RBSE Solutions Class 12 Biology Chapter 15 Genetic Engineering

RBSE Class 12 Biology Chapter 15 Multiple Choice Questions

 

Question 1. Which of the following enzyme cut DNA at a specific site?
(a) Ligase
(b) Polymerase
(c) Restriction Endonuclease
(d) All of the options
Answer: (c) Restriction Endonuclease
In simple words: Restriction endonucleases are special enzymes that can cut DNA at specific points. They act like molecular scissors in genetic engineering.

🎯 Exam Tip: Remember that restriction endonucleases are crucial for cutting DNA precisely, allowing new DNA segments to be inserted.

 

Question 2. Restriction endonuclease enzyme is found naturally in?
(a) Bacteria
Answer: (a) Bacteria
In simple words: These enzymes are naturally present in bacteria, where they help protect the bacteria from foreign DNA, like viruses, by cutting it up.

🎯 Exam Tip: Know that bacteria use restriction enzymes as a defense mechanism against viruses, which is why they are found there naturally.

 

Question 3. DNA Vector is?
(a) Plasmid
(b) cDNA
(c) Synthesized DNA
(d) All of the options
Answer: (a) Plasmid
In simple words: A DNA vector is like a carrier that helps move desired DNA into a host cell. Plasmids are commonly used as such carriers.

🎯 Exam Tip: When asked about DNA vectors, remember that plasmids are the most frequently cited example due to their ability to carry and replicate foreign DNA.

 

Question 4. M13 is an example of?
(a) Plasmid
(b) Bacteriophage
(c) Cosmid
(d) All of the options
Answer: (b) Bacteriophage
In simple words: M13 is a type of virus that infects bacteria. These viruses, called bacteriophages, are often used as vectors in genetic engineering.

🎯 Exam Tip: For examples of vectors, distinguish between plasmids and bacteriophages. M13 is a classic example of a bacteriophage used as a cloning vector.

 

Question 5. Which of the Blotting technique is used in the identification of DNA segments?
(a) Genomic DNA
(b) Western
(c) Southern
(d) Northern
Answer: (c) Southern
In simple words: Southern blotting is a specific lab method used to find and identify particular DNA segments. It helps scientists see specific DNA patterns.

🎯 Exam Tip: Clearly differentiate between blotting techniques: Southern for DNA, Northern for RNA, and Western for proteins. Matching the right technique to the molecule is key.

 

Question 6. Which enzyme joins free DNA ends?
(a) Restriction endonuclease
(b) Ligases
Answer: (b) Ligases
In simple words: Ligases are like molecular glue; they connect broken or free ends of DNA pieces, making a continuous DNA strand.

🎯 Exam Tip: Understand the opposing functions of restriction enzymes (cut DNA) and ligases (join DNA). Both are essential in genetic engineering.

 

Question 7. Jumping genes are called?
(a) Phasmid
(b) Plasmid
(c) Cosmid
(d) Transposons
Answer: (d) Transposons
In simple words: Jumping genes are DNA segments that can move from one place to another within a cell's genome. They are scientifically known as transposons.

🎯 Exam Tip: Remember the term "transposons" as the scientific name for "jumping genes." This movement can cause changes in gene expression.

 

Question 8. Mullis discovered in 1989?
(a) Plasmid
(b) Polymerase chain reaction
(c) Southern Blotting technique
(d) Western Blotting technique
Answer: (b) Polymerase chain reaction
In simple words: Kary Mullis developed the Polymerase Chain Reaction (PCR) in 1989. This method is used to make many copies of a specific DNA segment.

🎯 Exam Tip: Link Mullis's name directly to the invention of PCR, a groundbreaking technique for DNA amplification.

 

Question 9. C-DNA is used in the formation of?
(a) tRNA
(b) mRNA
(c) rRNA
(d) DNA
Answer: (b) mRNA
In simple words: C-DNA stands for complementary DNA. It is made from messenger RNA (mRNA) using a special enzyme called reverse transcriptase.

