RBSE Solutions Class 12 Biology Chapter 16 Plant Tissue Culture

RBSE Class 12 Biology Chapter 16 Multiple Choice Questions

Question 1. Who is the credited for producing haploid plants from anther lobe culture?
(a) Johari and Maheshwari
(b) Haberlandt
(c) P.R. White
(d) Guha and Maheshwari
Answer: (d) Guha and Maheshwari
In simple words: Guha and Maheshwari were the scientists who first successfully grew haploid plants from a part of the flower called the anther lobe. This was an important step in plant tissue culture.

🎯 Exam Tip: Remember key scientists and their specific contributions in plant tissue culture, as these are common factual questions.

Question 2. Disease-free plants are obtained from virus-infected plant by?
(a) Embryo culture
Answer: (a) Embryo culture
In simple words: Even if a plant has a virus, the tiny embryo inside its seed is often free of the virus. So, growing new plants from these embryos can give you healthy, disease-free plants.

🎯 Exam Tip: Focus on techniques used to produce healthy plants from diseased ones, as this highlights practical applications of tissue culture.

Question 3. Who is known as the father of Plant Tissue culture?
(a) Robert Hooke
(b) Haberlandt
(c) Steward
(d) Cocking
Answer: (b) Haberlandt
In simple words: Haberlandt is known as the father of plant tissue culture because he was the first to propose the idea of culturing plant cells outside a plant body.

🎯 Exam Tip: Knowing the pioneers in any scientific field helps in understanding the historical development and foundational concepts.

Question 4. Ti plasmid is found in?
(a) A.tumefaciens
(b) A. rhi-bogenes
(c) E.coli
(d) Bacillus thermogenesis
Answer: (a) A.tumefaciens
In simple words: The Ti plasmid is a special piece of DNA found in a type of bacteria called Agrobacterium tumefaciens. This plasmid helps in transferring genes to plants.

🎯 Exam Tip: Understand the role of Ti plasmid as a natural vector in genetic engineering, especially its association with Agrobacterium tumefaciens.

Question 5. Who is credited for obtaining Protoplast by enzymatic degradation of Plant cell wall?
(a) T. Murashige
(b) E.Ball
(c) F.W. Went
(d) E.C. Cocking
Answer: (d) E.C. Cocking
In simple words: E.C. Cocking was the scientist who successfully removed the cell wall from plant cells using enzymes to get protoplasts.

🎯 Exam Tip: Recall the names of scientists associated with specific groundbreaking techniques in plant biotechnology, such as protoplast isolation.

Question 6. For triploid culture in plants, which is taken as explant?
(a) Apical Meristematic tip
(b) Embryo
Answer: (b) Embryo
In simple words: To grow plants with three sets of chromosomes (triploid), the embryo is commonly used as the starting material in tissue culture.

🎯 Exam Tip: Match the type of culture (e.g., haploid, triploid) with the most appropriate explant material. Embryos are often used for specific ploidy levels.

Question 7. Indirect gene transfer is done in plants by?
(a) Gene gun
(b) Electroporation
(c) Microinjection
(d) Agrobacterium
Answer: (d) Agrobacterium
In simple words: When genes are moved into plants indirectly, a special helper like Agrobacterium bacteria is often used. It acts like a natural delivery system.

🎯 Exam Tip: Distinguish between direct (e.g., gene gun, microinjection) and indirect (e.g., Agrobacterium-mediated) methods of gene transfer in plants.

Question 8. Insect-resistant Bt gene is found in which of the following?
(a) Bacillus subtilis
(b) Bacillus thermogenesis
(c) Bacillus anthracis
(d) Pseudomonas citrus
Answer: (b) Bacillus thermogenesis
In simple words: The special gene that makes plants resistant to insects, called the Bt gene, comes from the Bacillus thermogenesis bacterium.

🎯 Exam Tip: Remember the specific bacterial origin of the Bt gene, as it's a fundamental concept in transgenic crops.

