RBSE Solutions For Class 12 Biology Chapter 15: Genetic Engineering | Textbook Important Questions & Answers

RBSE Class 12 Biology Chapter 15- Genetic Engineering provides complete information related to genetic engineering, its process, recombinant technology, restriction enzymes, restriction endonuclease, application of enzymes in genetic engineering techniques, plasmids and bacteriophage. It also includes a detailed explanation of recombinant DNA technology, the formation of cDNA library, complementary DNA, genomic library, PCR, RFLP, DNA fingerprinting, blotting techniques and other techniques used for the analysis of cloned genes.

These important questions help students to ace their exams. By practising these important questions, students can analyze their preparation, get a thorough knowledge about all the important terminologies and perform best in their examinations.

The Rajasthan Board Class 12 Solutions are the best study material for both class assignments and other board examinations. By practising these important questions, students can gain deep knowledge about the topics explained in this chapter and also help students to be well prepared for their upcoming examinations.

RBSE Class 12 Biology Chapter 15 Important Questions

RBSE Biology Chapter 15: MCQ Type Questions

Q.1. Restriction Endonuclease.enzyme is found naturally in ______.

(a) Bacteria.

(b) Virus.

(c) Plants.

(d) Animals.

Sol: (a) Bacteria.

Q.2. Which of the following enzymes are used in cutting the DNA at a specific site?

(a) Ligase.

(b) Polymerase.

(c) Restriction Endonuclease.

(d) All of the above.

Sol: (c) Restriction Endonuclease.

Q.3.DNA vector is a ______.

(a) Plasmid.

(b) cDNA.

(c) Synthesized DNA.

(d) All of the above.

Sol: (a) Plasmid.

Q.4. M13 is an example of ______.

(a) Plasmid.

(b) Bacteriophage.

(c) Cosmid.

(d) All of the above.

Sol: (b) Bacteriophage.

Q.5. Which of the following is a source of EcoRI?

(a) Bacteria.

(b) Algae.

(c) Plants.

(d) All of the above.

Sol: (d) All of the above.

Q.6.Which of the following blotting techniques is used in the identification of DNA segments?

(a) Genomic DNA.

(b) Western.

(c) Southern.

(d) Northern.

Sol: (c) Southern.

Q.7. Which enzymes join free DNA ends?

(a) Restriction endonucleases.

(b) Ligases.

(c) Lysozyme.

(d) All of the above.

Sol: (b) Ligases.

Q.8.Jumping genes are called ______.

(a) Phasmid.

(b) Plasmid.

(c) Cosmid.

(d) Transposons.

Sol: (d) Transposons.

Q.9.Which of the following techniques was discovered by Mullis in the year 1989?

(a) Plasmid.

(b) Polymerase chain reaction-PCR.

(c) Southern Blotting technique.

(d) Western Blotting technique.

Sol:(b) Polymerase chain reaction-PCR.

Q.10. C-DNA is used in the formation of ______.

(a) tRNA.

(b) mRNA.

(c) rRNA.

(d) DNA.

Sol: (b) mRNA.

RBSE Biology Chapter 15:Short Answer Type Questions.

Q.1. What is recombinant DNA technology? Who is credited for developing recombinant DNA technology?

Sol: The various effective measures required to incorporate changes in the DNA makeup of any organism is called recombinant DNA technology. Stanley Cohen and Herbert Boyer et al, American geneticists were credited for developing recombinant DNA technology in the year 1973.

Q.2.What are cloning vectors?

Sol: In recombinant DNA technology, in order to introduce the desired gene in the targeted plant or animal a carrier is required which can carry the desired gene and can enter the targeted plant or animal and replicates its DNA. This carrier is called the vector. Plasmid, bacteriophages and Cosmids are used as a vector in recombinant DNA technology.

Q.3. What are marker genes? Give examples of marker genes.