🎯 Exam Tip: Know that cDNA is synthesized from mRNA and lacks introns, making it useful for expressing genes in prokaryotes.

 

Question 10. Which of the following is a source of EcoRI?
(a) Bacteria
Answer: (a) Bacteria
In simple words: EcoRI is a type of restriction enzyme, and like all restriction enzymes, it comes from bacteria. Bacteria use these enzymes to cut foreign DNA.

🎯 Exam Tip: Recognize EcoRI as a common restriction enzyme and remember its origin is always bacterial.

RBSE Class 12 Biology Chapter 15 Very Short Answer

 

Question 1. Who is credited for developing recombinant DNA Technique (RDT)?
Answer: Stanley Cohen and Herbert Boyer, along with others, are credited with developing the recombinant DNA technique in 1973. This was a big step in genetics.
In simple words: Stanley Cohen and Herbert Boyer are known for creating recombinant DNA technology in 1973.

🎯 Exam Tip: When answering "who discovered," always include the names of the main scientists and the year if known, as it shows complete knowledge.

 

Question 2. Define recombinant DNA technology?
Answer: Recombinant DNA technology involves various methods used to change the genetic makeup (DNA) of an organism by adding new genetic material. This process is used to create organisms with desired traits.
In simple words: Recombinant DNA technology means changing an organism's DNA by adding new DNA parts to it.

🎯 Exam Tip: A good definition includes both the "what" (modifying DNA) and the "how" (incorporating changes) aspects of the technology.

 

Question 3. What are cloning vectors?
Answer: In recombinant DNA technology, cloning vectors are carriers. They are DNA molecules that can carry a desired gene into a host cell, like a plant or animal cell, and then replicate their own DNA inside that cell. Plasmids, bacteriophages, and cosmids are common types of cloning vectors.
In simple words: Cloning vectors are DNA carriers that take a desired gene into a cell and help it make copies. Plasmids and bacteriophages are examples.

🎯 Exam Tip: Remember to name the key examples of cloning vectors (plasmids, bacteriophages, cosmids) in your answer to show a comprehensive understanding.

 

Question 4. What is meant by molecular probes?
Answer: Molecular probes are small pieces of DNA or RNA that are used to find and identify specific DNA or RNA segments from an organism. They work by binding to their complementary sequences. The molecular probes are of the following types:

• DNA probes
• RNA probes

In simple words: Molecular probes are short DNA or RNA pieces used to find specific matching DNA or RNA parts in a sample.

🎯 Exam Tip: Explain that molecular probes are labeled (often radioactively or fluorescently) to make them detectable after they bind to their target.

The type of gene used in genetic engineering creates special features in the modified cells. This specific gene, which is put into the vector DNA, is called a marker gene. For example, a Kanamycin resistant gene helps in selecting cells that have taken up the new DNA.

🎯 Exam Tip: Understand that marker genes are crucial for identifying which cells have successfully received the recombinant DNA from the vector.

 

Question 6. What are reporter genes? Give examples.
Answer: Reporter genes are special genes that, besides marker genes, cause a visible or measurable change in the host cell. These changes make the cells containing these genes look or behave differently from other cells, helping scientists to easily identify them. For example, the LUC gene, found in fireflies (Jugnoo), produces bioluminescence, making the cells glow.
In simple words: Reporter genes create a visible effect in cells, helping scientists to easily see which cells have received the new gene. An example is the firefly LUC gene that makes cells glow.

🎯 Exam Tip: Clearly distinguish reporter genes (cause observable effects) from marker genes (used for selection, often antibiotic resistance). Give a concrete example for better marks.

 

Question 7. What is the genomic library?
Answer: A genomic library is a complete collection of all the cloned DNA segments that represent the entire genome of an organism. It is made by taking out all the DNA from a single haploid set of chromosomes of an organism and cloning it.
In simple words: A genomic library is a full collection of all the cloned DNA pieces from an organism's entire genetic material.

