Isolation of Genomic DNA from Plant Material (Banana/Papaya)
What you will learn
Extract and isolate genomic DNA from ripe banana or papaya fruit tissue through mechanical disruption, detergent cell lysis, protein digestion, and ice-cold ethanol spooling.
Materials needed
- Ripe Banana / Papaya / Green Peas gWhat is it?Ripe Banana / Papaya / Green Peas g₹50
DNA Extraction Lysis Buffer: 10% SDS / dishwashing liquid, 2M Sodium Chloride (NaCl) in distilled water.
Specifications- Buffer Formula
- 50 mL liquid detergent + 15 g non-iodized NaCl in 450 mL H2O
- Function
- Membrane lipid solubilization and DNA phosphate charge neutralization
- Lysis Buffer: Liquid Dishwashing Detergent (10 mL) + Non-iodized Table Salt (3 g) + Distilled Water (90 mL) mLWhat is it?Lysis Buffer: Liquid Dishwashing Detergent (10 mL) + Non-iodized Table Salt (3 g) + Distilled Water (90 mL) mL₹95
Ice-cold 95% Ethanol or Isopropanol chilled to -20°C in laboratory freezer.
Specifications- Grade
- Molecular biology / Analytical grade 95%
- Temperature
- -20 °C chilled prior to experiment
- Volume
- 200 mL
- Ice-cold 95% Ethanol or Isopropanol (stored at -20°C) mLWhat is it?Ice-cold 95% Ethanol or Isopropanol (stored at -20°C) mL₹140
Ripe Banana (Musa acuminata - triploid genome) or ripe Papaya fruit pulp.
Specifications- Tissue Type
- Triploid/Octoploid high-copy plant tissue rich in DNA
- Enzyme Source
- Fresh pineapple juice (bromelain protease)
- Mortar and Pestle / Zip-lock bagWhat is it?Mortar and Pestle / Zip-lock bag₹185
Standard laboratory apparatus used in Isolation of Genomic DNA from Plant Material (Banana/Papaya).
Specifications- Category
- Biology Apparatus
- Grade
- CBSE / NEP 2020 Laboratory Standard
- Meat tenderizer / Papain / Pineapple juice (protease source) mLWhat is it?Meat tenderizer / Papain / Pineapple juice (protease source) mL₹230
Standard laboratory apparatus used in Isolation of Genomic DNA from Plant Material (Banana/Papaya).
Specifications- Category
- Biology Apparatus
- Grade
- CBSE / NEP 2020 Laboratory Standard
- Cheesecloth / Fine tea strainerWhat is it?Cheesecloth / Fine tea strainer₹275
Standard laboratory apparatus used in Isolation of Genomic DNA from Plant Material (Banana/Papaya).
Specifications- Category
- Biology Apparatus
- Grade
- CBSE / NEP 2020 Laboratory Standard
- Test tubes and Glass Spooling Rod setWhat is it?Test tubes and Glass Spooling Rod set₹320
Standard laboratory apparatus used in Isolation of Genomic DNA from Plant Material (Banana/Papaya).
Specifications- Category
- Biology Apparatus
- Grade
- CBSE / NEP 2020 Laboratory Standard
Tick items as you collect them. Tap + to see the product, specifications and buy options.
Stay safe
- Ethanol must be ice-cold (-20°C freezer chilled); warm ethanol will not precipitate DNA effectively.
- Pour ethanol very slowly along the tube side to form two distinct stratified layers.
- Do not whip or shake vigorously after adding detergent to prevent shearing long DNA strands into fragments.
- Use fresh fruit for highest nucleic acid yield.
Steps
- 1Mash 50 g of peeled banana thoroughly in a zip-lock bag or mortar to break down plant cell walls mechanically.Observation
Peel ripe banana; weigh 20 g and mash thoroughly in mortar with 50 mL extraction buffer (detergent + salt).
SafetyMash gently to avoid excessive foaming.
