MCB Midterm 2

The Watson-Crick model of DNA shows that the base adenine pairs with:

thymine while cytosine pairs with guanine

Where does the complex of RNA polymerase and Sigma factor bind to initiate transcription in Bacteria?

promoter region of a gene

DNA and RNA are both used in every living cell. What makes them different?

All statements are true (RNA contains ribose and DNA contains deoxyribose, RNA is single-stranded and DNA is double stranded, RNA contains the base uracil in place of thymine, which is in DNA)

In eukaryal cells, what does RNA polymerase II transcribe?

mRNA genes

In yeast DNA replication starts by specific proteins binding at the autonomously replicating sequence (ARS). Where does replication start in bacteria?

the oriC

Suppose a microbe has died and lysed, exposing its DNA to the environment. Some of this DNA was taken up by another unrelated microbe and incorporated into its genome. This is an example of which process?

horizontal gene transfer

Term for the uptake of extracellular DNA into a bacterial cell and incorporation into its genome

transformation

You are searching for a mutant strain of Salmonella enterica which is antibiotic sensitive. Which method would you employ to find such a mutant?

Replica plating

The ______ protein is important in the process of recombination

RecA

What is metagenomics?

A culture-independent method that may be used to document microbial community pools of genetic material

The sequencing method which uses detection of pyrophosphate liberated when nucleotides are added to a growing DNA chain is called:

Pyrosequencing

What is a transcriptome?

The transcripts encoded for by the genes within a genome

You are analyzing a ~20,000 bp long DNA fragment that is part of a metagenome.

Based on your experience in identifying microorganisms, what gene would you look for to best identify the organism that the DNA fragment might have come from?

16S rRNA gene

Term for genes from different organisms that encode for proteins that carry out the same function but have different sequences.

orthologs

The main differences between Bacteria and Archaea chromosomal DNA when compared to Eukarya chromosomal DNA, is that the Bacteria or Archaea chromosome usually:

is circular while Eukarya is linear

The Watson and Crick model showed that in the DNA molecule:

purines paired with pyrimidines, and the strands align anti-parallel to one another

What does Rho-independent termination of transcription in bacteria involve?

The formation of a hairpin loop followed by a poly U sequence

Term for cells that can naturally take up extracellular DNA

competent

What is the isoelectric point of a protein?

the pH at which a protein has no net charge

DNA microarray analysis may be used to study:

gene expression in cells grown under different conditions

What is the "sexual transfer" of genes in bacteria called?

conjugation

What is the first protein to bind to the oriC region of the DNA molecule to start the replication process?

DnaA

Replication of the bacterial chromosome begins at how many locations?

one

Term for a special sequence at the end of the chromosome in eukaryal cells

telomere

You insert a gene for tetracycline resistance into one plasmid and a gene for ampicillin resistance into another plasmid. You successfully introduce both plasmids into a sample of E. coli cells, but the E. coli cells do not grow in culture medium with both antibiotics present in it. What could best explain the problem?

Plasmid incompatibility will not allow both plasmids to persist

What did the experiment by Fred Griffith in 1928 with the R and S strains of Streptococcus pneumoniae demonstrate?

genetic material from one strain could be transferred to another strain.

The DNA replication process in Archaea more closely resembles that in:

Eukarya

Most bacterial promoters consists of two regions:

Pribnow (TATA) box and -35 region

What is an organism's complete collection of alleles called?

genotype

Which of these is TRUE regarding horizontal gene transfer?

it occurs commonly in nature

Suppose it is observed that a small section of a microorganism's chromosome varies significantly in GC content from the majority of the chromosome. What likely caused this?

horizontal gene transfer

Genes which confer invasiveness to a pathogen and whose GC content varies significantly from that of the total genome constitute:

pathogenicity islands

Initiation of translation in bacteria starts with the binding of the ribosome to the mRNA molecule. The ribosomal binding site is nearer the 5' end of the mRNA molecule and is called the ________.

Shine-Dalgarno sequence

After the translational process the polypeptide folds into the appropriate conformation for proper functioning. What group of proteins aids in protein folding?

chaperonins

You are receiving a bacterial strain from the American Type and Culture Collection. The strain is labeled E. coli K12 Leu- Pro-. What does this mean?

the strain is a mutant incapable of leucine and proline synthesis

Suppose a mutant strain of Escherichia coli K12 contains a mutation in the trpE gene and is no longer able to make tryptophan. What is this mutant called?

An auxotroph

Bacillus anthracis, B. cereus and B. thuringiensis are three very closely related species of the same genus. If the genes that distinguish these three species from one another were are all plasmid-encoded, it might be more correct to consider them as:

Strains of a single species

The Sanger method of sequencing uses ALL of the following EXCEPT:

restriction enzymes

Why is it difficult to define "species" accurately when considering bacterial life forms?

All are correct choices:

(Genome sizes vary considerable. + Novel genes are found in some species members. + Mutation is ongoing and complicates sequence comparisons.+ Bacteria do not reproduce sexually)

What did the experiment by Avery, MacLeod, and McCarty in 1944 with the R and S strains of Streptococcus pneumoniae demonstrate?

DNA was the genetic material in cells

Bacteriophages vary in their ability to infect different strains of bacteria. This is because some bacteria contain ________ _______ that cut the phage DNA after it enters the cell

Restriction endonucleases

What is a wild-type strain?

An original strain isolated from any environment before introduction of mutations

You are searching for a mutant strain of Serratia marcescens which produces no pigment. What approach is most likely to be successful?

Replica plating

Which of these is another term for the Sanger method of DNA sequencing?

dideoxy sequencing

What is a proteome?

