The creation of DNA fragments with ends that can join with other DNA is achieved by the use of restrictive enzyme analysis.
<h3>What are restriction enzymes?</h3>
They are enzymes utilized in genetic engineering or gene recombination technology to cut DNA at some specific points in other to have sticky ends.
The sticky ends DNAs are able to join with other DNAs using these ends. Another enzyme (Ligase) is utilized to join the DNA back once the desired DNA has been inculcated.
More on restriction enzymes can be found here: brainly.com/question/13944056
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Germ-line mutations are mutations that would be passed down to future generations, and recombinations are where the information each parent passes down to the offspring is shuffled. 
The genetic variation would have to come from random events: False
Only alternate generations would express any genetic variable: False
Body cell mutations would be the only source of heritable genetic variation: False
There would be no new heritable genetic variation possible in the population: True
        
                    
             
        
        
        
<h2>Urea </h2>
Explanation:
Urea is a small nitrogenous compound which is the main end product of protein catabolism in mammals 
- Urea is a nitrogen-containing substance normally cleared from the blood by the kidney into the urine
- It is made predominantly in the liver from ammonia and bicarbonate and is one of the main components of urine
- The rate of synthesis varies from 300 to 600 mmol/day depending on the protein intake
- All of this urea eventually finds its way into the urine
- Because urea makes up a large part of the obligatory solute excretion, its osmotic pressure requires significant volumes of water to carry the urea
- Urea passively crosses biological membranes, but its permeability is low because of its low solubility in the lipid bilayer
- Some cells speed up this process through urea transporters, which move urea by facilitated diffusion
- Urea is passively reabsorbed in the proximal tubule, but its route of transport is not clear
- Urea transporters have not yet been identified for the proximal tubule