🎯 Exam Tip: Emphasize that a genomic library contains the *entire* genome, including both coding and non-coding regions.

 

Question 8. What are Cosmids?
Answer: Cosmids are a type of hybrid vector, combining features of both plasmids and lambda (λ) phages. They are essentially plasmids that have the 'Cos' site DNA sequence from a lambda phage inserted into them. This allows them to carry large DNA fragments.
In simple words: Cosmids are special DNA carriers made by mixing parts of plasmids and lambda phages, used to carry big DNA pieces.

🎯 Exam Tip: Highlight that Cosmids are hybrid vectors and their key feature is the ability to clone larger DNA segments compared to standard plasmids.

 

Question 9. Define the restriction endonuclease enzyme.
Answer: A restriction endonuclease enzyme is an enzyme that cuts DNA molecules at very specific recognition sites. These enzymes are often called "molecular scissors" because they can precisely cut DNA into smaller segments at particular sequences.
In simple words: Restriction endonuclease enzymes cut DNA at exact spots, acting like tiny scissors for genes.

🎯 Exam Tip: When defining, always include the phrase "specific sites" or "recognition sequences" to show precise cutting, not random cutting.

 

Polyacrylamide gel.

🎯 Exam Tip: While 'Polyacrylamide gel' can be a medium for separating molecules, ensure you understand its specific use in various techniques like gel electrophoresis for proteins or DNA.

 

Question 11. Write a full form of RFLP.
Answer: RFLP stands for Restriction Fragment Length Polymorphism. It is a technique used in genetics.
In simple words: RFLP means Restriction Fragment Length Polymorphism, a method for checking differences in DNA segments.

🎯 Exam Tip: For full forms, spell out each word clearly and correctly. Briefly mention its application if space permits, as it enhances your answer.

RBSE Class 12 Biology Chapter 15 Short Answer Questions

 

Question 1. What are cloning vectors? Write a brief account of various cloning vectors used in recombinant rDNA technology?
Answer: After a desired gene or genes are isolated, a vector is needed to carry this gene into a host cell, where it can replicate its DNA. These carriers are called cloning vectors and are essential in recombinant DNA technology. Plasmid, Bacteriophages, and Cosmids are the main types of cloning vectors used.
Plasmids:

• These are small, circular, extrachromosomal DNA molecules found in bacteria.
• They are double-stranded and can replicate on their own.
• Plasmids have a specific site where replication starts and can replicate independently.
• They also have specific sites where the desired gene can be inserted.
• Plasmids possess marker sites, which help in identifying cells that have taken up the plasmid.
• A plasmid can carry between 3 and 1000 genes.

Bacteriophage:

• These are viruses that infect bacteria and cause the bacterial cell to break open (lysis).
• Examples include lambda (λ) phage and M13 phage.
• Bacteriophages are often better vectors than plasmids because they can carry larger DNA segments.
• Large DNA segments (up to 24 Kbp) can be cloned using bacteriophages.
• Each bacteriophage forms a clear area called a plaque in a bacterial culture, which makes them easy to identify.

Cosmid:
In simple words: Cloning vectors are DNA molecules that carry new genes into host cells and help them multiply. Plasmids are circular DNA in bacteria, bacteriophages are viruses that infect bacteria, and cosmids are a mix of both. Each has specific features making them useful for carrying different sizes of genes.

🎯 Exam Tip: When discussing different types of vectors, clearly list their key characteristics, especially their capacity for DNA insertion and ease of identification.

 

Question 2. Comment on PBR 322 plasmid.
Answer: The pBR322 plasmid is a widely used and important plasmid vector in genetic engineering. It contains two marker genes: TetR, which provides resistance to Tetracycline, and AmpR, which provides resistance to Ampicillin. This plasmid also has specific recognition sites for 12 different restriction enzymes. Scientists insert the desired foreign DNA into the pBR322 plasmid between the TetR and AmpR genes using a restriction enzyme. This strategy helps in selecting recombinant cells.