- 2Add 50 mL of prepared lysis buffer (detergent disrupts phospholipid cell and nuclear membranes; salt shields negatively charged phosphate DNA backbones).Observation
Incubate banana slurry in 60°C water bath for 15 minutes to facilitate cell lysis and inactivate endogenous DNases.
SafetyDo not exceed 60°C to prevent thermal denaturation of genomic DNA strands.
- 3Mix gently for 10 minutes to avoid excess froth formation.Observation
Cool mixture in ice bath for 5 minutes; filter through cheesecloth into clean beaker to remove fibrous cell debris.
SafetyDo not squeeze cheesecloth forcefully to avoid pushing particulate starch into filtrate.
- 4Filter the homogenate through double-layered cheesecloth into a clean beaker to collect cellular filtrate.Observation
Add 5 mL fresh pineapple juice (bromelain enzyme); swirl gently and incubate 5 minutes to digest histone proteins.
SafetySwirl gently; vigorous shaking causes mechanical shear breaking DNA into tiny fragments.
- 5Add 5 mL pineapple juice or meat tenderizer (proteases digest histones and cellular proteins associated with DNA) and swirl for 5 minutes.Observation
Tilt beaker at 45°; slowly pour 30 mL ice-cold 95% ethanol down the inside wall to form a distinct clear upper layer.
SafetyEthanol must be ice-cold (-20°C freezer) for rapid precipitation; pour very slowly to avoid mixing layers.
- 6Tilt a test tube containing 10 mL filtrate at a 45° angle. Slowly trickle 10 mL of ice-cold ethanol down the tube wall to form an unmixed top layer.Observation
Watch translucent white cottony fibers of DNA precipitate at interface; twirl glass rod to spool intact DNA threads.
SafetyLift spooled DNA gently and transfer into microcentrifuge tube containing 70% ethanol.
- 7Watch white translucent mucous-like DNA precipitate at the water-alcohol interface. Spool the DNA fibers onto a clean glass rod by rotating gently.
Tap + on a step to see what you will observe and any safety tips.
Record your observations
| Isolation Protocol Step | Reagent Added & Action | Visual Observation | Biological Mechanism |
|---|---|---|---|
| Mechanical Maceration | Mortar and pestle grinding | Homogeneous yellow fruit pulp | Breaks rigid plant cellulose cell walls |
| Cell Lysis | Detergent + Salt extraction buffer (60°C) | Viscous foaming suspension | SDS detergent dissolves lipid bilayer membranes; salt shields phosphate backbone |
| Protease Digestion | Meat tenderizer / Papain / Pineapple juice | Reduced slurry viscosity | Enzymatic cleavage of histone proteins packaging chromatin |
| Cold Ethanol Precipitation | Ice-cold 95% ethanol layered slowly | Cloudy white mucous-like precipitates at interface | DNA is completely insoluble in cold ethanol; precipitates instantly |
| Glass Rod Spooling | Twirling glass rod at interface | Fibrous translucent white threads spooling around rod | High-molecular-weight genomic DNA strands wound into visible spool |
Tap a highlighted cell to write your own observation.
Result and conclusion
Visible white fibrous threads of aggregated genomic DNA precipitated at the ice-cold alcohol interface and successfully spooled onto a clean glass rod.
| Observation | What it means |
|---|---|
| Detergent Membrane Solubilization | Liquid detergent amphiphilic molecules break apart the phospholipid bilayer of plasma membrane and nuclear envelope. |
| Sodium Ion Charge Shielding | NaCl provides Na⁺ cations that neutralize negative charges on DNA phosphate backbones, allowing strands to aggregate. |
| Differential Ethanol Solubility | DNA is soluble in polar water but completely insoluble in cold ethanol; low dielectric constant triggers precipitation. |
| Macromolecular Fiber Spooling | Long intact genomic DNA double helices tangle together, forming spooled fibrous white threads visible to naked eye. |
Sample readings. Replace with your own results.