Answer:
Gene therapy is a medical field which focuses on the utilization of the therapeutic delivery of nucleic acids into a patient's cells as a drug to treat disease.
 
        
                    
             
        
        
        
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The answer to this question would be: half of
Gametes cell is a haploid cell that only has half of genetic material from the parent cells. The process of making gamete cells is called meiosis.
The gamete is haploid because it was used in fertilization and need to fuse with other gametes(example: sperm with the egg) resulting in a full paired chromosomes.
        
             
        
        
        
The procedure of dialysis maintains the body in balance by withdrawing waste, extra water, and salt by preventing them from accumulating up in the body when the kidneys fail. It helps in maintaining a safe level of some kinds of chemicals in the blood, like sodium, potassium, and bicarbonate. It helps in monitoring blood pressure.  
Hence, dialysis helps in performing a function for the circulatory system of the body.  
 
        
             
        
        
        
The true answer of your question is : 
OH : HYDROXYL GROUP
NH2 : AMINO GROUP
CH3 : METHYL GROUP ( but in rather broader terms, that functional group of formula CnH2n+1 where n is an integer is called ALKYL GROUP where by substituting n by 1,2,3... we obtain methyl for n = 1, ethyl for n = 2, and propyl for n = 3 )
COOH : CARBOXYL GROUP is the correct answer since carbonyl is characterized by the presence of functional group C=O in general the formula of the compound would be 
R-C=O-R’ where R and R’ are alkyl groups like methyl for example. However the carboxyl group could be thought of as a summation of carbonyl + hydroxyl ( CO + OH ) resulting thus in COOH. 
I hope you’ll understand everything, anyway if not i’m always here to help. ♥️