Structure of pBR 322 plasmid

In simple words: pBR322 is a common plasmid used as a carrier in genetic engineering. It has genes for resistance to Tetracycline and Ampicillin, and specific spots where new DNA can be added by special enzymes.

🎯 Exam Tip: When describing pBR322, mention its two antibiotic resistance genes (TetR and AmpR) and the presence of multiple restriction sites, as these are its defining features for cloning.

 

Question 3. Write a short note on:
1. Southern Blotting technique.
2. DNA Fingerprinting.
3. Polymerase Chain Reaction.
4. Nomenclature of Restriction Enzymes.
5. Features of Vectors.
Answer:
2. DNA Fingerprinting: This technique was developed by Alec Jeffreys and his team in 1985. It involves cutting a person's DNA into small pieces and then separating these pieces into bands using a method called electrophoresis. A person's unique identity can be confirmed by looking at the specific pattern of these DNA segments. This method is used to solve family disputes (like paternity cases) and to detect genetic diseases before a baby is born. It is also very helpful in identifying criminals in crime investigations.
3. Polymerase Chain Reaction (PCR): Kary Mullis discovered PCR in 1989. It is a powerful lab method that can quickly make millions of copies of a single DNA molecule without needing vectors (carriers). This process is carried out in a DNA thermal cycler. By repeating the cycle 20-30 times, many copies of DNA are produced.
4. Nomenclature of Restriction Enzymes: The naming system for restriction enzymes follows specific rules:

• The first letter of the enzyme's name comes from the genus (group) of the organism it was isolated from and is always a capital letter.
• The next two letters represent the species of that genus and are written in small, italicized letters. For example, 'E co' comes from *Escherichia coli*.
• The fourth letter (or word) shows the specific strain of the species from which the enzyme was isolated. For instance, 'Eco R' means it's from the R strain of *E.coli*.
• If more than one restriction enzyme is found in the same organism (or strain), they are numbered using Roman numerals (e.g., Eco RI for the first, Eco RII for the second).

5. Features of Vectors: For a DNA molecule to be a good vector, it needs certain features:

• It must be easy to put into a host cell and also easy to get out of it.
• It should be able to make copies of itself freely inside the host cell.

In simple words: DNA fingerprinting identifies people using their unique DNA patterns. PCR makes many DNA copies fast without needing carriers. Restriction enzymes are named based on the bacteria they come from. Good vectors must be easy to insert, extract, and replicate within a host cell.

🎯 Exam Tip: For a multi-part question, address each point separately. Provide key details like discoverers and years where appropriate, and use bullet points for clarity in lists.

 

Question 4. Explain the process of forming the Genomic Library.
Answer: A genomic library is a collection of all the complete DNA content from a haploid set of chromosomes (the entire genome) of an organism. It is created by first isolating all the DNA from a cell. The process to form a genomic library is as follows:
Complete genome of Donor Cell
\( \downarrow \)
Restriction endonuclease enzyme
\( \downarrow \)
DNA fragment
\( \downarrow \)
Vector DNA \( + \) DNA ligase
\( \downarrow \)
Circular Recombinant DNA
\( \downarrow \)
Insertion into Bacterial cell (host cell)
\( \downarrow \)
Polymerization
\( \downarrow \)
Identification through DNA Probe
\( \downarrow \)
Genomic Library / DNA Library
In simple words: To make a genomic library, all the DNA from an organism is first cut into pieces. These pieces are then put into vectors and inserted into bacteria. The bacteria copy the DNA, creating a collection of all the organism's genes.

🎯 Exam Tip: When explaining a process, use a flowchart-like structure or clear sequential steps. Start with DNA isolation and end with the final library, including key enzymes like restriction endonuclease and ligase.