Sol: When the desired genes are incorporated with the vector, several unwanted products are also obtained. In order to eliminate these unwanted products and to identify the recombinant DNA in the host cell, a special type of gene is used. This produces special features in the modified or transformed cells. This gene, which is incorporated in the vector DNA, is called the marker genes. Kanamycin resistant genes are the best example of marker genes.

Q.4. What is meant by molecular probes?

Sol: The segment of DNA or RNA with the help of which C-DNA or RNA segments of some organisms can be identified are called molecular probes. The molecular probes are of the following types. DNA probes and RNA probes.

Q.5. What are marker genes? Give examples of marker genes.

Sol: When the desired gene is incorporated with the vector, several unwanted products are also obtained. In order to eliminate these unwanted products and to identify the recombinant DNA in the host cell, a special type of gene is used. This produces special features in the modified or transformed cells. This gene, which is incorporated in the vector DNA, is called the marker genes. Kanamycin resistant genes are the best example of marker genes.

Q.6. What is the genomic library?

Sol: The collection of the cloned segments of the entire genome of any organism is called the genomic library. A genomic library is formed by taking out the complete DNA content of the haploid set of chromosomes of an organism.

Q.7. What are cosmids?

Sol: Cosmids are a hybrid of plasmids and 2 (ƛ) lambda phages. Such plasmids in which the DNA sequences of Cos site of (ƛ) lambda phages are inserted are known as cosmids.

Q.8. Define the restriction endonuclease enzymes.

Sol: The enzymes which cut the DNA molecules at a specific site are called restriction endonuclease These enzymes function just like molecular scissors, which cut DNA molecules into the segments at a specific site.

Q.9. Name the gels used in gel electrophoresis technique.

Sol: There are two different types of gel, which are used in the process of gel electrophoresis technique. They are – Agarose gel and Polyacrylamide gel.

Q.10. What is a reporter gene? Give examples of the reporter gene.

Sol: There are certain genes, which produce or present some specific features in the host cell. These genes are called the reporter gene. The reporter gene produces a special effect on an account of which the cells containing these genes look different from other cells.

The LUC gene found in fire-fly or Jugnoo and produces bioluminescence is the best example for reporter genes.

Q.11.Define RFLP.

Sol: RFLP stands for Restriction Fragment Length Polymorphism. It is a molecular technique that exploits variations in homologous DNA sequences, in order to distinguish individuals, populations, or species or to pinpoint the locations of genes within a sequence.

Q.12.List out the important achievements of recombinant DNA technology.

Sol: The most important achievements of recombinant DNA technology are:

  1. Human Genome Project.
  2. Cloning of the gene of haemophilia.
  3. Cloning of the hepatitis B virus.
  4. Cloning of nitrogen fixation (Nif) gene.
  5. Cloning of the human growth hormone and insulin gene.
  6. Cloning of penicillin G acylase gene for the production of penicillin

Q.13. What is DNA fingerprinting?

Sol: The method of DNA fingerprinting was first discovered by Alec Jeffreys and his coworkers in the year 1985. DNA fingerprinting is a technique that shows the genetic makeup of living things. It is a method of finding the difference between the satellite DNA regions in the genome.

Q.14.Define PCR – Polymerase Chain Reaction.

Sol: Polymerase Chain Reaction (PCR) is a technique used for creating several copies of a certain DNA segment. This technique was developed in 1983 by Kary Mullis, an American biochemist. PCR has made it possible to generate millions of copies of a small segment of DNA. This tool is commonly used in the molecular biology and biotechnology labs.

Q.15. How is a genomic library formed?

Sol: A genomic library is formed by the isolation of complete DNA of a cell. The different steps involved in the formation of the genomic library are:

The complete genome of a Donor cell
                                                          ↓  Restriction endonuclease enzyme.
DNA fragments Vector DNA
                    ↓ DNA ligase
Circular Recombinant DNA
Insertion into the bacterial cell.
Polymerisation (as a colony).
Identification by DNA Probe.
Formation of Genomic Library.