Question 9. For which characteristic, a gene was transferred in "Golden rice"?
(a) Vitamin A
(b) Vitamin C
(c) Vitamin D
(d) Vitamin B
Answer: (a) Vitamin A
In simple words: Golden rice was specially made to have more Vitamin A, which is a key nutrient for good health.

🎯 Exam Tip: Golden Rice is a classic example of genetically modified crops; know its specific modification and purpose.

Question 10. A special feature of “Flavr-Savr” tomatoes is?
(a) Drought resistant
(b) High salinity resistant
(c) Strong fruit wall
(d) Killer cotton
Answer: (c) Strong fruit wall
In simple words: Flavr-Savr tomatoes were engineered to have a stronger fruit wall, meaning they stayed firm and fresh for longer.

🎯 Exam Tip: Recognize "Flavr-Savr" tomatoes as an early example of genetically engineered food and remember their primary improved characteristic.

Question 10. Bt gene containing cotton is called?
(a) Aseptic cotton
(b) Romil cotton
(c) Golden cotton
(d) Killer cotton
Answer: (d) Killer cotton
In simple words: Cotton plants that have the special Bt gene are often called killer cotton because this gene helps them fight off pests on their own.

🎯 Exam Tip: Link specific modified crops (like Bt cotton) to their characteristic names and the genes they contain.

RBSE Class 12 Biology Chapter 16 Very Short Answer Questions

Question 1. Define totipotency.
Answer: Totipotency is the special ability of a plant cell to grow and develop into a complete, new plant. Because of this property, we can grow an entire plant from just a small piece of tissue using tissue culture.
In simple words: Totipotency is when a single plant cell can grow into a whole new plant.

🎯 Exam Tip: Clearly define totipotency and mention its significance in plant tissue culture to score full marks.

Question 2. What is an artificial seed?
Answer: An artificial seed is like a fake seed made in a lab. It is a somatic embryo (a plant embryo grown from body cells) that is covered or encapsulated, usually with calcium alginate beads, or simply dried out. These artificial seeds allow us to produce new plants from somatic embryos in a protected way.
In simple words: An artificial seed is a lab-made seed using a plant embryo, often covered in a protective layer.

🎯 Exam Tip: Describe both the composition (encapsulated somatic embryo) and the protective mechanisms (calcium alginate/desiccation) of artificial seeds.

Question 3. What is callus?
Answer: Callus is an unorganized group of cells that grows from plant cells placed in a special culture. These cells are typically parenchymatous, meaning they are basic, simple plant cells.
In simple words: Callus is a lump of unorganized plant cells that grows in tissue culture.

🎯 Exam Tip: Explain callus as an undifferentiated mass of cells and mention its origin from meristematic cells in culture.

Question 4. What is the importance of haploid plant production?
Answer: Haploid plant production is very important for plant breeding and genetic studies. Haploid plants have only one set of chromosomes, which makes it easier for scientists to see and study new genetic traits that might otherwise be hidden by a second set of chromosomes. This helps in quickly developing new and improved plant varieties.
In simple words: Making haploid plants helps scientists study genes easily and create new plant types faster.

🎯 Exam Tip: Highlight the benefits of haploids in genetic analysis and accelerated breeding programs due to the expression of recessive traits.

Question 5. What are the different types of nutrient media used in tissue culture?
Answer: In plant tissue culture, several types of nutrient media are used. Some well-known ones are White's medium (developed in 1953), Gamborg et al. medium (1968), and M.S. medium (1962). Among these, M.S. medium, also known as Murashige and Skoog medium, is the most commonly used for growing plant tissues in experiments.
In simple words: Different nutrient mixes are used, but M.S. medium is most popular for growing plant tissues.

🎯 Exam Tip: Name a few common culture media, emphasizing the widely used MS (Murashige and Skoog) medium and its significance.

Question 6. What do you understand by micropropagation?
Answer: Micropropagation is a modern way to quickly multiply plants using tissue culture. This method helps to produce many new plants from a small piece of a parent plant. It is used commercially to grow many similar plants in a small area and in a short amount of time, especially for new or special plant types.
In simple words: Micropropagation quickly makes many new plants from a small piece using tissue culture.

