Definition
               A technique which is used to separate, DNA, RNA or protein pieces from each other under the influence of electric field on the basis of their molecular size is known as gel electrophoresis.
Explanation
                   This method is very reliable for separation of large size molecule (over 1 million Da).  Materials which are required for gel electrophoresis include:
1. TAE stock buffer
2. 1% agrose gel
3. Nucleic acid loading dye
4. Ethidium bromide
Procedure:
                  First prepare a stock solution of TAE buffer by adding appropriate amount of TAE in distilled water. then prepare 1% agrose by adding 1X TAE, some amount of agrose in water and heating it in microwve oven to mix them will. then pour agrose gel on tray and fix comb in it and keep it untill agrose dry. Then remove comb and pour some quantity of nucleic acid along with loading dye and ethidium bromide in each well. EtBr is used for staining nucleic acid. 
When sample is poured in all well also pour  reference marker in one well for comparison. now connect it with voltage for 30-35 min. After this take gel and see it under UV. a large number of nucleic acid pieces will be seen on gel under UV. those pieces which have small molecular weight will cover more distance compared to those having larger molecular weight. 
 
        
                    
             
        
        
        
Explanation:
HIV attacks a specific type of immune system cell in the body. It's known as the CD4 helper cell or T cell. When HIV destroys this cell, it becomes harder for the body to fight off other infections. When HIV is left untreated, even a minor infection such as a cold can be much more severe.
 
        
             
        
        
        
Answer:
Because salt is soluble in water, salt applied to such surfaces dissolves. Liquid water has what is known as a high dielectric constant, which allows the ions in the salt (positively charged sodium and negatively charged chlorine) to separate.
Explanation:
 
        
             
        
        
        
So you don’t tear any tissue and so they get more elastic.