mcb3023 exam 2

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

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

To move a protein to the outside of the cell

Which of these is a point mutation that results in changing a codon from an amino acid codon to a stop codon?

nonsense

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

5' end; Shine-Dalgarno sequence

The mRNA of bacterial cells is often polycistronic. What does this term mean?

It contains the code for multiple peptides

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

chaperonins

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

Compared to the eukaryal genome, the bacterial genome:

contains usually one chromosome and most genes occur in a single copy

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

transduction

Under what conditions will two different plasmids be incompatible?

If they use similar methods of replication initiation (ori)

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

What sized fragments will be generated by cutting DNA with a four base pair-recognition restriction endonuclease if we assume equal A-T and C-G richness within the DNA?

roughly 250 bp

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

Pyrosequencing

Which of these is TRUE regarding horizontal gene transfer?

It is always occurring in nature

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

dideoxy sequencing

What are paralogs?

Genes that arise from a duplication event in an organism

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.

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.

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

DnaA

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

For the initiation of transcription in bacteria, RNA polymerase binds to what region on the gene?

promoter

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

Eukarya

What is the sigma factor of the RNA polymerase holoenzyme responsible for?

recognition of the promoter region

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

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

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

transposons

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

DNA polymerase

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

You mix Met+ Pro- Lys-, Met-, Pro- Lys+ and Met- Pro+ Lys- auxotrophic strains of E. coli. After incubation time has passed, you place 1020cells per plate on agar to detect potential prototrophic colonies. How many plates need to be screened if gene transfer takes place only through random mutation?

only one plate would be necessary

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

DNA microarray analysis may be used to study:

gene expression in cells grown under different conditions

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

size and charge

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

DNA Polymerase I

Replication termination in E. coli involves which 2 proteins?

Tus protein and topoisomerase II

Which is considered a bacterial strain's genome?

Chromosome, plasmids, and lysogenic phage DNA

Replication of the bacterial chromosome begins at how many locations?

One

Messenger RNA can best be described as a molecule that contains the code for a:

Polypeptide

What, in bacteria, is analogous to the autonomously replicating sequence (ARS) in yeast?

The oriC

Most bacterial promoters consist of two regions _____ and _______.

Pribnow (TATA) box and - 35 region

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

Conjugation

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 the mutant called?

An auxotroph

Bacterial mutants have been very useful for studying and understanding

Carbon metabolism
Capsule production
Antibiotic resistance
Biosynthetic pathways

All of these choices

Term for the direct transfer of DNA from a living donor bacterium to a recipient bacterium

Conjugation

Which of these bacteria will likely take up double stranded DNA during transformation?

Escherichia coli

What is a transcriptome?

The transcripts encoded for by the genes within a genome

You are analyzing a ~20,000 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?

SSU rRNA gene

What is metagenomics?

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

Translated types of RNA include:

mRNA

A repressor protein binds to:

operator

What is diauxic growth?

sequential use of different carbon sources leading to different growth rates

Identify a mechanism that can switch off gene expression

mRNA synthesis inhibition

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

lac operon

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

a telomere

Which of these best differentiates DNA and RNA?

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

All statements are true

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

transformation

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 labeled _____ incorporated into DNA while labeled _____ incorporated into proteins.

phosphorous; sulfur

The process of molecular cloning, i.e. the targeted preparation of DNA fragments for insertion into plasmids requires which of these

restriction enzymes

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

genotype

The ________ protein is important in the process of recombination.

RecA

You are attempting to find a restriction enzyme that will allow a 200 base pair gene fragment to be removed intact from a length of chromosomal DNA. Which enzyme will work best for you?

a six base pair cutter
a four base pair cutter
an eight base pair cutter

all will work equally well

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

restriction enzymes

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 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 is an open-reading frame?

The protein encoding sequence of a gene

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 of these controls the lac operon?

Both repression and activation mechanisms

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

By preferentially utilizing glucose first

Expression of genes that are constitutive is:

Unregulated

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

Histidine kinase

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

Regulon

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

Small RNAs

How are chemotaxis regulated?

By a series of signal transduction events

Identify a mechanism that cannot reduce functional enzyme levels without changes in transcription or translation

Translation inhibition

What is a "reporter gene"?

The fusion of a promoter region of interest to a gene whose product can be easily measured

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

Transcription elongation

The use of sigma factor by RNA polymerase for promoter identification is a type of

Global regulation

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

Shine-Dalgarno sequence, 16S rRNA

In bacteria termination of transcription can be achieved by which mechanisms?

Rho-independent and Rho-dependent

In eukaryal cells, what does RNA polymerase II transcribe?

mRNA genes

The process of molecular cloning was mainly brought about through the discovery of these

restriction enzymes

Term for cells that can naturally take up extracellular DNA

competent

Under what conditions will two different plasmids be incompatible?

If they use similar ori

What is a proteome?

The translational products encoded for by the genes within a genome

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

mutation is ongoing and complicates sequence comparisons
novel genes are found in some species members
genome sizes vary considerable
bacteria do not reproduce sexually

All are correct choices

You are searching for a mutant strain of E.coli with superior heat shock proteins. What approach is most likely to be successful?

DNA seq. of cells within a population

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

Genetic material from one strain could be transferred to another

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

is transcribed as well as the associated regulatory regions

What are the main enzymes responsible for replication of DNA in eukaryal cells?

DNA pol E and S

If the genes that distinguish Bacillus anthracis, B. cereus and B. thuringiensis from one another are all plasmid-encoded, it might be more correct to consider them as:

strains of a single species

Assuming mutation freq. to be around 10^-6, at what frequency will quadruple mutant auxotrophs revert to prototrophy?

1x10^-24

What does Rho-independent termination of transcription in bacteria

formation of a hairpin loop followed by s poly A sequence

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

pathogenicity islands

The Watson and Crick model showed that in DNA molecule

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

You insert a gene for tetracycline resistance into one plasmid and a gene for ampicillin resistance into another plasmid of the same incompatability group. You successfully introduce both plasmids into a sample of E. coli cells, and surprisingly in obtaining growth in culture medium with both antibiotics present in it. What likely happened?

??

Which statement below is FALSE regarding replication of the bacterial chromosome

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

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

DNA seq. of cells within a population

mRNA can be best described as a molecular that contain the code for

protein

What is a codon?

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

What are micro RNAs?

small regulatory RNA's

Suppose a strain of E. coli is identified as an Hfr strain. In a conjugational experiment between the donor Hfr strain and a recipient E. coli strain that is F-, what would you expect to result?

The recipient to remain F-

The strain is labeled Leu-Pro-, what does this mean?

the strain is a mutant incappable of leucine and proline synthesis