🎯 Exam Tip: Define micropropagation as rapid multiplication via tissue culture and explain its commercial benefits like producing many identical plants quickly.

Question 7. Write the names of any three methods of direct gene transfer.
Answer: Three methods of direct gene transfer are:
• Gene gun method
• Electroporation
• Lipofection
• Microinjection
In simple words: Gene gun, electroporation, and microinjection are ways to put new genes directly into plant cells.

🎯 Exam Tip: List common direct gene transfer methods; understanding how they work without a biological vector is key.

Question 8. What do you understand by indirect gene transfer?
Answer: Indirect gene transfer is a method where a desired gene is moved into a target plant with the help of a biological vector, usually a bacterium like Agrobacterium. The gene is first inserted into the vector, and then the vector carries it into the plant's cells. This makes the transfer happen indirectly.
In simple words: Indirect gene transfer uses a living helper, like a bacteria, to carry a new gene into a plant.

🎯 Exam Tip: Explain indirect gene transfer by highlighting the use of a biological vector (e.g., Agrobacterium) as an intermediate carrier.

Question 10. Define the following:
1. Culture medium
2. Protoplast
3. Explant
4. Transgenic plant
Answer:
1. Culture medium: This is a special nutrient-rich liquid or gel with a known chemical mix. It is used to grow plant tissues or cells outside the plant in a lab setting.
2. Protoplast: A protoplast is a plant cell that has had its cell wall completely removed. It contains all the cell's living parts but no rigid outer wall.
3. Explant: An explant is any small part of a plant, like a piece of root, stem, leaf, or flower, that is used to start a new tissue culture.
4. Transgenic plant: A transgenic plant is a genetically modified plant. It has new desired features because genes from another source have been added to its own DNA using genetic engineering.
In simple words: A culture medium feeds growing plant cells, a protoplast is a plant cell without a wall, an explant is a plant piece used for growing, and a transgenic plant has added genes.

🎯 Exam Tip: Provide clear, concise definitions for each term, emphasizing the key characteristic or function for each.

RBSE Class 12 Biology Chapter 16 Short Answer Questions

Question 1. Explain microinjection technique of gene transfer.
Answer: Microinjection is a gene transfer method where desired genes are directly put into plant protoplasts (cells without walls) or intact cells. This is done using a very fine glass needle, about 0.5 to 1.0 mm wide, which injects the genes straight into the cytoplasm or nucleus of the cells. This method is especially good for transferring genes into isolated protoplasts.
In simple words: Microinjection uses a tiny glass needle to directly inject genes into plant cells or protoplasts.

🎯 Exam Tip: Describe microinjection by detailing the tool (glass needle), target (protoplast/cell), and direct mechanism of gene insertion.

Question 2. Write a note on any two insect-resistant plants.
Answer: Many important crop plants are often harmed by insects. Bacillus thermogenesis, or Bt for short, is a bacterium known to cause the death of certain insect larvae, like those of the Bollworm. This bacterium has a special gene, called a cry gene, which produces a protein that is toxic to insect pests. This cry gene can be taken from the Bt bacterium and put into cotton plants. The cotton plant with this gene is called Bt cotton or killer cotton, and it becomes resistant to the Bollworm. This means the cotton plant can protect itself from insect attacks.
In simple words: Bt cotton is an insect-resistant plant. It has a gene from a bacterium that makes a protein to kill pests like the Bollworm, protecting the crop naturally.

🎯 Exam Tip: Explain Bt cotton, detailing its origin (Bacillus thermogenesis), the gene involved (cry gene), and the mechanism of insect resistance (toxic protein).

