frequency.

How do repressors and activators affect transcription?

Repressors reduce transcription by binding regulatory DNA; activators increase transcription by helping RNA polymerase initiate it.

When is lac operon expression strongest?

The lac operon is expressed most strongly when lactose is available and glucose is scarce: the inducer reduces LacI binding, while cAMP-bound CAP helps RNA polymerase.

How does tryptophan regulate the trp operon?

When tryptophan is plentiful, it helps activate a repressor that shuts down transcription; when tryptophan is scarce, repression is relieved.

What is bacterial transformation?

Transformation occurs when a competent bacterial cell takes up free DNA from its surroundings.