 In the Part B, first of all we will pick the samples from water bath and then add the phenol chloroform iso-amyl alcohol. Now this is our sample after the overnight digestion. After the overnight digestion we will complete the process of DNA extraction which is the Part B. Now we will add the phenol chloroform iso-amyl alcohol in all the samples. The basic purpose of phenol chloroform iso-amyl alcohol is for the phase separation. The basic purpose of iso-amyl in the phenol in PCI is to prevent the forming formation in the interface of the layers. Now we will add the 300 microlitre of phenol chloroform iso-amyl alcohol in all the samples. We will set the pipette at 300 microlitre. The whole chloroform iso-amyl alcohol known as PCI is an organic solution which is light sensitive. Therefore we wrapped it in a aluminium foil. Actually the PCI contains the three components phenol chloroform and iso-amyl alcohol. The ratio of each component is 25 ratio 24 ratio 1. 25 parts are of phenol, 24 parts are of chloroform and one part is of iso-amyl alcohol. We will add the 300 microlitre of phenol chloroform iso-amyl alcohol in our sample. After the addition of phenol chloroform iso-amyl alcohol we will vortex the sample for five minutes. After the vortex we will centrifuge the samples at 13,000 rpm at 4 degree Celsius for 15 minutes. After the centrifugation you will see that there will be the phase separation in the tube. Because the PCI was an organic solution so it separates the DNA from the protein and make the distinct layers. The lower layer which is at the bottom contains the debris and the proteins. Debris are the worn out parts of the cell and the upper aqueous phase contains our DNA. We will transfer the upper aqueous phase into the new Appendorf tube. Per aqueous phase to the new tube we will then add the isopropanol to precipitate the DNA. The basic function of the isopropanol is to precipitate the nucleic acid. So here in this case when we are extracting the DNA the isopropanol will precipitate the DNA. Now we will add the equal amount of isopropanol in the sample. So equal amount means the volume that was of the upper phase we will add the same volume of the isopropanol. The volume of the upper aqueous phase was 500 microlitre so we will add the isopropanol 500 microlitre in the sample. In order to add the isopropanol we will take a pipette of range 100,000 microlitre and set at 500 microlitre. The addition of isopropanol the DNA in the tube will get precipitated and we can analyze the threads of the DNA in the tube. After the addition of isopropanol we will incubate the sample for 5 minutes at room temperature and then we will proceed to the centrifugation with the same condition 13,000 rpm speed for 15 minutes at 4 degree Celsius. After the centrifugation the DNA will be settled down and we will discard the supernatant and then wash the pallet with the chilled ethanol. Now we will add the 500 microlitre of ice chilled ethanol in order to wash the DNA pallet to remove the remaining contamination. We will set the pipette at 500 microlitre in order to add the ice chilled ethanol. After the addition of ice chilled ethanol we will again centrifuge the sample at 8,000 rpm for 7 minutes at 4 degree Celsius. After the centrifugation we will discard the supernatant and then air dry the pallet. After the air drying of samples I have added the nucleus free water and now we will store the DNA at minus 20 degree Celsius.