Bacterial Conjugation Practice Problems

Suppose you want to study the transfer of a plasmid containing a gene for ampicillin resistance from a donor strain to a recipient strain. Unlike the donor strain which is resistant to ampicillin, the recipient strain is sensitive to ampicillin and lacked the plasmid.

To test the transfer of the plasmid, you perform an interrupted mating experiment where samples are taken at various time intervals and plated on a selective medium containing ampicillin to identify transconjugants.

What will you expect from the number of transconjugants over time provided that the transfer of the plasmid is successful?

In a bacterial conjugation experiment, a researcher wanted to study the transfer of a plasmid containing a gene for resistance to streptomycin from a donor strain to a recipient strain. The donor strain was resistant to streptomycin and carried the plasmid, while the recipient strain was sensitive to streptomycin and lacked the plasmid.

The researcher interrupted the mating at different time intervals and plated the conjugation mixture on a selective medium containing streptomycin to identify the transconjugants. The researcher obtained the following data:

Time (minutes)   Number of transconjugant colonies
     0                              0
   10                            20
   20                           100
   30                           300
   40                           400

What is the transfer rate between 20 and 30 minutes?

In an experiment, a researcher wanted to test the transfer of a plasmid containing a gene for resistance to streptomycin from a donor strain to a recipient strain through bacterial conjugation. The donor strain was resistant to streptomycin and carried the plasmid, while the recipient strain was sensitive to streptomycin and lacked the plasmid. 

The researcher used a selective medium that contained streptomycin to identify the transconjugants after the conjugation. After incubation, the researcher observed the growth of colonies on the selective medium. The results showed the presence of transconjugant colonies on the selective medium. The transfer of the resistant gene is then tested through PCR. 

What results would the researcher expect to see if the resistance gene was successfully transferred to the recipient strain?

In a bacterial conjugation experiment, a researcher wanted to investigate the transfer of a plasmid containing a resistance gene from a donor strain to a recipient strain. The donor strain was resistant to ampicillin and carried the plasmid, while the recipient strain was sensitive to ampicillin and lacked the plasmid. The researcher used a selective medium that contained ampicillin to identify the transconjugants after the conjugation.

After incubation, the researcher observed the growth of colonies on the selective medium. The results showed the presence of transconjugant colonies on the selective medium. The researcher then picked ten random transconjugant colonies and tested them for ampicillin resistance. Nine of the colonies were resistant to ampicillin, while one colony was sensitive to ampicillin.

What conclusion can the researcher make about the transfer of the plasmid and the resistance gene from the donor strain to the recipient strain?

The F plasmid contains two main loci and two other regions that help prevent the transferring of the F plasmid to an F⁺ cell. These loci include tra and trb locus and the other two regions are the origin of replication (OriV) and the origin of transfer (OriT). Which region or locus codes for proteins that form the pili?

In an experiment on bacterial conjugation, a researcher observed that the F-plasmid transfer from the donor to the recipient strain takes place at a constant rate. The researcher measured the number of minutes it took for each of the first six genes on the plasmid to be transferred to the recipient strain. The results are shown in the table below:

How long does it take for each gene to be transferred?

In an experiment, two different bacterial strains were used: Strain A is arg⁻ pro⁺ and Strain B is arg⁺ pro⁻. When the two strains were mixed in a culture medium lacking arginine and proline, no growth was observed. However, when a small amount of arginine and proline was added to the medium, growth was observed. A third strain, C, was also used in the experiment, which was arg⁻ pro⁻.

Based on these results, which of the following statements is therefore true?

In an experiment, two different bacterial strains are studied for their ability to synthesize the amino acid tryptophan. Strain A is trp⁺ his⁻ and Strain B is trp⁻ his⁺. When the two strains are mixed in a culture medium lacking tryptophan, no growth is observed. However, when a small amount of tryptophan is added to the medium, growth is observed. What is illustrated from this experiment?

An interrupted mating experiment is used to study the distance between genes on a chromosome. In this experiment, conjugation between an Hfr strain and an F- strain is interrupted at specific time intervals, and the resulting cells are plated onto selective media. The phenotype of the resulting colonies is used to determine the order and distance of the genes on the chromosome.

In an experiment involving three different Hfr strains, the following data were obtained:

Hfr strain 1       oriT gene A gene B gene C
Duration (min)    0        2         7         10
Hfr strain 2       oriT gene A gene C gene B
Duration (min)    0        2         8          12
Hfr strain 3       oriT gene C gene B gene A
Duration (min)    0        3         8          15

What is the order of the genes on the chromosome in the donor strain?

Which of the following genes is located nearest to the leading side of the F factor if an F- bacterial strain with genotypes lac-, arg+, his-, met- is mated with an Hfr bacterial strain with genotypes lac+, arg-, his+, met+ and the time taken to transfer the donor genes is lac 10 minutes, arg 6 minutes, his 3 minutes, and met 12 minutes? 

