PRACTICAL 7: DNA extraction

BY ELISA OCAMPO AND VIOLETA PALOMO

DNA EXTRACTION

Practical 7

• Beaker
• Funnel
• Test tubes
• Rack
• Filter paper
• Stirring rod
• Spoon
• Methylene blue
• Tweezers

2. Materials and equipment

• Plant tissue (banana)
• Animal tissue (liver)
• Distilled water
• NaCl (table salt)
• Dishwashing detergent
• Alcohol 96º very cold
• Pineaple juice
• Mortar and pestle
• Gracduated cylinder

1. Objectives

• To extract DNA from plants and animal cells, revealing their fibril structure and the degree of DNA packaging in the cell nucleous.

3. Basis

• DNA (more specifically called Deoxyribonucleic acid) is a two-stranded molecule that contains the genetic material that defines all conditions of each living thing. It has a double helix shape, and it's composed of sugar and phosphate groups (adenine (A), cytosine (C), guanine (G) or thymine (T)). The two strands of the helix are connected by chemical bonds.
• DNA is found inside the nucleuos of the cell, in the form of chromatin, joined together by proteins called histones. They are found inside the nucleoplasm and they concentrate in regions, together with proteins and rRNA to codify for the components that make up ribosomes.
• When it has to divide, it condenses in chromosomes and performs the four stages of mitosis: prophase, metaphase, anaphase and telophase.
• In order to carry out this observation of DNA, we need first to extract it. There are three steps to follow: chrushing the leaves, mixing it with detergent and salt, and filtrate the resutl. This all helps to isolate the genetic material so it can be extracted on it's own and then observed carefully under the microscope.
• For DNA to be shown in it's purer form and become isolated, we can use two substances during our experiment: pineapple juice and frozen alcohol.

4. Methodology

• a) Liver / banana DNA extraction
• First, we cut around a bottle cap sized piece of liver or two slices of banana
• We place it in a mortar with a tbs of table salt and 5ml of distilled water
• Smash it until you obtain an homogeneous mixture
• Transfer the mixture into a beaker and add aroun 1 ml (4 drops) of dishwashing detergent, stir slowly, producing as few air bubbles as possible. Let it sit for 5 minutes
• Add between 10ml-20ml of pineapple juice and stir slowly
• Filter the mixture using a funnel and filter paper into a test tube.
• Fill the testube with alcohol more or less till the half. Make sure to pour it with the liquid touching the edges of the test tube to avoid bubbles
• Observe how the DNA floats to the alcohol portion of the test tube
• Pick it up with the tweezers and place it in a microscope slide
• Add one drop of methylene blue and put a coverslip over it
• Observe the results in the microscope.

BANANA DNA

LIVER DNA

5. Results

• What we have observed in the lab; practical script.
• https://www.genome.gov/genetics-glossary/Deoxyribonucleic-Acid
• https://www.msdmanuals.com/es-es/professional/multimedia/figure/estructura-del-dna

7. References

6. Observations

In this practical we observed DNA extractions from both an animal tissue (liver) and plant tissue (banana). The DNA is obtained in form of strands, the best picture to observe them is the bottom left one in the results slide. In that picture we can observe various strands coiled together forming knot like structures