Question

Exercise 1 Extraction of DNA In this exercise, you will extract and observe DNA from split peas. Note: The night before beginning the experiment, place the 91% isopropyl alcohol into a freezer to chill. The entire bottle may be placed in the freezer without harming the bottle or its contents. If a freezer is not available, place alcohol bottle in an ice-bath at least 3 hours before beginning the experiment. Note: If a blender is not available, a mortar and pestie may be used and the split peas must be soaked overnight in distilled water. Procedure 1 Break down the pea tissues with a blender or by hand with a mortar and pestie. Use 1 of the following 2 methods: Blender Method • Retrieve the split peas and 2 salt packets from the kit. • Add the split peas and both salt packets into the blender. • Measure 1 cup of cold water and add it to the blender. . Place the lid onto the blender and blend the split peas, water, and salt mixture on the high setting for approximately 30 seconds.

look over the expeirment instructions in photos 1-3 then answer questions 1-4 in the last photo

Answer 1

Answer 1:

The physical appearance of the DNA:

The precipitated DNA is collected on the top within the alcohol layer, this looks white, long and stringy in appearance. There is a physical force of the clumping DNA together that precipitates and pulls the strands together and helps in rising along with the alcohol.

Answer 2:

The expected experimental results:

If the entire experiment is conducted properly with necessary precautions we will observe and have good results obtained by this methodology.

The DNA must be collected in the topmost layer within the alcohol as stringy, long white colored fragments. They are clumped together due to physical force acting on it. The salty DNA when reacts with the alcohol shows precipitation.

There are certain factors which must be kept in mind while conducting the experiment that can affect the yield obtained by the method, they are:

1. The management of time during the method is important, the detergent must sit for at least 5 minutes. Because this can affect if the cell and nuclear membranes are not properly destroyed or look intact, the DNA collected would not show the same result.
2. Ice cold alcohol used in this is also important as it helps in increasing the yield. Alcohol generally helps in solidifying the DNA and also it can precipitate more quickly by using it.
3. The type of food source used also affects the yield of DNA collected. Often frozen DNA cannot give much amount as it has plenty of water stored in it. So, different sources can yield different amounts of DNA at different rates.

Answer 3 :

The purpose of adding the detergent here is:

Although by blending we separated the pea cells yet the two layers i.e. cell membrane and nuclear membrane still needs to be separated.to achieve this we need detergent. As this opens it up. So, the DNA which is stored inside can come out by breaking the membrane via detergent. Detergent molecules surround the particles of the cell membrane to remove them.

Yes, definitely if detergent is not used in experiment the subsequent steps would not be possible and DNA cannot be collected as we know the cell membranes are made up of lipids that possess polar and nonpolar sides. The detergent molecules also consist of polar and non-poplar heads and tails. By the detergent molecules only we are able to separate or pull apart the two layers i.e. nuclear and cellular membranes that cause into pouring the DNA into the pea soup.

Answer 4:

If we use 5% isopropyl alcohol instead of 91%:

By using the isopropyl alcohol we allow the DNA to coagulate. If the concentration is reduced from 91% to 5% it will not be able to successfully coagulate the DNA and the DNA would not be separated from other cell components present in the peas. The correct proportion of isopropyl alcohol used helps in separating the DNA into the top layer and the remaining other particles like proteins and other cell parts remain in the water layer present at the bottom.