Genetics Exam 4

Which of the following is FALSE regarding regulation of gene expression in bacteria?

Regulated transcription is necessary; constitutive transcription, continuously transcribing genes with no regulatory control, does not occur without mutation.

Which of the following mutants are noninducible?

lacIS

Which part of the lac operon is cis-dominant?

lacO

Which of these haploid strains produces permease inducibly, but does not produce β-galactosidase?

I+ P+ O+ Z — Y+

In a partial diploid of the genotype I— P+ O+ Z— Y+/ I+ P— O+ Z+ Y+, synthesis of

β-galactosidase will be uninducible and permease will be inducible

Which of the following best describes expression of the lac genes in this partial diploid? I+ P+OC Z– Y+/ I– P+ O+ Z+ Y–

β-galactosidase is only made when lactose is present, but permease is made both in the presence and absence of lactose.

During the attenuation of the trp operon, which stem loop leads to polycistronic mRNA synthesis during tryptophan starvation?

2-3 (antitermination) stem loop

) Disrupting the formation of which stem-loop structure of trpL would decrease the efficiency of transcriptional regulation?

3-4 (termination) stem loop

Which of the following statements regarding attenuation of the trp operon is NOT true?

When tryptophan levels are low, the ribosome will occupy regions 1 and 2 after completing translation of the coding sequence, regions 3 and 4 will pair, and transcription will terminate.

Which of the following genotypes and conditions will have the LOWEST level of trp operon expression?

trpP- / tryptophan absent

Which of the following mutations of the trpL region would be least likely to affect attenuation of trp operon transcription?

an insertion of two nucleotides immediately after the polypeptide stop codon

Which of the following is FALSE regarding how bacteria regulate the transcription of stress response genes?

Transcription is activated by antitermination, which allows transcription to extend into heat shock genes.

Which of the following is FALSE regarding translational regulation in bacteria?

It is the most predominant mode of controlling gene expression in bacteria.

Which of the following regarding riboswitches is correct?

They can regulate bacterial transcription, translation, and mRNA stability

You have identified a mutation in a gene that seems to decrease transcription of another gene 2000 bp away from the mutation site. What regulatory sequence, which may be found within another gene, has likely been mutated in this instance?

enhancer sequence

Multicellular organisms generally utilize more complex gene regulation than unicellular organisms via mechanisms that include?

transcriptional repression and epigenetic modification

For the following gene, MspI and HpaII restriction sites and their positions are indicated here. Recall that HpaII is methylation sensitive, while MspI is not.If this gene is being actively transcribed, how many fragments would you expect from this restrictio digest?

C

Which of the following would you expect to show the least evolutionary conservation?

intergenic DNA

Chromatin remodeling involves both sliding and relocating of the nucleosomes. Which eukaryotic chromatin remodeling complex is likely involved?

SWI/SNF complex

Why are filters overlaid with X‑ray film when screening a cDNA library?

To visualize probe hybridization events

(t or f) Chromosome walking is used mainly to isolate a gene when the sequence of the gene is known.

false — chromosome walking is used when the gene of interest has not been cloned yet

   What is the function of restriction endonucleases in bacteria?  

   They provide a defense mechanism against infection by viruses.    — they recognize and degrade viral DNA, thus preventing viral infections

     Restriction endonucleases cut DNA at specific recognition sequences and then bond two strands covalently with the same "sticky ends."  

False — DNA ligase is the one that does the sticking together

Which kind of DNA sequences is one strand of a restriction enzyme recognition sequence?

palindromic sequences

To ensure that a human gene is translated properly in a bacterial cell, you should clone the _____________ for the gene instead of the genomic DNA fragment that contains the gene.

cDNA

Which of the following statements regarding restriction enzymes is NOT true? S

Most restriction enzymes recognize sequences of 20-25 bp in length.        (usually 4-8 bp)

You have a linear DNA fragment of 1600 bp. To characterize it, you decide to make a restriction map. Cutting with one enzyme, you show by electrophoresis that the fragments produced are 400 and 1200 bp. Cutting the same DNA with another enzyme you recover 700 and 900 bp fragments. After treatment with both enzymes, fragments were 300, 400, and 900 bp. Which of the following order of fragments, if any, best represents the restriction map?