Question 3. Write a note on the steps of tissue culture.
Answer: The tissue culture process involves several key steps:
1. Selection of explant and pretreatment: First, a suitable plant part (explant) is chosen based on the experiment's goal. For example, meristematic tips are used for virus-free plants. This explant is then washed with running water and a chemical like Tween-20 to remove dirt and microbes from its surface. This cleaning is called pretreatment.
2. Surface Sterilization of explant: After pretreatment, the explant is sterilized to remove all microbes from its surface. This is done using appropriate disinfectant chemicals, such as Mercuric chloride or ethanol, under sterile conditions in a laminar airflow chamber. The choice of disinfectant depends on the type of explant.
In simple words: Tissue culture starts by picking a plant piece and washing it, then making sure its surface is completely clean of germs.

🎯 Exam Tip: For tissue culture steps, always begin with proper explant selection and meticulous sterilization; these are fundamental for successful culture.

Question 4. Differentiate between a normal embryo and somatic embryo?
Answer: Normal embryo and somatic embryo are different in their origin and ploidy level.
A normal embryo forms from the fusion of male and female reproductive cells (gametes), creating a zygote. This embryo is diploid, meaning it has two sets of chromosomes.
A somatic embryo develops from non-reproductive plant cells (somatic cells). It can be haploid (one set of chromosomes) or diploid (two sets) depending on the somatic cells it came from. Growing plants from these somatic embryos is called somatic embryogenesis.
In simple words: A normal embryo comes from seed fertilization and has two sets of genes, while a somatic embryo grows from regular plant cells and can have one or two sets of genes.

🎯 Exam Tip: Clearly state the origin (zygote vs. somatic cells) and typical ploidy (diploid vs. variable) to differentiate between normal and somatic embryos.

Question 5. Describe the method of micropropagation and its significance.
Answer: Micropropagation is a technique that uses plant tissue culture to rapidly produce a large number of plants. In this method, small plantlets are grown from a callus (an unorganized mass of cells). Once developed, these plantlets are transferred to natural conditions after a period of hardening and getting used to the environment (acclimatization). This technique is very important for growing many commercially valuable plants, like orchids (e.g., Cattleya, Cymbidium) and ornamental plants (e.g., Gerbera, Carnation). Many research places use micropropagation to quickly multiply important forest and garden plants.
In simple words: Micropropagation quickly makes many plants from small pieces using tissue culture, helping to grow valuable plants for business and research.

🎯 Exam Tip: When explaining micropropagation, mention the steps from callus to plantlets, acclimatization, and its commercial importance for rapid, large-scale plant multiplication.

Question 6. What is embryo rescue technique? Write its importance.
Answer: The embryo rescue technique is used when plants from different species or genera are crossed, and their hybrid seeds often fail to develop properly due to problems with the endosperm (food source for the embryo). This leads to the early death of the hybrid embryo and sterile seeds. In embryo rescue, the hybrid embryo is carefully removed from such a sterile seed at the right time and grown on a special nutrient medium in a lab. This allows scientists to create new hybrid plants that would otherwise not be possible. It has been used to produce many useful hybrids in various crops.
In simple words: Embryo rescue saves hybrid plant embryos from dying in crosses between different plants, growing them in a lab to make new plants.

🎯 Exam Tip: Define embryo rescue by explaining the problem (premature embryo death in wide crosses) and the solution (in vitro culture) to create novel hybrids.

Question 8. What do you understand by tissue culture?
Answer: Tissue culture is a modern technique where plant protoplasts, cells, tissues, organs, or even entire small plant systems are grown in a sterile environment on a chemically defined nutrient medium. This technique allows for the regeneration and rapid multiplication of commercially important plants in a small space and short time. It is a main tool in biotechnology, widely used for developing genetically modified or transgenic plants.
In simple words: Tissue culture is a lab method to grow plant parts like cells or tissues in a special feeding liquid to make new plants or genetically modified plants.

🎯 Exam Tip: Include the key aspects of tissue culture: aseptic conditions, chemically defined medium, totipotency, and its applications in plant regeneration and genetic engineering.