RBSE Biology Class 12: Long Answer Type Questions

Q.1. What are cloning vectors? Explain how cloning vectors are selected during the process of genetic engineering.

Sol: After the isolation of the desired genes, a vector is required, which can incorporate this gene and along with it, it enters into the host cell and replicates its DNA. This vector is called the cloning vector. Plasmid, bacteriophages, cosmids are the main cloning vectors used in the process of recombinant technology.

The procedure for selecting cloning vectors are as follows:

  1. The vectors should have the ability to replicate autonomously within the host cell.
  2. The vectors should be easily introduced into the host cell and should be isolated again.
  3. The vectors should contain specific restriction sites, which can be broken easily by the restriction endonuclease enzyme. The foreign DNA can be inserted easily at the restriction site.
  4. The vector should have a marker site that allows easy detection of transformed cells.
  5. The transformation should be easy and perfect.
  6. For the expression of desired foreign DNA, the vector should have some regulatory elements like a promoter, operator, etc.

Q.2. Comment on PBR 322 plasmid.

Sol: PBR 322 plasmid is the most commonly used plasmid vector. In this plasmid the two marker sites – TetR (Tetracycline resistant) and AmpR (Ampicillin resistant) are found. It contains the recognition sites for 12 different restriction enzymes. The desired DNA is inserted in between the TetR and AmpR gene with the help of the restriction enzymes.

The below diagram explains the structure of PBR 322 plasmid.

PBR 322 plasmid

 

Q.3. Write a brief account of various cloning vectors used in the process of recombinant rDNA technology.

Sol: The different cloning vectors used in the process of recombinant rDNA technology are:

Plasmids

  • These are extrachromosomal components in the bacterial cell.
  • The DNA is a circular and double-stranded molecule.
  • They contain an origin of the replication site and can replicate independently of a bacterial chromosome.
  • They have specific restriction sites where the desired gene can be incorporated.
  • They have a marker site.
  • The plasmid may contain three to one thousands of genes in it.

Bacteriophage

  • The viruses which infect bacteria and cause lysis of bacterial cells are called bacteriophage.
  • Example: ((ƛ) ) Lambda phage and M13 phage.
  • A bacteriophage is a better vector as compared to plasmids.
  • Large DNA segments (24 Kbp) can be cloned in the bacteriophage.
  • Each bacteriophage produces a plaque in the culture. Hence, their identification is easy.

Cosmids.

  • This is a hybrid of plasmid and ((ƛ) ) Lambda phage.
  • These cosmids can replicate within the host cells just like a plasmid.
  • Due to the presence of Cos site, these cosmids are packed like phage particles.
  • Cosmids can be used to clone the DNA segments of up to 45kbp.

Q.4. Write short notes on Southern blotting technique and DNA fingerprinting.

Sol:

Southern blotting technique

This technique is used for the analysis of the DNA segments. This was developed by E.M.Southern in 1975. Hence named as southern blotting. In this technique, the DNA segments are transferred on a nitrocellulose filter. These are then identified by the hybridization with the DNA probes.

DNA fingerprinting.

DNA fingerprinting is a technique that shows the genetic makeup of living things. It is a method of finding the difference between the satellite DNA regions in the genome. This technique was discovered by Alec Jeffreys and co-workers during the 1980s. In this method, the DNA of a specific person is cut into smaller segments and is separated in the form of bands by the process of electrophoresis. The identity of a person can be established by a specific sequence found in the DNA of the person. This technique is used in resolving disputed paternity of any child and in detecting genetic disease prior to the birth of a child. It is also used in the identification of criminals.

Q.5. Write short notes on Polymerase Chain Reaction and Restriction enzyme

Sol:

Polymerase Chain Reaction

PCR or Polymerase Chain Reaction is a technique used in molecular biology to create several copies of a certain DNA segment. It analyzes short sequences of DNA or RNA even in samples containing minute quantities of DNA or RNA. This technique was developed in 1983 by Kary Mullis, an American biochemist. PCR has made it possible to generate millions of copies of a small segment of DNA. This tool is commonly used in the molecular biology and biotechnology labs.