400/ 300/ 900

Assume that a plasmid is 4000 base pairs in length and has restriction sites at the following locations: 600, 1000, 2200, and 3800. Give the expected sizes of the restriction fragments following complete digestion.

400 bp, 800 bp, 1200 bp, 1600 bp

If bacteria containing non-recombinant pUC18 are plated on X-gal medium, would colonies appear blue or white or both?

blue

Efficient production of eukaryotic proteins in E. coli may require all of the following except?

a negative selectable marker to select against nonhomologous recombination events

Which of the following is true of the sequences found in DNA libraries from human tissues?

Those in a muscle cDNA library should all be present in a brain genomic library.

If bacteria transformed with a recombinant pUC18 plasmid produce white colonies when grown on plates containing ampicillin and Xgal, which of the following is least likely?

They produce functional β-galactosidase that cleaves X-gal.

In producing a recombinant plasmid to be used to clone a given donor insert, it is possible to cut both the donor and plasmid with the same restriction enzyme, resulting in complementary sticky ends. Assuming plenty of plasmid DNA is available, why is further selection necessary before the introduction of the plasmid into a cellular system?

Some donor strands will be inserted with an incorrect orientation.

In the pUC plasmids, a polylinker region that includes multiple restriction sites is embedded in the lacZ component. If a sequence of interest is inserted into this region, what is the effect on lacZ?

inactivation

Which type of DNA library (genomic or cDNA) would include introns and promoters?

genomic

What technique of genomic library construction allows the genome to be cut by a given restriction enzyme at some but not all recognition sequences?

partial digestion

In a cDNA library, not all genes will be represented. What does this depend on?

on the tissue the mRNA comes from

   Which of the following components would be required in a bacterial expression vector, but NOT in a bacterial cloning vector?

promoter

 Which of the following sequences is/are essential in a yeast shuttle vector?

 Bacterial and yeast origins of replication        

     Illegitimate recombination (i.e., recombination not based on sequence homology) refers to which of the following processes?

         Integration of introduced DNA at random locations in the host chromosome    

The binary approach uses both a transformation vector that contains the T-region flanked by border sequences and a disarmed ________ with the genes required for virulence and conjugative transfer.

Ti plasmid

Which of the following is true regarding the Cre-lox recombination system?

It can be used to remove selectable markers in transgenic organisms.

Which of the following is FALSE regarding P element-mediated transformation?

The transposase activity inserts P elements into the genome at specific positions in the genome.

Which of the following is FALSE regarding the formation of transgenic animals?

Homologous recombination occurs much more frequency than illegitimate recombination.

Why might the expression of a transgene be especially abnormal in vertebrates with larger average size of genes and amount of heterochromatin in their genomes?

position effect

In using Agrobacterium tumefaciens to transfer genes into plants, what is transferred from bacterium to plant?

T-DNA

If a gene is replaced with a heterologous sequence such that the gene is then nonfunctional, what is the result usually called?

knockout

Agrobacterium tumefaciens is often used in the production of transgenic plants because of its Ti plasmid. This plasmid is usually "disarmed" by deleting its tumor genes along with the genes for producing what products that would have been advantageous to the bacterium?

opines

Suppose a gene from a cow is introduced into a frog. This results in a ________ transgene.

heterologous

Are CRISPR_Cas9 edited organisms considered to be transgenic if exogenous DNA is used?

yes

What do expression vectors contain?

Muti-cloning site (MCS), origin of replication, promoter, selectable marker, shine-dalgarno sequence in 5’ UTR, transcription terminator