the molecule of life dna l.
Skip this Video
Loading SlideShow in 5 Seconds..
The Molecule of Life: DNA PowerPoint Presentation
Download Presentation
The Molecule of Life: DNA

Loading in 2 Seconds...

play fullscreen
1 / 19

The Molecule of Life: DNA - PowerPoint PPT Presentation

  • Uploaded on

The Molecule of Life: DNA The Molecule of Life: DNA The purpose of this laboratory exercise is to extract and visualize DNA from fruit. The objectives of the laboratory exercise are: To understand where DNA is found To isolate DNA To understand how DNA is extracted

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

The Molecule of Life: DNA

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
the molecule of life dna2
The Molecule of Life: DNA
  • The purpose of this laboratory exercise is to extract and visualize DNA from fruit.
  • The objectives of the laboratory exercise are:

To understand where DNA is found

To isolate DNA

To understand how DNA is extracted

To learn about positive and negative controls


The “rungs” are made up of four bases: A, G, T, C.

Our body is made up of about 100 trillion cells.

That’s 100,000,000,000,000!

Each cell contains the entire human genome.

When unfolded, DNA looks like a double helix: a twisted ladder

Cells differentiate by turning on and off different genes.

DNA is looped and folded so long stretches can be fit into a nucleus

Inside the cell, DNA is found in the nucleus

The DNA is organized into chromosomes: the human genome has 46 chromosomes

Chromosomes have many genes: these are small sections of DNA that code for a particular protein

Adapted from “Journey into DNA”

what does dna look like
What does DNA look like?
  • DNA contains one of four nucleotides: adenine (A), thymine (T), cytosine (C), and guanine (G).
  • A+T or C+G
the role of the nucleotides
The role of the nucleotides
  • The different nucleotides spell out a code: instructions for the cell
  • Each set of instructions is a gene. A gene is a long series of the four letters (nucleotides) that gives instruction to the cell.
lab protocol
Lab Protocol
  • Step 1 – Prepare Materials & Solutions


DNA Buffer: Combine 120 mL of dH2O (distilled water) with 1.5 g salt (noniodized), 5 g baking soda and 5 mL dishwashing liquid.

  • Materials

Ziploc bag Pipet Bulb (3) 10mL Pipettes

Distilled Water Fruit Sample Box of Kimwipes

Buffer Cheesecloth Ethanol (95 – 100 percent)

Test Tube Rack 15 mL conical tubes

Glass rod or wooden stick Metal Spatula

Black paper 50 mL conical tube

Gloves Scissors

Step 2 – Prepare tubes

Label the 15 mL conical tubes with your initials or group name.

Put on your gloves!

  • Step 3 – Prepare Experimental Samples

Weigh out 7.5 g of the fruit from which you will be isolating DNA

In the ziploc bag, combine the fruit with

7 mL of dH2O

3 mL of buffer solution

Grind the mixture into a fine paste.

why do we crush the fruit
Why do we crush the fruit?

So we can break apart and open the cells.

Why do we add buffer solution?

- Detergent breaks open membranes to release DNA

  • Baking soda neutralizes so DNA is not degraded
Filter the mixture through at least two layers of cheesecloth into a 50 ml plastic tube.

Transfer 2 mL of the filtered mixture to the 15ml tube labeled with your initials or group names


Step 4 – DNA Isolation

Add 1 mL of DNA Buffer to the 15 ml tube. Cap and gently invert to mix.

Add 2 mL of ice-cold ethanol slowly down the side of each tube to form a layer that floats on top of each sample.

why add ethanol
Why add ethanol?

Ethanol is less dense than water so it floats on top. All of the proteins we broke up in Step 4 will sink to the bottom; the DNA will float on top.

If there is DNA present in any of the samples it should precipitate out in gray clumps that may look like white fine lint fibers.
  • Use a glass rod to spool out the DNA clumps and place them on black paper for observation.
other ways of visualizing dna
DNA can be run on an agarose gel, which separates DNA pieces based on size. A charge is applied, and because DNA is slightly negatively charged, it will run through the gel towards the positive charge.



Other ways of visualizing DNA

Smaller pieces of DNA can more easily move through the gel and will end up closer to the bottom.

Larger pieces of DNA

Smaller pieces of DNA

other ways of visualizing dna15
Other ways of visualizing DNA

DNA can also be sequenced. These techniques allow us to determine the order of nucleotides (the code).

Being able to “read the code” allows us to identify genes and compare organisms.


Careers in Molecular Biology

Because we inherit genes from our parents, we can use DNA sequences to determine how organisms are related.

Animal breeders use differences in DNA to determine parentage.

Ecologists and conservation biologists use DNA to understand population structure: this can help identify and protect endangered species


Careers in Molecular Biology

Microorganisms can be genetically engineered to produce pharmaceuticals. For example, the human insulin gene is inserted into bacteria to mass produce insulin for diabetics.

Genetic engineers can change gene sequences, or insert new genes to improve organisms.

Genes are inserted into crops to make them mold and pest resistant


Careers in Molecular Biology

Medical professionals and gene therapists use DNA sequences to understand the variation between people in terms of health and disease. This is important in the study of heritable disease (such as breast cancer), organ transplants, and fertility.

Pharmaceutical scientists also use DNA techniques to understand how drugs work in the body, which helps them develop new and better drugs.


Careers in Molecular Biology



Found at the crime scene


There are slight differences in the DNA sequences between different people.

Forensic scientists and crime scene investigators use these differences to help match DNA found at a crime scene to a suspect.