Restriction enzyme

The restriction enzyme is a protein produced by bacteria that cleaves the DNA at specific sites. This site is known as the restriction site. These enzymes protect the live bacteria from bacteriophages. They recognize and cleave at the restriction sites of the bacteriophage and destroy its DNA. Restriction enzymes are important tools for genetic engineering. They can be isolated from the bacteria and used in the laboratories.

Q.6. What is Recombinant DNA Technology? Brief out the process of Recombinant DNA Technology.

Sol: The technology used for producing artificial DNA through the combination of different genetic materials (DNA) from different sources is referred to as Recombinant DNA Technology. Recombinant DNA technology is popularly known as genetic engineering.

The recombinant DNA technology emerged with the discovery of restriction enzymes in the year 1968 by Swiss microbiologist Werner Arber,

Inserting the desired gene into the genome of the host is not as easy as it sounds. It involves the selection of the desired gene for administration into the host followed by a selection of the perfect vector with which the gene has to be integrated and recombinant DNA formed.

Thus, the recombinant DNA has to be introduced into the host. And at last, it has to be maintained in the host and carried forward to the offspring.

Process of Recombinant DNA Technology

The complete process of recombinant DNA technology includes multiple steps, maintained in a specific sequence to generate the desired product.

Step-1. Isolation of Genetic Material.

The first and the initial step in Recombinant DNA technology is to isolate the desired DNA in its pure form i.e. free from other macromolecules.

Step-2.Cutting the gene at the recognition sites.

The restriction enzymes play a major role in determining the location at which the desired gene is inserted into the vector genome. These reactions are called restriction enzyme digestions.

Step-3. Amplifying the gene copies through Polymerase chain reaction (PCR).

It is a process to amplify a single copy of DNA into thousands to millions of copies once the proper gene of interest has been cut using the restriction enzymes.

Step-4. Ligation of DNA Molecules.

In this step of Ligation, joining of the two pieces – a cut fragment of DNA and the vector together with the help of the enzyme DNA ligase.

Step-5. Insertion of Recombinant DNA Into Host.

In this step, the recombinant DNA is introduced into a recipient host cell. This process is termed as Transformation. Once after the insertion of the recombinant DNA into the host cell, it gets multiplied and is expressed in the form of the manufactured protein under optimal conditions

Q.7. What is the importance of genetic engineering?

Sol: Scientists working in the field of biotechnology have succeeded in achieving results which have proved advantageous in the field of medical science, agriculture and industries. By using these techniques it has become possible to improve the variety of agricultural crops and domestic animals and also the quality of other industrial products. Some important achievements of genetic engineering are as follows:

  • Cloning of Nitrogen fixation(Nif) gene in cereal crops.
  • Cloning of the Haemophilic gene.
  • Cloning of Hepatitis B virus gene.
  • Cloning of Human growth hormone and insulin gene.
  • Cloning of penicillin G acylase gene for the production of penicillin

Q.8.What are the molecular probes? List out the importance of molecular probes.

Sol: The segment of DNA or RNA with the help of which C-DNA or RNA segments of some organisms can be identified are called molecular probes.

The molecular probes are of the following types. DNA probes and RNA probes.

Importance of molecular probes.

  1. The probes are used to identify the specific DNA segments used in the research of genetic engineering.
  2. Pollutants in food can be detected with the help of molecular probes.
  3. The molecular probes are used in the field of forensic science, in resolving disputed paternity issues and establishing family relationships.
  4. These molecular probes can also be used to identify the improved variety of crops and hybridized seed of crops.

Q.9. What are the different enzymes used in the process of genetic engineering?

Sol: The different enzymes used in the process of genetic engineering are

RNA dependent DNA polymerase.

These enzymes function by polymerising the nucleotides of DNA strands on the RNA template.

