Microbial Genetics Practice Questions

Q: The following image shows:

Transformation. ***Transformation*** - The image depicts **Griffith's experiment**, where heat-killed encapsulated bacteria (virulent) are mixed with living non-encapsulated bacteria (non-virulent). - The result (mouse died) indicates that genetic material from the dead virulent bacteria was **taken up by the living non-virulent bacteria**, transforming them into virulent forms. *Transduction* - **Transduction** involves the transfer of genetic material from one bacterium to another via a **bacteriophage (virus)**. - The experiment shown does not involve phages or viral mediation in genetic transfer. *Lysogenic conversion* - **Lysogenic conversion** is a specific type of transduction where a bacterium acquires new traits due to the presence of a **temperate bacteriophage** (prophage) integrated into its genome. - While related to phages, it's not the general mechanism depicted where bacterial DNA is directly acquired from the environment. *Conjugation* - **Conjugation** is the transfer of genetic material between bacteria through direct cell-to-cell contact, typically via a **pilus**. - No direct contact or pilus formation is shown in the experimental setup; instead, genetic material is absorbed from the environment.

Q: The following image shows:

Transduction. ***Transduction*** - The image illustrates a **bacteriophage** injecting its DNA into a donor bacterial cell, leading to the packaging of bacterial DNA into new phage particles. - Subsequently, these phages infect a recipient cell, transferring the **donor bacterial DNA** and indicating genetic transfer mediated by a virus. *Transformation* - This process involves the direct uptake of **naked extracellular DNA** by competent bacterial cells. - The image clearly depicts a **phage (virus)** mediating the transfer, not naked DNA uptake. *Lysogenic conversion* - This occurs when a bacterium acquires new characteristics due to the presence of a **prophage (integrated bacteriophage DNA)**, which does not necessarily involve general transfer of host DNA to another bacterium. - The image shows the transfer of bacterial DNA from one bacterium to another via a phage, rather than a change in phenotype due to prophage integration. *Conjugation* - This is the direct transfer of genetic material between bacterial cells through cell-to-cell contact, typically via a **pilus**. - The image shows a **phage** as the vector for DNA transfer, not direct bacterial contact.

Q: DNA transfer in bacteria by phage is:

Transduction. ***Transduction*** - **Transduction** is the process by which foreign DNA is introduced into a cell by a virus or viral vector, specifically a **bacteriophage** in bacteria. - During transduction, the phage infects a bacterial cell, and its genetic material becomes incorporated into the host cell's DNA, or it may package bacterial DNA into new phage particles, which then infect other bacteria. *Transformation* - **Transformation** is the process where bacteria take up **naked DNA** from their environment. - This process does not involve a bacteriophage or any other viral vector. *Conjugation* - **Conjugation** is a process of genetic transfer between bacterial cells involving direct cell-to-cell contact through a **pilus**. - It typically involves the transfer of plasmids or other genetic elements, not mediated by a bacteriophage. *Translation* - **Translation** is the process by which messenger RNA (mRNA) is decoded to produce a specific **amino acid sequence** (protein). - This is a fundamental step in gene expression and does not involve the transfer of DNA between bacteria via a phage.

Q: What is the mode of transmission of genetic material to bacteria through bacteriophage?

Transduction. ***Transduction*** - **Transduction** is the process by which foreign DNA is introduced into a bacterium by a **bacteriophage** (a virus that infects bacteria). - This occurs when a bacteriophage carries bacterial DNA from one bacterium to another, often as a result of errors during viral replication. *Transformation* - **Transformation** involves the uptake of **naked DNA** from the environment by a bacterial cell. - This process does not involve a bacteriophage as an intermediary for genetic transfer. *Conjugation* - **Conjugation** is the transfer of genetic material between bacterial cells by direct cell-to-cell contact through a **pilus**. - This process requires physical contact between two bacteria and does not involve bacteriophages. *Translation* - **Translation** is the process by which messenger RNA (mRNA) is decoded to produce a specific protein. - This is a fundamental step in gene expression and is distinctly different from genetic material transmission between organisms.

Q: Which statement concerning plasmids is true?