RBSE Class 12 Biology Chapter 16 Essay Type Questions

Question 1. Write a brief note on the history of tissue culture.
Answer: Plant tissue culture was first successfully carried out by Gottlieb Haberlandt in 1902. This marked the beginning of growing plant cells in a sterile environment. Many scientists have since expanded on this field, and today, tissue culture is widely used to regenerate commercially useful new plants and create transgenic plants. The modern cell theory states:
• A cell is the basic structural, functional, and fundamental unit of life.
• New cells come from existing cells.
• All metabolic reactions happen inside the cell.
• Genetic information passes from one generation to the next through cells.
Haberlandt's work in 1902 experimentally proved that plant cells have totipotency. Unlike most animal cells, plant cells can differentiate and regenerate a whole plant. Tissue culture is the process of growing plant protoplast, cells, tissue, organs, or entire systems in a controlled, sterile environment using a known chemical medium.
Plant tissue culture was pioneered by German scientist Gottlieb Haberlandt in 1902. Many scientists have since made important contributions. For example, W.J. Robbins and W.Kotte (1922) cultured plant root and shoot tips. F.W. Went (1926) discovered growth hormones like auxin. R.J. Gautheret, P.R. White, and P. Nobecourt (1939) established cultures that could grow for a long time. Van Overbeek (1941) used coconut milk in culture medium for cell division. E. Ball (1946) developed clones of whole plants from apical meristems. F. Skoog and Miller (1955) found that Kinetin hormone helps in cell division in tissue culture. E.C. Cocking (1960) separated protoplasts using enzymes. T. Murashige and F. Skoog (1962) developed the most widely used MS medium. S. Guha, Mukherjee, and S.C. Maheshwari (1964) first produced haploid plants from pollen grains.
In simple words: Plant tissue culture started with Haberlandt in 1902. Many scientists then helped improve it, discovering hormones and developing methods like MS medium, making it a key tool for growing and changing plants today.

🎯 Exam Tip: When discussing the history, always start with Haberlandt and his concept of totipotency. Mentioning a few key scientists and their specific contributions, such as MS medium or haploid plant production, will demonstrate comprehensive knowledge.

Question 2. What are Transgenic plants? How these are developed? Write their importance.
Answer: Genetically Modified Plants Or Transgenic Plants:
Transgenic plants are genetically engineered plants. They are created by adding new desired qualities through recombinant DNA techniques. Over the past few decades, many transgenic dicot and monocot plants have been developed and are being tested in crop fields. The process to develop transgenic plants involves several steps:
• Identifying and isolating the gene with the desired feature.
• Creating a recombinant plasmid (a circular DNA molecule) and transforming it into Agrobacterium bacteria.
• Transferring this transformed Agrobacterium into the cells of the target plant.
• Selecting the plant cells that have successfully received the new gene, culturing them, and regenerating a new plant.
• Ensuring the desired gene expresses itself in the developed transgenic plants.
Importance of Transgenic plants:
As Bioreactors:
Genetically modified plants are used as bioreactors because plants act like natural chemical factories. They can produce many types of chemical compounds using sunlight as their energy source. By adding desired genes, plants can be made to produce valuable compounds like amino acids, proteins, vitamins, pharmaceutical products, and enzymes, which are useful in food and medicine. This is why biotechnology in this context is sometimes called molecular farming.
Some examples of plants developed for molecular farming include:
• "Golden Rice" (enriched with Vitamin A).
• Super Potato.
• Improved seed protein quality.
• Edible vaccines.
• Important medicines.
• Biodegradable Plastic.
• Genetically engineered metabolism.
In simple words: Transgenic plants are modified plants with new genes. They are made by putting desired genes into plants to give them new traits. These plants are important as they can act like tiny factories, producing useful chemicals and improving crops, such as Golden Rice with added Vitamin A.

🎯 Exam Tip: Define transgenic plants and outline the main steps of their development. Emphasize their importance as bioreactors and list concrete examples like Golden Rice and edible vaccines.