Which of the following statements regarding interrupted mating experiment in conjugation is true?

To determine the order of the genes on the chromosome, an interrupted mating study is carried out between the Hfr donor strain, leu+ pro+ trp+ his+, and the recipient, leu- pro- trp- his-. After conjugation is established, a small sample of the mixture is collected every minute for 20 minutes and the results obtained are as follows: Leu - 8 minutes, trp - 17 minutes, his - 12 minutes, and pro - 0 minutes. Which of the following is the correct order of sequence?

The conjugation process is utilized in interrupted mating experiments to map the bacterial chromosome's gene order. What is the advantage of using a selective medium in an interrupted mating experiment?

Interrupted mating experiments can be used to determine the order of markers entering a recipient cell for any Hfr strain. What is the order of markers in the F+ strain if the following data is obtained from several Hfr strains derived from the same F+?
Hfr strain 1 —R–H–E–Z→
Hfr strain 2 —K–O–S–Z→
Hfr strain 3 —O–K–W–I→
Hfr strain 4 —R–T–I–W→
Hfr strain 5 —H–R–T–I

What is the order of the genes in a cross between an Hfr H of genotype Lac+, proC+, his+, and an F- strain negative for all these genes, if the mixture is plated out on a medium containing histidine as the sole carbon source and the pattern is His+ - 100%, Lac+ - 40%, proC+ - 50%?

E.coli is used in an experiment to determine the order of genes. A cross was made between Hfr H of genotype Lac+, proC+, gal+, and an F- strain negative for all these genes. After about 2 hours, the mixture was diluted and plated out on a medium containing galactose as the sole carbon source and got the pattern: Gal+ - 100%, Lac+ 30%, proC+ - 45%. Determine the order of the genes.

Which of the following statements about conjugation and transformation is true?

________ is an oligomeric protein that forms fimbriae and pili, which are extensions of the cytoplasmic membrane.

a. relaxosome

b. glycoprotein

c. pilin

d. keratin

The T-strand of the plasmid contains _______ which is recognized by the relaxase enzyme.

Which of the following enzymes binds the origin of transfer (oriT) of the plasmid's T-strand and cleaves the strand at the nic site, allowing for the transfer of genetic material from the donor to recipient bacteria?

Which of the following is a complex of proteins that creates a nick in the plasmid allowing for the transfer of DNA from one organism to another?

Through _______________________ process, a harmless bacterium directly receives and incorporates the DNA material into its chromosome from a pathogenic bacterium via horizontal gene transfer and too may become pathogenic.

The process by which one bacterium transfers genetic material to another via direct contact is known as conjugation. With the help of the _________, contact is made between the two cells.

Which of the following statements regarding conjugative plasmids is incorrect?

Which of the following statements regarding conjugation frequency is true?

Conjugation is usually measured in terms of conjugation frequency per donor or recipient. Conjugation frequency is calculated as:

Which of the following features of R plasmid is incorrect? 

When it comes to the conjugation of an Hfr bacterium and an F- bacterium, which of the following statements is not true?

In an interrupted mating experiment between the donor and the recipient bacteria, we can determine:

What would be the order of the genes that start with E from the following list of genes that show the results of interrupted-mating experiments with three different Hfr stains?

HFR strain 1 - D, E, B, A, G; HFR strain 2 - A, B, E, D, F; HFR strain 3 - D, F, C, G, A

The F⁻ strain, called the recipient appears to have the tonR gene after 12 minutes, the aziR gene after 18 minutes, and the his+ gene after 14 minutes from an Hfr strain in an interrupted mating experiment; however, the recipient almost never has lac+. Where in the genome is the origin of transfer?

By using the process of conjugation to map the order of genes on a bacterial chromosome, an F- bacterial strain with genotypes gal-, leu-, cys-, thr- was used alongside an Hfr bacterial strain with genotypes gal+, leu+, cys+, thr+. The mating was stopped regularly, and the time taken to transfer the donor genes was: gal 10 minutes, thr 6 minutes, cys 3 minutes, and leu 12 minutes. Which gene is located farthest to the leading side of the F factor, which is where transfer originates?

To map the bacterial chromosome in a single interrupted mating experiment, which of the following characteristics is necessary?

Lederberg demonstrated the transduction phenomenon, in which genetic information is transferred from one bacterium to another through one of the following processes:

By combining _____ and ______ cells of different genotypes, conjugation can be used to map bacterial genes.

Which of the following structures mediates the physical interaction during conjugation?

Which of the following best describes the outcome of an F− cell when HFR binds to an F− bacterium?

By initiating conjugation, _______ bacteria can transfer the genetic material that is embedded in its chromosomal DNA.

The process of conjugation does not occur between

________ is the sex factor in bacteria.

Which of the following statements is true concerning bacterial conjugation?

Which of the following statements is false regarding the significance of bacterial conjugation?