 

Question 5. Write a short note on the importance of Bacteriophage as a clonal vector.
Answer: Bacteriophages are better vectors than plasmids for several reasons. They are viruses that infect bacteria. When they are used, large fragments of DNA, specifically up to 24 Kb, can be cloned. Also, each bacteriophage produces a clear spot (plaque) in a bacterial culture, which makes testing and identification very easy.
Lambda (λ) phage is commonly used as a vector over M13 phage due to the following reasons:

• They are bacteriophages that specifically infect *E.coli*.
• Their DNA is linear and double-stranded.
• Non-essential parts of their DNA can be removed, which reduces the vector's size. This allows larger foreign DNA segments to be easily inserted.

In simple words: Bacteriophages are good gene carriers because they can hold larger DNA pieces and are easy to find after cloning. Lambda phage is better than M13 because it's linear and parts can be removed to make space for more DNA.

🎯 Exam Tip: Focus on the advantages of bacteriophages (larger insert size, easy detection) when comparing them to other vectors like plasmids.

RBSE Class 12 Biology Chapter 15 Essay Type Questions

 

Question 1. Write about different stages of techniques of recombinant DNA technology.
Answer: Recombinant DNA technology involves several key stages to manipulate genetic material effectively:
1. Identification and Isolation of Desired Gene: The first step is to find and separate the specific gene or DNA segment that is needed. This isolation process is done using restriction endonuclease enzymes. Werner Arber and Hamilton O. Smith discovered restriction endonuclease enzymes in 1970.
Restriction Endonuclease:

• These enzymes act like molecular scissors, cutting DNA at specific sites.
• They are naturally found in bacteria such as *E.coli*, *Bacillus*, *Streptococcus*, and *Thermus aquaticus*.
• There are three main types of restriction endonuclease enzymes: Type I, Type II, and Type III.

Nomenclature of Restriction Endonuclease: The naming convention for these enzymes is:

• The first letter of the enzyme's name comes from the genus of the organism it was isolated from, always written in a capital letter.
• The next two letters represent the species of that genus, written in small, italicized letters (e.g., Eco from *Escherichia coli*, Hin from *Haemophilus influenza*).
• The fourth letter or word indicates the strain of the genus from which the enzyme was isolated (e.g., Eco R from R strain of *E.coli*).
• If multiple restriction enzymes are obtained from the same organism, they are numbered with Roman numerals.

When DNA segments from two different sources are mixed with DNA ligase enzyme, they join together by phospho-di-ester bonds to form a double-stranded structure.
Other Enzymes used in Genetic Engineering:

• RNA dependent DNA Polymerase: This enzyme helps in making a DNA strand from an RNA template.
• DNA dependent DNA Polymerase: This enzyme helps in making a complementary DNA strand from a DNA template.
• Ligase: This enzyme joins the ends of DNA segments together on the template.
• Lysozymes: These enzymes dissolve the cell wall of bacteria, making it easier to isolate bacterial DNA.
• Alkaline Phosphatases: This enzyme cuts the phosphate at the 5' end of circular DNA and helps keep it in a linear form. This prevents the DNA from becoming circular again, allowing foreign DNA to be inserted.

2. Selection of Cloning Vectors: After isolating the desired gene with a restriction endonuclease, this gene-containing DNA segment is placed into a suitable vector. This vector must be able to enter the target host or receptor cell and replicate its DNA inside that host cell.
Essential features of Vector:

• It should be easy to insert into the host cell and also easy to isolate.
• It should be able to replicate freely within the host cell.

In simple words: Recombinant DNA technology starts by finding and cutting a specific gene using special enzymes called restriction endonucleases. These enzymes are named based on where they come from. Other enzymes like ligase (to join DNA) and polymerases (to make DNA copies) are also used. Then, this gene is put into a vector, which is a carrier that takes the gene into a host cell. A good vector needs to be easy to use and able to make many copies of the gene inside the host.

🎯 Exam Tip: For essay questions, break down the answer into clear stages with sub-headings. Define key terms and provide examples of enzymes and their functions to demonstrate in-depth knowledge.

