Microbial Genetics Practice Questions

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.

Q: Transfer of a portion of DNA from one bacterium to another by bacteriophage is known as

Transduction. ***Transduction*** - **Transduction** is a process where bacterial DNA is transferred from one bacterium to another via a **bacteriophage** (a virus that infects bacteria). - The bacteriophage accidentally packages bacterial DNA instead of its own genetic material and then injects it into a new host bacterium. - This is the defining mechanism that distinguishes transduction from other forms of horizontal gene transfer. *Conjugation* - **Conjugation** involves the direct transfer of genetic material (usually plasmids) between bacterial cells through physical contact, often via a **pilus**. - It does not involve a bacteriophage as an intermediary for DNA transfer. *Transformation* - **Transformation** is the process by which bacteria take up **free DNA** from their environment. - This DNA can come from lysed bacterial cells and does not involve bacteriophages. *Mutation* - A **mutation** is a change in the DNA sequence of an organism. - While it alters genetic material, it is not a mechanism for the transfer of DNA between bacteria.

Question 1

The following image shows:

Accepted Answer

Transduction

Answer

Transformation

Answer

Lysogenic conversion

Answer

Conjugation

Question 2

DNA transfer in bacteria by phage is:

Accepted Answer

Transduction

Answer

Transformation

Answer

Conjugation

Answer

Translation

Question 3

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

Accepted Answer

Transduction

Answer

Transformation

Answer

Conjugation

Answer

Translation

Question 4

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 5

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 6

F factor integrates with bacterial chromosome to form -

Accepted Answer

Hfr

Answer

F-

Answer

F'

Answer

F

Question 7

The mechanism of direct transfer of free DNA involves _____

Accepted Answer

Transformation

Answer

Mutation

Answer

Conjugation

Answer

Transduction

Question 8

Which of the following organisms is a natural transformer?

Accepted Answer

Neisseria gonorrhoeae

Answer

Escherichia coli

Answer

Plasmodium vivax

Answer

Pseudomonas aeruginosa

Question 9

All the following terms are used to describe bacterial chromosome Except

Accepted Answer

Diploid

Answer

Circular

Answer

Nucleoid

Answer

Haploid

Question 10

Transfer of a portion of DNA from one bacterium to another by bacteriophage is known as

Accepted Answer

Transduction

Answer

Conjugation

Answer

Transformation

Answer

Mutation

Microbial Genetics — MCQs

Microbial Genetics — MCQs

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