Vector-Mediated or Indirect Gene Transfer Methods

Indirect gene transfer involves using a vector to carry desirable genes into plant cells. This process has three main methods:

1. Agrobacterium-mediated Gene Transfer:
Answer: The Ti-plasmid from Agrobacterium tumefaciens is widely used for plant transformation. This bacterium has a large plasmid called Ti-plasmid (tumor-inducing plasmid). A part of this plasmid, known as T-DNA (transferred DNA), gets transferred to the plant genome in infected cells, causing plant tumors (crown galls). This shows that A. tumefaciens naturally transfers T-DNA from its plasmid into the plant's chromosomes at the infection site. Because of this unique ability, the bacterium is known as a "natural genetic engineer of plants." Ti-plasmid can be used as a vector to insert useful foreign genes into plant cells and tissues. The foreign genes (transgenes), such as those for insect resistance (e.g., Bt gene) and plant selection marker genes (like antibiotic genes that provide resistance to kanamycin), are cloned into the T-DNA region of the Ti plasmid. Since the Ti plasmid can cause tumors, the tumor-inducing gene (T-DNA) is removed from the Agrobacterium plasmid DNA and replaced with the desired gene. This modified Agrobacterium, containing the desired gene, is then cultured with plant tissues for transfer. Typically, rings or discs of leaves from plants like tomato, tobacco, Petunia, and rose are used. These release acetosyringone, which activates the Ti plasmid operons. When these operons are activated, the desired gene-containing Ti plasmid enters plant cells and integrates into their genome. After 2-3 days of combined culture, the transformed cells are grown in a suitable medium. This technique mainly works for dicotyledonous plants. Before the 20th century, Agrobacterium tumefaciens was seen only as a cause of plant diseases. However, its ability to transfer foreign DNA made it valuable in genetic engineering, and it is now known as a Natural Genetic Engineer.
In various research institutes, scientists use the Ti plasmid as a vector. By inserting desired genes into T-DNA, they can introduce many important traits into plants, such as herbicide tolerance, pathogen tolerance, stress tolerance, increased nutritional value (like Vitamin A in golden rice), and improved nitrogen fixation. While Agrobacterium typically doesn't infect monocot plants, Japanese scientists in 1994 successfully used the Ti plasmid to transform rice.
In simple words: Agrobacterium bacteria, with its special Ti-plasmid, acts like a natural delivery truck to put new genes into plants, especially dicots. This helps make plants better in many ways, like making them resistant to pests or improving their nutrition.

🎯 Exam Tip: Explain the key role of Agrobacterium's Ti-plasmid as a natural vector. Describe how the tumor-inducing gene is replaced with a desired gene and its application in creating transgenic plants.

2. Virus Mediated Gene Transfer:
Answer: Both DNA and RNA viruses can act as excellent vectors for transferring desired genes. Two important groups of DNA viruses, Caulimoviruses and Geminiviruses, are commonly used for gene transfer. Retroviruses, Lentiviruses, and Adenoviruses are also widely used in genetic engineering for gene transfer.
In simple words: Viruses, both DNA and RNA types, can be used to carry new genes into cells. Caulimoviruses and Geminiviruses are popular for this job.

🎯 Exam Tip: Mention the specific virus types (DNA and RNA) used as vectors and give examples like Caulimoviruses or Geminiviruses.

3. In-planta method:
Answer: This gene transfer technique was developed by Failzadman and Markakes (1987). In this method, Arabidopsis seeds were genetically modified using Agrobacterium and then grown into plants. The transformed plants were identified by germinating the seeds on an antibiotic-free medium. Similarly, the apical meristematic part of germinated seed embryos can be infected with Agrobacterium to produce genetically modified plants. This technique directly transfers genes into the plant, hence it is called the "in planta" technique.
In simple words: The in-planta method directly changes plant genes by using Agrobacterium to infect seeds or embryos, then growing them to find the modified plants.

🎯 Exam Tip: Describe the in-planta method as a direct approach where Agrobacterium infects seeds/embryos to produce modified plants, avoiding tissue culture steps.