Note: In *E.coli*, both natural and man-made vectors can be used.

🎯 Exam Tip: Remember that *E.coli* is a popular model organism in genetic engineering due to its well-understood genetics and ease of manipulation with various vectors.

Some important vectors used in *E.coli* are:
1. Plasmid
2. Bacteriophage
3. Cosmid

🎯 Exam Tip: Listing common examples of vectors for *E.coli* (Plasmid, Bacteriophage, Cosmid) is helpful when discussing vector selection.

1. Plasmid: Lederber first observed plasmids as extrachromosomal material in bacterial cells in 1952. They have the following important features:

• Plasmids are extrachromosomal components, meaning they are separate from the main bacterial chromosome.
• They are circular, double-stranded DNA molecules.
• They contain an origin of replication (ori), which allows them to replicate independently within the cell.

In simple words: Plasmids are small, circular DNA pieces found in bacteria that exist separately from the main chromosome. They can make copies of themselves on their own.

🎯 Exam Tip: When describing plasmids, always mention their circular nature, independent replication, and extrachromosomal location.

1. These contain specific restriction sites where the desired gene can be inserted.
2. Marker genes or marker sites are also found.
3. The plasmid may contain three to one thousand genes.
Note: The most commonly used plasmid vector is pBR322. In this plasmid, two marker sites, TetR (Tetracycline resistant) and AmpR (Ampicillin resistant), are found. It also contains recognition sites for 12 different restriction enzymes. The desired DNA (foreign DNA) is inserted between the TetR and AmpR genes with the help of a restriction enzyme.
In simple words: Plasmids have special spots for adding new genes, and they also have markers to show if the gene was successfully added. pBR322 is a common plasmid with two resistance genes and many cut sites for inserting foreign DNA.

🎯 Exam Tip: Understand that restriction sites allow precise gene insertion, and marker genes are essential for identifying successful gene transfer in cloning experiments.

 

Question 1. What are cloning vectors? Write a brief account of various cloning vectors used in recombinant rDNA technology?
Answer: After isolating the desired gene, a vector is needed. This vector helps to insert the gene into a host cell, where it can then multiply its DNA. This type of carrier is called a cloning vector. Plasmids, bacteriophages, and cosmids are the main types of cloning vectors used in recombinant DNA technology.

Here are some important vectors:

Plasmids:
• These are extra pieces of DNA found in bacterial cells, separate from the main chromosome.
• The DNA is a circular and double-stranded molecule.
• They have a special spot called the 'origin of replication' and can make copies of themselves without the main bacterial chromosome.
• They have specific cutting points (restriction sites) where the desired gene can be added.
• They also have marker sites to help identify them.
• A plasmid can hold anywhere from 3 to 1000 genes.

Note on Plasmids/Episomes: Depending on how they copy, extra chromosomal material in bacteria is called a plasmid or episome. A plasmid can replicate on its own, but an episome only replicates when attached to the bacterial chromosome.

Bacteriophages:
• These are viruses that infect bacteria. They cause the bacterial cell to break open.
• Examples include Lambda (λ) phage and M13 phage.
• Bacteriophages are considered better vectors than plasmids.
• They can carry large DNA segments, up to 24 Kbp (kilobase pairs).
• Each bacteriophage creates a clear spot (plaque) in the culture, making them easy to identify.

A Lambda (λ) phage is more widely used as a vector than M13 because of the following reasons:
• They are bacteriophages of E.coli.
• Their DNA is linear and double-stranded.
• Non-essential parts of a phage DNA can be removed, which reduces the vector's size. This allows larger foreign DNA segments to be inserted easily. Foreign DNA of 5-10 Kb can be inserted or incorporated.

Cosmids:
• A cosmid is a hybrid of a plasmid and a Lambda (λ) phage.
• They contain 'Cos' sites from the Lambda phage. These sites allow them to be packaged like lambda phage particles.
• Cosmids can be used to clone DNA segments up to 45 Kbp in size.
• An example is CosmidPLFR-5.
• Cosmids have two Cos sites, 6 restriction endonuclease sites, an origin of replication site, and genes for tetracycline antibiotic resistance.