DNA dependent DNA polymerase.

This enzyme functions by polymerising the nucleotides of complementary DNA strands on the template of the DNA.

Ligases – This enzyme functions by attaching the ends of the DNA fragment on the template.

Lysozymes – This enzyme functions by dissolving the cell wall of bacteria so that the DNA of bacteria can be isolated.

Alkaline phosphates – This enzyme functions by cutting the phosphate at 5′ or 5 prime ends of the circular DNA and helps in keeping the DNA linear, so that the foreign DNA can be inserted on it. This enzyme also prevents the circular nature of DNA from forming again.

Q.10. What is PCR – Polymerase Chain Reaction? List out the applications of PCR.

Sol: Sol: Polymerase Chain Reaction (PCR) is a technique used for creating several copies of a certain DNA segment. This technique was developed in 1983 by Kary Mullis, an American biochemist. PCR has made it possible to generate millions of copies of a small segment of DNA. This tool is commonly used in the molecular biology and biotechnology labs.

The following are the applications of PCR :

In Medicine

  • Testing of genetic disease mutations.
  • Monitoring the gene in gene therapy.
  • Detecting disease-causing genes in the parents.

In Forensic Science

  • Paternity tests.
  • Used as a tool in genetic fingerprinting.
  • Identifying the criminal from millions of people.

In Research and Genetics

  • Gene Mapping.
  • Analysis of gene expression.
  • Compare the genome of two organisms in genomic studies.
  • In the phylogenetic analysis of DNA from any source such as fossils.

Q.11. Explain the process of nomenclature of restriction enzymes.

Sol: Restriction enzymes are like molecular scissors which function by cutting the DNA molecules at a specific site. These enzymes are naturally found in E.Coli, Bacillus, Streptococcus, etc.

The nomenclature of restriction enzymes are as follows:

  • The first letter of an enzyme represents the genus from which it has been isolated. This is written in capital letters.
  • The two letters after this represent the species of the genus. These are written in a small letter. These three letters are written in italics.

For example- Eco – E, Coli – from Escherichia coli

  • The fourth letter represents the strain of a genus and is written from which it has been isolated.

For example- Eco R – from R strain of E.coli

  • If more than one restriction enzymes are obtained from one organism, these are represented by a roman number.

For example- Eco-R I Eco-RII, etc.

Q.12.Explain in detail about the plasmid as a cloning vector.

Sol: Plasmids are a small, circular piece of DNA that is not the same as chromosomal DNA. Its ability to replicate is independent of chromosomal DNA. They are usually found in bacteria, but they are also present in multicellular organisms. The word Plasmid was first coined by Joshua Lederberg in 195.

Functions of Plasmids.

Plasmids have various functions, as they:

  • Facilitate the process of replication.
  • Increase the survival of the organism.
  • Carry the helpful genes to their host organisms.
  • Plasmids are frequently used as a cloning vector in the DNA recombinant technology.

Features of Plasmids.

Following are the important features of Plasmids

  • These plasmids have extrachromosomal components.
  • They have marker genes or marker sites within the plasmids.
  • The plasmid may contain three to one thousands of genes in it.
  • These plasmids are not necessary for the growth and survival of bacteria.
  • They contain specific restriction sites where the desired gene can be inserted.
  • These plasmids are circular in shape and consist of double-stranded DNA molecules.
  • They contain an origin of replication. Therefore, it is able to replicate independently within the cell.

Q.13. Do All Bacteria Have Plasmids? Draw the structure of Plasmids in bacterial cells.

Sol: Yes, Plasmids naturally exist in all bacterial cells. It functions by:

  1. Helps in their survival by producing toxins,
  2. Facilitate the process of replication in bacteria.
  3. Few plasmids contain genes that help in food digestion.
  4. The R plasmids help a bacterial cell by defending against environmental factors such as antibiotics, poison, etc.

The structure of Plasmids in bacterial cells.

 Plasmids in bacterial cells

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