Direct Gene Transfer Methods

In this method, the DNA of the desired gene(s) is transferred directly using various techniques without needing a biological vector. While Agrobacterium-mediated gene transfer is mainly for dicotyledons, direct gene transfer methods are often used for monocotyledons, especially important cereals where agroinfection is not usually possible. These techniques aim to improve plants and add desired features without biological vectors.

1. Chemical methods of Gene Transfer:
Answer: In this method, plasmid DNA is first mixed with protoplasts. Then, 15-25% PEG (polyethylene glycol) is added. This PEG helps the protoplasts take up the DNA. The transformed protoplasts are then cultured on a special medium, and those that have successfully taken up the DNA are selected using marker genes. Other substances like liposomes, diethyl aminoethyl (DEAE), and dextran proteins are also used for gene transfer in plants and animals. PEG-directed gene transfer is considered safe for protoplasts.
In simple words: Chemical methods use substances like PEG to help plant protoplasts directly take in new DNA, which then helps select the changed cells.

🎯 Exam Tip: Explain the role of PEG in promoting DNA uptake by protoplasts in chemical gene transfer methods, and briefly mention other chemical agents.

2. Physical methods of Gene Transfer:
Answer: Direct gene transfer in plants can also be done effectively using several physical methods. Some main physical methods are as follows:
1. Gene gun: The gene gun, also called a particle gun or microprojectile, allows gene transfer into intact plant cells (even those with a cell wall). In this process, tiny gold or tungsten particles (1-3 mm in diameter) are coated with the desired DNA. These microparticles are then shot (bombarded) into the target cells. The particles penetrate the cell wall and enter the cell, where the desired DNA integrates with the host cell DNA, forming transgenic DNA. This technique was first used by Klein and Co-workers (1987) in onion cells to transfer DNA and viral RNA.
In simple words: Physical gene transfer methods use tools like a gene gun to shoot DNA-coated particles directly into plant cells. This lets the new DNA enter the cell and become part of the plant's own DNA.

🎯 Exam Tip: Focus on describing the mechanism of the gene gun, including the DNA-coated particles (gold/tungsten) and how they penetrate plant cells.

Question 4. Describe in brief various steps of tissue culture.
Answer: Tissue culture involves several steps to grow a complete plant from a small part of a plant. Here are the main steps:
Various Steps Of Tissue Culture:
The micropropagation method uses these steps to grow a full plant from a selected part of the plant.
Zero Step: This step has two parts:
1. Selection of Explant and Pretreatment: First, you choose a small piece of the plant, called an explant. The choice of explant depends on what you want to achieve in your experiment. For different goals, specific explants are used (see table below). Before sterilizing, the explants are washed under running water with a chemical called Tween-20. This removes dust and microbes from the surface. This cleaning is called pretreatment. Afterwards, the explants are moved to a culture room, where either callus (unorganized cell mass) or organs begin to form.

🎯 Exam Tip: Remember to clearly outline each step in chronological order and explain its purpose to score well on descriptive questions about tissue culture.

Question 5. Write an illustrated account of physical methods of gene transfer.
Answer: Physical methods of gene transfer involve moving DNA into plant cells without using biological vectors. These methods are important for genetic engineering. Here are the main physical methods:
1. Gene gun method
2. Electroporation
3. Lipofection or Liposome mediated gene transfer
4. Microinjection