The translated products encoded for by the genes within a genome

Two-dimensional polyacrylamide gel electrophoreses (2D-PAGE) separates proteins based on what property or properties?

Size and charge

What are micro RNAs?

small regulatory RNAs

Which of these results from a deletion of base pairs such that the amino acid sequence is disrupted from that point downward?

frameshift mutation

You are searching for a mutant strain of E. coli which is antibiotic resistant. What approach is most likely to be successful?

Replica plating on selective and non-selective media

Which term applies to the transfer of genes from mother to daughter cell?

vertical gene transfer

Bacterial mutants have been very useful for studying and understanding:

all of these choices

carbon metabolism

antibiotic resistance

capsule production

biosynthetic pathways

all of these choices

What is an open-reading frame?

The protein encoding sequence of a gene

what is a codon?

Three bases on the mRNA that is read by the ribosome in the 5' to 3' direction

The Hershey and Chase experiment was able to conclusively demonstrate that DNA, not protein, was the genetic material. They were able to distinguish DNA from protein since labelled ________ incorporated into DNA while labelled _______ incorporated into protiens.

phosphorus; sulfur

Which of these would a signal peptide be used for in bacteria?

To move a protein to the outside of the cell

Under what conditions will two different plasmids be incompatible?

If they use similar methods of replication initiation (ori)

Which of the enzymes is not required for homologous recombination to occur?

DNA polymerase

What are paralogs?

Genes that arise from a duplication event in an organism

Term for the transfer of donor DNA to a recipient bacterium via a bacteriophage

Transduction

Which enzyme removes the RNA primer and fills in the gap during DNA replication in bacteria?

DNA polymerase I

Which enzyme is responsible for adding the final bases to the end of a chromosome during DNA replication in eukaryal cells?

telomerase

What is considered a bacterial strain's genome:

chromosome, plasmids, and lysogenic phage DNA

Genetic elements that are able to "jump" around on the chromosome

transposons

Which of these is a term for a point mutation that results in a change in the amino acid specificity of the codon and the synthesized polypeptide?

Missense

How do nucleotides connect to adjacent nucleotides in the Watson-Crick model of DNA?

Via a covalent bond between the 3' hydroxyl of one nucleotide and the 5' phosphate of the other.

Replication termination in E. coli involves which two proteins?

Tus protein and topoisomerase II

Escherichia coli strain K12 is considered a wild-type strain and does not have any nutritional vitamin requirements. What term applies to this strain?

A prototroph

The most commonly observed promoter sequence seen in an organism is known as the:

Consensus sequence

The term for a large group of genes whose expression is under the control of a single regulatory system

regulon

What is diauxic growth?

Sequential use of different carbon sources leading to different growth rates

Translated types of RNA include:

mRNA

Which autoinducer is used by many Gram-negative bacteria?

a type of homoserine lactone

During negative regulation of gene expression the repressor protein binds to the operator to inhibit transcription. What is the effector molecule that controls the activity of the repressor protein called?

corepressor or inducer

Which component of the two-component regulatory system frequently senses changes in the external environment?

histidine kinase

How is chemotaxis regulated?

By a series of signal transduction events

How will E. coli growing in a medium containing both lactose and glucose react?

By preferentially utilizing glucose first

Once the autoinducer excreted by Vibrio fischeri reaches a critical concentration, it is able to diffuse back into the cell. What is its next action?

Bind to a transcriptional activator protein to activate transcription of the lux genes

Which of these is typically involved in a two-component regulatory system?

Histidine kinase and a response regulator

When does repression of the lac operon occur?

When the repressor protein binds to the operator region

What precisely does messenger RNA (mRNA) encode?

amino acid sequence of a polypeptide

A gene can best be described as a segment of DNA that:

is transcribed into RNA, plus the associated DNA region necessary for transcription

A vector with a genome consisting of the cos site derived from phage lambda flanked by approximately 35-45 kb exogenous DNA would be known as a:

cosmid vector

A bacterium that can synthesize all organic molecules needed for its growth from one carbon molecule, e.g. glucose, is known as a/an:

prototroph

What is the Sigma factor of the RNA polymerase Holoenzyme responsible for?

Recognition of the promoter region.

3 MULTIPLE CHOICE OPTIONS

Which of these enzymes is not required for homologous recombination to occur?

DNA Polymerase

Initiation of translation in bacteria starts with the binding of the ribosomes to the mRNA molecule. The MRNA binds with its ________to the 3' end of the ________.

Shine- Dalgarno sequence; 16s rRNA

Which statement below is FALSE regarding replication of the bacterial chromosome?

The leading strand is replicated in the 5' to 3' direction and the lagging strand in the 3' to 5' direction

Which of these is required for transcription that is regulated by positive control?

activator protein

What is an effector molecule?

A small molecule that binds to an enzyme/protein to regulate its activity

How is quorum sensing, a type of cell to cell communication, mediated?

By chemical signaling

What does sigma factor helps the RNA polymerase do?

Identify the promoter region of a gene

Small non-coding RNA molecules (sRNA) affect gene expression at the level of:

Transcription elongation

Post-initiation control of gene expression can be accomplished by:

small RNAs

Which of the following is not an example of a regulon?

lac operon

When glucose and lactose are present, which substrate is used by microbes:

Lactose metabolism is repressed until glucose is used up

The genome size of Archaea is?

In the same range as in Bacteria

In bacterial cells mRNA can be polycistronic. What does this mean?

It contains the code for multiple peptides

Bacterial mutants have been very useful for studying and understanding:

All of the choices

In bacteria the replication of the chromosome is initiated by binding of which protein to the origin of replication?

DnaA

Which of these controls the expression of the lac operon?

Both repression and activation mechanisms