Additional Vectors: Besides plasmids, bacteriophages, and cosmids, other vectors are also used in genetic engineering. These include:
• Phagemids
• Shuttle vectors
• Transposons

Transposons are also known as Jumping genes.
In simple words: Cloning vectors are tools that carry new genes into cells and help them multiply. Plasmids, bacteriophages, and cosmids are the main types, each with unique features like circular DNA or the ability to carry large genes, making them useful for different tasks in genetic engineering. Other vectors like phagemids and transposons are also used.

🎯 Exam Tip: Remember the key characteristics of each type of cloning vector, especially their DNA structure, replication ability, and the size of DNA fragments they can carry, as these are crucial for selection in genetic engineering.

 

Question 1. Write about different stages of techniques of recombinant DNA technology.
Answer:
(Continued from previous sections. The first two stages, 'Identification and Isolation of Desired Gene' and 'Selection of Cloning Vectors', have been detailed.)

3. Insertion of the desired gene in the cloning vector:
To insert the desired gene into a cloning vector, similar restriction sites are first created in both the gene and the vector. After this, both are joined together because they share the same restriction sites. This process is called Ligation.
The following enzymes are required for this process:
1. Restriction endonucleases

4. Multiplication of recombinant DNA in host cell:
Recombinant DNA can be inserted into the host cell using two main methods:
1. Transformation
2. Transduction
In this process, E.coli bacteria are mainly used as the host cells. The recombinant DNA multiplies inside the E.coli cells through these processes (Transformation and Transduction), which involve taking up foreign DNA and integrating it.

5. Identification of the cloned gene and its transfer in other organisms:
• We use certain genes, like antibiotic-resistant genes or the LacZ gene (which makes β-galactosidase), as marker genes. If DNA is inserted into these marker genes at cloning sites, the genes become non-functional. This is called insertional inactivation.
• We can identify recombinants from non-recombinants based on whether the marker gene expresses or not.
• Besides marker genes, some other genes, called reporter genes, produce specific features. These cause the cells containing them to look different from other cells.
• For example, the LUC (Luciferase) gene found in fireflies ("Jugnoo") produces bioluminescence, making cells glow.
In simple words: To make recombinant DNA, the desired gene is first cut and put into a vector. Then, this new DNA is multiplied in host cells like E.coli. Finally, special marker genes help scientists find and identify the cells that successfully took up the new DNA.

🎯 Exam Tip: When describing the stages, clearly differentiate between transformation (direct DNA uptake) and transduction (DNA transfer via virus) for multiplication, and explain the role of marker/reporter genes in identification.

 

Question 2. Describe different blotting techniques in details.
Answer:
Blotting Technique:
In this method, DNA segments are first separated on an agarose gel using electrophoresis. These separated segments are then transferred and fixed onto a nitrocellulose filter. They are then identified by hybridization with DNA probes. This entire procedure is known as the blotting technique.

1. Southern Blotting Technique:
E.M. Southern first developed this method in 1975. He transferred DNA segments onto a nitrocellulose filter. This technique was named Southern blotting. It is used to analyze DNA segments.

2. Northern Blotting Technique:
Alwin et al. (1979) transferred RNA segments after electrophoresis onto an amino benzyl oximetry (OBM) membrane, instead of a nitrocellulose filter. This technique was named Northern blotting. It is used to analyze RNA segments.

3. Western Blotting Technique:
Tobin et al. (1979) first broke down proteins into smaller polypeptide chains using sodium-dodecyl sulphate (SDS). After separating these polypeptides by electrophoresis, they were transferred onto a nitrocellulose filter or nylon membrane. These were then detected on an X-ray plate, and the proteins were identified. This technical analysis of proteins is called Western blotting technique.
In simple words: Blotting techniques are lab methods to find specific molecules. Southern blotting finds DNA, Northern blotting finds RNA, and Western blotting finds proteins. They all involve separating molecules, transferring them to a filter, and then using probes or antibodies to identify the target molecule.

