MIC102 Unit 2 Quiz Answers

UCD WQ2025

T/F: Filamentous temperature-sensitive mutations in the fts genes cannot divide normally at 42°C and instead produce long filaments, but can divide normally at 37°C.

True

Why do ftsZ mutants that produce long filaments die?

Because they become too large and face problems with their surface:volume ratio

Which of the following methods to control microbial growth does not actually kill microbes?

Filtration

Bacterial replication starts at the  ______________ site, with the replication machinery making a replication bubble called __________, and then ends at the _________ site.

ori, theta, ter

What happens if the promoter sequence in a gene is mutated relative to the bacterial promoter consensus sequence?

The mRNA is translated at a lower level

T/F: The ribosome technically does not do the translation from RNA to protein

True

Why would it be advantageous for a bacterium to have the direction of gene transcription be the same as the direction of replication?

To avoid collisions between RNA polymerase and the DNA replication mahinery

If stretched out, the bacterial chromosome would be longer than the length of the cell.

True

T/F: The ribosome technically does not do the translation from RNA to protein.

True

What is the most likely outcome if the promoter sequence of a gene (in DNA) has only one mutation relative to the bacterial promoter consensus sequence?

The mRNA is translated at a lower rate

A sigma factor

Is necessary for RNA polymerase promoter-binding specificity

The E. coli trp operon is sensitive to tryptophan levels in the cell. High levels of tryptophan in the cell

Cause the ribosomes to translate without stalling, forms of a terminator loop

If you were examining an E. coli mutant that had a mutation that severely affected the DNA binding of the LacI repressor, how would transcription of the Lac operon mRNA change, assuming there is lactose but no glucose (i.e. CAP and cAMP are present)?

None because when lactose levels are high the repressor is inactive and the very low level of glucose means CAP enhances transcription to maximal levels

T/F: E coli will use lactose before glucose, its preferred carbon source.

False

Which of the following changes to an E. coli cell would be likely to cause it to be unable to initiate DNA replication? (pick all that apply)

• Deletion of DnaA binding sites in oriC

• Deletion of AT-rich sequences in oriC

• Deletion of the SeqA gene

• Deletion of the ter site

• Deletion of DnaA binding sites in oriC

• Deletion of AT-rich sequences in oriC

• Deletion of the SeqA gene

Using error proofreading by the polymerase, a bacterium can duplicate its genome with an error rate of 1 in a billion base pairs. How many errors should I expect to see in genomes of its two daughter cells after binary fission?

none

You randomly mutate an organism, determine the sequence of the mutated DNA, and compare it to the wild-type. Here are both sequences of DNA, starting at the start codon:

Wild-type:  ATG GTC TGC AGG AAG TAC GCG GCG
Mutant:      ATG GTC TGC AGG AAG TGC GGC GT

What type of mutation have you generated?

Deletion with a frameshift

When doing enrichment screening for histidine auxotrophs, why do we add penicillin?

To increase the proportion of mutants in the flask by killing off wild type cells that are growing

What is a genome?

The complete collection of heritable information stored in DNA of an organism

T/F: Conjugation requires a phage as an intermediate to exchange genes between bacterial cells.

False

Metagenomics is

the study of all the genomes present in one sample (can be environmental source)

T/F: Traditional isolation or culturing techniques are only able to identify less than 1% of bacteria in an environmental sample.

True

You are a graduate student working in a lab. You want to make a mutation in a specific place in the bacterial chromosome. Which would be the best method to use?

CRISPR/Cas9 genome editing

How can mobile elements cause changes in the bacterial genome?

• All the options are correct

• A transposable element can land inside of an existing gene

• A composite transposon can insert a new gene (example: antibiotic resistance gene)

All options are correct

Oxygenic photosynthesis evolved in which of the following groups?

Cyanobacteria

Which bacterial group is known for living in the soil and producing antibiotics.

Actinobacteria

Lactose binds to the lac repressor, causing it to release from the promoter. This is an example of:

Negative control of an inducible gene

T/F: The Plasmodium apicoplast is used to enter red blood cells.

True

How do Spirochetes achieve their spiral shape and corkscrew motility?

They have an axial filament, which is a flagellum inside the periplasm

Which of the following characterizes Actinobacteria?

• All of the answers are correct

• Mostly live in the soil

• Have many antibiotic producing bacteria

• Make a fungus-like mycelium

All of the answers are correct

T/F: Yeast have two different mating types that are required for sexual reproduction, but the mating type can be changed at any point in the cells life.

True

What is the role of the macronucleus in Paramecium cell division?

It contains many copies of growth genes to allow cell division