R plasmids carry genes for antibiotic resistance. ***R plasmids carry genes for antibiotic resistance*** - **R plasmids** are extrachromosomal DNA molecules found in bacteria that commonly encode **resistance genes** against various antibiotics. - This genetic information allows bacteria to survive in the presence of antibiotics, contributing to issues like multi-drug resistance. *All plasmids possess the information for their own transfer by conjugation* - Only **conjugative plasmids** contain the necessary genes (**tra genes**) to mediate their own transfer between bacteria via conjugation. - **Non-conjugative plasmids** require the presence of a conjugative plasmid in the same cell to be co-transferred. *R plasmids cannot be transferred to other bacterial cells* - Many **R plasmids are conjugative**, meaning they can be readily transferred between bacterial cells, even across different species, via conjugation. - This transfer mechanism is a significant factor in the rapid spread of **antibiotic resistance** in bacterial populations. *Much of the information coded in the plasmid is essential to the survival of the bacteria cell* - Plasmids typically carry genes that provide **selective advantages** under specific conditions (e.g., antibiotic resistance, virulence factors), but these are generally **not essential** for basic cell survival and growth in routine environments. - The essential genes for bacterial survival are located on the **bacterial chromosome**.

Q: False regarding bacterial plasmids is:

Can cause lysogenic conversion. ***Can cause lysogenic conversion*** - **Lysogenic conversion** is a phenomenon caused by **bacteriophages**, which are viruses that infect bacteria, not by plasmids directly. - It involves the integration of a **phage genome** into the bacterial chromosome, altering the bacterium's phenotype (e.g., toxin production). *Extrachromosomal* - Bacterial plasmids are indeed **extrachromosomal DNA molecules**, meaning they exist independently of the bacterial chromosome. - This characteristic allows them to be easily transferred between bacteria. *Transmission of different species* - Plasmids can be transmitted horizontally between bacteria, even across **different species**, through mechanisms like **conjugation**, **transformation**, or **transduction**. - This interspecies transmission is a major factor in the spread of **antibiotic resistance**. *Eliminated by treating with radiation* - Plasmids, like all DNA, can be eliminated or degraded by treatments such as **radiation** (e.g., UV) or certain chemicals. - Such treatments disrupt the plasmid DNA structure, preventing its replication or function.

Q: F factor integrates with bacterial chromosome to form -

Hfr. ***Hfr*** - When the **F plasmid (fertility factor)** integrates into the bacterial chromosome, it forms a **high-frequency recombination (Hfr) strain**. - This integration allows for the transfer of chromosomal DNA during **conjugation**. *F-* - An **F- bacterium** is a recipient cell that **lacks the F plasmid** entirely. - It cannot initiate conjugation as a donor and receives genetic material from F+ or Hfr cells. *F'* - An **F' plasmid** is a variation of the F plasmid that has excised from the bacterial chromosome, carrying with it a **small segment of bacterial chromosomal DNA**. - It differs from simple F plasmids by containing host genes. *F* - The **F factor (fertility factor)** is a type of plasmid that carries genes for pilus formation and DNA transfer. - An F+ bacterium contains this plasmid as an **extrachromosomal element**, but it is not integrated into the chromosome.

Q: The mechanism of direct transfer of free DNA involves _____

Transformation. ***Transformation*** - **Transformation** is a process of horizontal gene transfer where bacteria take up **free DNA** from their environment. - This DNA can originate from dead bacterial cells and be integrated into the recipient bacterium's genome. *Mutation* - A **mutation** is a spontaneous change in the nucleotide sequence of an organism's genome. - It does not involve the transfer of DNA from one organism to another, but rather an alteration within an existing gene. *Conjugation* - **Conjugation** involves the direct transfer of genetic material between bacterial cells through physical contact via a **pilus**. - This mechanism typically transfers large pieces of DNA, often plasmids, not "free DNA" from the environment. *Transduction* - **Transduction** is the process by which DNA is transferred from one bacterium to another by a **bacteriophage** (a virus that infects bacteria). - This mechanism requires a viral vector to carry the genetic material, distinguishing it from the direct uptake of free DNA.