🎯 Exam Tip: Distinguish between Southern, Northern, and Western blotting based on the biomolecule they detect (DNA, RNA, and protein, respectively). Be sure to mention the transfer medium used for each technique.

 

Question 3. Write a detailed account on plasmid as a cloning vector.
Answer:
Plasmid:
Lederber (1952) first observed plasmids as extra pieces of DNA in bacterial cells, separate from the main chromosome. Plasmids have the following important features:
• These are extra pieces of DNA (other than the main chromosomal DNA).
• These are circular, double-stranded DNA molecules.
• They contain an origin of replication (ori), which allows them to replicate independently within the cell.
• They contain specific restriction sites where the desired gene can be inserted.
• Marker genes or marker sites are also found on them.
• A plasmid may contain three to one thousand genes.

The most commonly used plasmid vector is pBR322. This plasmid has two marker sites: TetR (Tetracycline resistant) and AmpR (Ampicillin resistant). It also contains recognition sites for 12 different restriction enzymes. The desired DNA (foreign DNA) is inserted between the TetR and AmpR genes with the help of a restriction enzyme.
In simple words: Plasmids are small, circular DNA found in bacteria that can copy themselves. They have special places to insert new genes and markers to help scientists find them, making them very useful for carrying and multiplying foreign DNA in experiments.

🎯 Exam Tip: When describing plasmids as cloning vectors, highlight their key features such as circular DNA, independent replication, and the presence of marker genes and restriction sites, as these make them ideal for gene transfer. Mentioning pBR322 as a common example helps demonstrate specific knowledge.

 

Question 4. What do you understand by molecular probes? Explain its utility.
Answer:
Molecular Probes:
Molecular probes are segments of DNA or RNA that help identify specific C-DNA or RNA segments of an organism. They act like 'tags' that stick to the matching genetic material.

Molecular probes can be of the following types:
• DNA probes
• RNA probes

Importance of Probes:
• They are used in genetic engineering research to identify specific DNA segments.
• They can detect pollutants in food.
• In forensic science, they are used to solve paternity disputes and establish family relationships.
• They can also identify improved varieties of crops and hybrid seeds.
In simple words: Molecular probes are like tiny detectors made of DNA or RNA. They are important because they help find specific genes in research, detect bad substances in food, solve family mysteries, and improve crops.

🎯 Exam Tip: Define molecular probes clearly as labeled DNA/RNA segments and emphasize their role in specific sequence detection via hybridization. When discussing their utility, provide diverse examples from research, environmental monitoring, forensics, and agriculture to show a broad understanding of their applications.

 

Question 5. Write an essay on the importance of genetic engineering.
Answer: Scientists working in biotechnology have achieved many useful results. These achievements have brought significant benefits to medical science, agriculture, and various industries. Through genetic engineering, it has become possible to improve crop varieties, domestic animals, and the quality of industrial products. Genetic engineering is now considered a very important field of biology.
Some important achievements include:
• Cloning of the Nitrogen fixation (Nif) gene in cereal crops.
• Cloning of the Haemophilic gene.
• Cloning of the Hepatitis B virus gene.
• Cloning of the Human growth hormone and insulin gene.
• Cloning of penicillin G acylase gene for producing penicillin.
• Work on the Human Genome Project.
In simple words: Genetic engineering is very important because it helps scientists make big improvements in medicine, farming, and industry. It lets us create better crops, healthier animals, and new medicines by changing genes, showing its huge impact on many parts of life.

🎯 Exam Tip: When writing about the importance of genetic engineering, ensure you cover its applications across different sectors like health (insulin, vaccines), agriculture (crop improvement), and research (Human Genome Project), demonstrating a comprehensive understanding of its impact.