1. Gene gun: This method is also called a particle gun or shotgun method. It allows gene transfer into whole, intact plant cells that still have their cell walls. This technique was first developed by Klein and his colleagues in 1987. They used it to transfer DNA and viral RNA into onion cells. In this process, tiny gold or tungsten particles, 1-3 mm in diameter, are coated with the desired DNA. These microparticles are then shot (bombarded) into the target cells using a microprojectile device. The DNA-coated particles go through the cell wall and enter the cell. Inside the cell, the desired DNA combines with the host cell's DNA, creating transgenic DNA.
2. Electroporation: In this method, the target cells, protoplasts, or tissues are exposed to a short pulse of high voltage electricity. This creates tiny, temporary pores in the cell membrane (plasmalemma). The desired DNA is present in a solution around the cells. Through these pores, the DNA enters the cells and then gets incorporated into the cell's genetic material. This method is widely used for transferring genes into monocotyledonous plant cells.
3. Liposome mediated gene transfer: In this technique, genes are transferred using spherical lipid molecules called liposomes. These liposomes are filled with the desired DNA and water. First, these lipid capsules, containing DNA, attach to the cell membrane (plasmalemma) and then merge with it. The DNA from the liposomes then enters the cell and moves into the nucleus, where it becomes part of the host cell's genome. This liposome-directed gene transfer method, also known as lipofection, is very effective for transferring genes into bacteria, animal, and plant cells.
4. Microinjection: This method involves injecting genes directly into plant protoplasts or cells. A very fine glass needle, about 0.5 to 1.0 mm in diameter, or a micropipette is used to deliver the genes directly into the cytoplasm or nucleus of the cells. This technique is particularly suitable for transferring genes into isolated protoplasts.
Other methods like Ladder-dependent gene transfer and Silicon carbide fiber-dependent gene transfer are also used.
In simple words: Physical gene transfer methods directly push new DNA into plant cells using tools like a gene gun (shooting DNA-coated particles), electroporation (using electric pulses to make temporary holes), liposomes (lipid balls carrying DNA), or microinjection (using tiny needles). This helps create genetically modified plants.

🎯 Exam Tip: When describing physical gene transfer methods, clearly name each technique and explain how it physically delivers DNA into the target plant cell, including any specific tools or conditions used.

Question 6. Describe different steps of micropropagation.
Answer: Micropropagation is a technique used to quickly multiply plants using tissue culture. It involves several key steps to grow a complete plant from a small explant.
Micropropagation:
The following steps are used in the micropropagation method, starting from selecting an explant until a complete plant is developed:
Zero Step: This step is divided into two parts:
1. Selection of Explant and Pretreatment: The first step is to choose a suitable explant, which is a small piece of plant material. The choice of explant depends on the specific goals of the experiment. The table below shows suitable explants for different objectives. Before surface sterilization, the chosen explants are washed under running water with a chemical called Tween-20. This cleaning process, known as pretreatment, removes dust and microbes from the explant's surface. After pretreatment, the explant is moved to a culture room where either callus or organ formation begins. The developing plantlets are then carefully transplanted to a greenhouse or field once they are strong enough.

🎯 Exam Tip: When explaining micropropagation, ensure you detail the process from explant selection and preparation to the eventual transfer of plantlets, highlighting how each stage contributes to rapid multiplication.

Question 7. What are the different components of an ideal culture medium? Explain.
Answer: An ideal culture medium must contain all the mineral nutrients necessary for plant growth. The M.S. (Murashige and Skoog) medium, developed in 1962, is the most commonly used culture medium. Its basic components include:
Basic Composition of culture medium:
1. Vitamins: Essential vitamins like B1, B3, B5, and B6 are included to support cell metabolism and growth.
2. Amino acid-Glycine: Glycine is the simplest amino acid and is often added to provide a nitrogen source and promote growth.
3. Complex Nutrients: These include various organic compounds that supply additional nutrients and growth factors:
• Casein hydrolysate
• Coconut milk
• Malt extract
• Tomato juice
• Yeast extract
• Corn milk
4. Phyto hormones: Plant hormones are crucial for regulating growth and differentiation, such as auxins and cytokinins.
5. Auxins - Root Differentiation: Specific auxins are used to encourage root development. Examples include:
• Indole butyric acid
• Naphthalene acetic acid
• Napthoxy acetic acid
In simple words: A perfect plant growth liquid (culture medium) has all the nutrients plants need, like special vitamins (B1, B3), simple amino acids (Glycine), and other complex food sources (like coconut milk). It also includes plant hormones (phytohormones) to help roots and shoots grow properly.

🎯 Exam Tip: When asked about culture medium components, list the main categories (vitamins, amino acids, complex nutrients, hormones) and give specific examples for each to show a comprehensive understanding.