Q: Which of the following organisms is a natural transformer?

Neisseria gonorrhoeae. ***Neisseria gonorrhoeae*** - *Neisseria gonorrhoeae* is known as a **natural transformer** because it can actively take up exogenous DNA from its environment. - This capability is significant for its **genetic variability** and antibiotic resistance development through horizontal gene transfer. *Escherichia coli* - *E. coli* is not naturally competent; it requires **artificial methods** such as heat shock or electroporation to take up foreign DNA in laboratories. - While widely used in genetic engineering, its transformation is not a **natural physiological process**. *Plasmodium vivax* - *Plasmodium vivax* is a **eukaryotic parasite** responsible for malaria, and it does not undergo bacterial transformation. - Its genetic exchange mechanisms are complex and involve **sexual reproduction** within the mosquito vector, not direct DNA uptake from the environment. *Pseudomonas aeruginosa* - *Pseudomonas aeruginosa* is a bacterium that can exhibit some level of natural competence, but it is not as highly recognized for it as *Neisseria* species. - Its ability to take up DNA is often **inducible** and less constitutive compared to primary natural transformers.

Q: All the following terms are used to describe bacterial chromosome Except

Diploid. ***Diploid*** - Bacterial chromosomes are typically **haploid**, meaning they contain only one copy of each gene, not two sets as in diploid organisms. - While bacteria can sometimes have multiple copies of their chromosome, these copies are usually identical replicas and do not represent distinct sets of genetic information. *Circular* - The bacterial chromosome is characteristically a **single, closed circular DNA molecule**. - This circular structure distinguishes bacterial chromosomes from the linear chromosomes found in eukaryotes. *Nucleoid* - The bacterial chromosome is located in a region of the cytoplasm called the **nucleoid**, as bacteria lack a membrane-bound nucleus. - The nucleoid is where the genetic material is condensed and organized within the bacterial cell. *Haploid* - Bacteria are essentially **haploid organisms**, possessing a single set of chromosomes. - This means they have only one allele for each gene, which can lead to rapid expression of mutations.

Question 1

The following image shows:

Accepted Answer

Transformation

Answer

Transduction

Answer

Lysogenic conversion

Answer

Conjugation

Question 2

The following image shows:

Accepted Answer

Transduction

Answer

Transformation

Answer

Lysogenic conversion

Answer

Conjugation

Question 3

DNA transfer in bacteria by phage is:

Accepted Answer

Transduction

Answer

Transformation

Answer

Conjugation

Answer

Translation

Question 4

What is the mode of transmission of genetic material to bacteria through bacteriophage?

Accepted Answer

Transduction

Answer

Transformation

Answer

Conjugation

Answer

Translation

Question 5

Which statement concerning plasmids is true?

Accepted Answer

R plasmids carry genes for antibiotic resistance

Answer

All plasmids possess the information for their own transfer by conjugation

Answer

R plasmids cannot be transferred to other bacterial cells

Answer

Much of the information coded in the plasmid is essential to the survival of the bacteria cell

Question 6

False regarding bacterial plasmids is:

Accepted Answer

Can cause lysogenic conversion

Answer

Extrachromosomal

Answer

Transmission to different species

Answer

Eliminated by treating with radiation

Question 7

F factor integrates with bacterial chromosome to form -

Accepted Answer

Hfr

Answer

F-

Answer

F'

Answer

F

Question 8

The mechanism of direct transfer of free DNA involves _____

Accepted Answer

Transformation

Answer

Mutation

Answer

Conjugation

Answer

Transduction

Question 9

Which of the following organisms is a natural transformer?

Accepted Answer

Neisseria gonorrhoeae

Answer

Escherichia coli

Answer

Plasmodium vivax

Answer

Pseudomonas aeruginosa

Question 10

All the following terms are used to describe bacterial chromosome Except

Accepted Answer

Diploid

Answer

Circular

Answer

Nucleoid

Answer

Haploid

Microbial Genetics — MCQs

Microbial Genetics — MCQs

On this page

Practice by Chapter

Want unlimited practice?